Climatic factors, Hormones

and Developmental
Physiology of Tropical Fruits

Submitted to – Dr. A.K.Godara

Submitted by – Abhilekh(2023A62M)
Savin Rani(2023A65M)
Shelly (2023A66M)
Mukesh (MHU2023H07M)
Rooma (2023A150M)
CCS Haryana Agricultural University
CCS Haryana Hisar (125004)
Agricultural
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 Introduction
• Climate:- Climate is the average weather pattern in a specific area over a long period
of time at least of 30 years.
• Climate change:- UNFCCC(United Nations Framework Convention on Climate
Change)defines climate change as a “a change of climate which is attributed directly
or indirectly to human activity that alters the composition of the global atmosphere
and which is in addition to natural climate variability observed over comparable time
periods.
• Various climatic factors affecting the growth and development of tropical fruit
crops:-
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1. Light.
2. Temperature.
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3. Water.
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4. Gases.
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5. Air pollutants etc.

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 How does light affect plant?
• Plants have adapted, over millions of years, to use sunlight as their source of energy .
• They do this using a pigment called chlorophyll to photosynthesize.
• Plants use light in the visible light spectrum – a narrow band of radiant energy that we can see with
our eyes.
 A plant response to light will vary depending upon the intensity, duration and wavelength of light.
1) Light Intensity:
 Refers to the concentration of light waves striking the leaf surface.
 Expressed in foot candles.
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 Higher where there are no clouds & little moisture in air.

 It varies with elevation , latitude, season & weather condition.
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
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2.) Light Duration: It controls flowering.

 3) Wavelength: Plants respond to light of wavelengths from 300-800 nm.
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Light reactions of plants are carried on by different pigment systems that absorb specific wavelengths of
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light, i.e. Blue, green or red light. Chlorophyll absorbs light in red & blue portions of spectrum
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 • Effect of light intensity on leaf structure and growth of Mangosteen seedlings:-Mangosteen (Garcinia
mangostana L.) is a tropical fruit crop originating in South-east Asia, growing in humid and shaded environmental
conditions. Young mangosteen seedlings were grown under 25, 40, 55 or 100% of light intensity for two years. An
increase of light intensity increased the thickness of lamina resulting in an increase of palisade and spongy tissues
and the stomata frequency also increased. Both chlorophyll a and b declined gradually as the light intensity
increased and the average ratio was 0.808. The growth of seedlings described as leaf size, leaf number per plant,
total leaf area, height, fresh weight and dry weight were dramatically reduced when exposed to 100% light
intensity condition. Maximum growth was found when exposed to 40% light intensity condition. Dry weights of
seedlings grown under 25, 40, 55 or 100% of light intensity were 161.7, 201.5, 150.1 and 11.7 g per plant,
respectively
Reference:-https://www.actahort.org/books/787/787_34.htm
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• Effect of prolonged solar exposure on the vitamin C contents of tropical fruits:-Five groups of fruits: mango,
melon, orange, papaya, and pineapple were exposed to sun from 8 a.m. To 6 p.m. Simulating open marketing
practices in the tropics. Their internal temperatures were recorded every 30 min and samples were analysed for
vitamin C and total soluble solids every hour. Internal temperatures of the fruits were considerably higher than the
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ambient temperature and the differences ranged from 8·1 to 11·1°C. The level of vitamin C declined considerably
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(20–56%) until about 1 p.m. Followed by an unexpected upsurge reaching close to the initial or even higher value
by 6 p.m. On average the total soluble solids, during solar exposure, gradually increased by about 14% of their
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initial values. Reference:-https://www.sciencedirect.com/science/article/pii/0308814693902244

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 How does temperature affect plant growth?
Both air and soil temperatures have an impact on plant growth.
Air temperature influences leaf temperature and therefore the rates of photosynthesis, respiration, and
other metabolic reactions.
On the other hand, soil temperature influences germination, root development, and nutrient uptake.
All of the chemical reactions in a plant, including photosynthesis and respiration, fall under a term,
metabolism.
• The speed at which metabolism occurs is affected by temperature.
• Cool temperatures slow metabolic processes, while warmer temperatures speed the processes.
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• Most plants show optimum growth when night temperatures are 10 to 15 degrees cooler than day
temperatures.
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• Under ideal conditions photosynthesis occurs at a high rate during the day.
• The cooler temperatures at night slow respiration.
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• For growth to occur, the rate of photosynthesis must exceed that of respiration.
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• High temperatures can speed the rate of respiration beyond that of photosynthesis.
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 • Effects of high temperature:- i) Desiccation or drying.
• (ii) Water balance of the plant is disturbed resulting in temporary or permanent wilting.
• (iii) Dehydration of protoplasm, which results in slowing down of all life processes or even death.
• (iv) Scorching or burning of plant organs.
• (v) Chemical effects like denaturation and precipitation of proteins, and metabolism of fats and
carbohydrates.
(vi) Stem girdling (killing or damaging the meristem) from hot soil surface.
• Effects of low temperature:-
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1. Biological processes in the plant body slowed down.

2. Decreased root membrane permeability.
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3. Ice crystals form in the intercellular spaces which result in squeezing and distortion of plant cells.
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4. Desiccation.
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5. Frost cracks.
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 Effect of temperature on the flowering biology and fertilization of mangoes

• The effect of 3 temperature regimes (31/25 (warm), 25/19TARI. (moderate) and 19/13°C (cool),
day/night) on flowering and Pollination in 4 mango cultivars (Haden, Irwin, Keitt and Local) was
investigated in Taiwan. Compared with the moderate treatment, warm temperatures hastened growth
rates of panicles and flowers, shortened flowering duration and life span of individual flowers, and
decreased the number of hermaphrodite and male flowers. Warm temperatures increased the rates and
percentages of anther dehiscence and pollination. In contrast, cool temperatures retarded the growth of
panicles and flowers, extended flowering duration and life span of flowers, and increased the number
of hermaphrodite and male flowers. Sex ratio was statistically not different among the 3 temperature
treatments. The highest number of hermaphrodite flowers occurred during the first third of the
flowering period.
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Reference :- SHU, Z.H. effect of temperature on the flowering biology and fertilization of
mangoes(Mangifera indica L.). Journal of Applied Horticulture(Lucknow)(1999)1(2)79-8n[En,27 ref.]
Fengshan Tropical Horticultural Experiment Station, TARI, Fengshan, Kaohsiung 830 Taiwan.
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 Effect of temperature on ripening of “Chinn Hwang”Mango

• In one experiment in central Taiwan, Chiin Hwang mango fruits were harvested 93 days after full
bloom and were placed at 25°C or 38°C for ripening. In another experiment fruits were gathered 102
days after anthesis and were stored at 28°C or 38°C, to Results compare the ripening process under
different temperatures. indicated Chiin Hwang fruits were unable to complete the ripening process in
up to 4 days at 25°C, while ripening was accelerated at 38°C. Two days after treatment (38°C), soluble
solids increased to 11.2%, firmness and starch content decreased gradually as total soluble sugar
concentration and a-amylase activity rose. Four days after treatment, pulp colour and flavour reached
the stage of maturity but not skin colour. Those fruits picked at day 102, and stored at 28 or 38°C, had
the same degree of maturity and were edible 4 days after temperature treatments. Fruit firmness under
such conditions was 2-4 kg/cm². Total soluble solids stood at 13% or more. There was an increase in
total soluble sugars corresponding to the enhanced activity of a-amylase at 38°C, but relatively less
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significant activity was detected at 28°C. However, fruits ripened at 28°Chad a good skin and flesh
colour: bright orange-yellow at day 6. Those ripened at 38°C also possessed orange yellow skin but
with green patches and some black spots appeared 8 days after treatment. It is concluded that ripening
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at 28°C could retain a better postharvest quality than ripening at 25°C or 38°C.
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 Influence of water
Growing Plants contains about 90% water.
Medium for transfer with in the plants and is solvent system of the cell.
Raw materials for photosynthesis required for the production of new compounds.
In soft tissues water pressure provides support and as plants lose water from their leaves they are cooled.
Takes parts in several chemical reactions.
• A net loss of water will cause growth to stop and continued deficiency results in death
• The plant roots suck or extract water from the soil to live and grow. The main part of this water does
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not remain in the plant, but escapes to the atmosphere as vapour through the plant’s leaves and stem.
This process is called transpiration. Transpiration happens mainly during the day time.
• Water from an open water surface escapes as vapour to the atmosphere during the day. The same
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happens to water on the soil surface and to water on the leaves and stem of a plant. This process is
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called evaporation.
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• The water need of a crop thus consists of transpiration plus evaporation.

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• Therefore, the crop water need is also called “evapotranspiration..

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Response of Grapes to Water-Deficit Stress in
Particular Stages of Development
W. J. Hardie and J. A. Considine
Department of Agriculture, Mildura, Australia, 3500
Abstract
Severe water stress was induced in container-grown
grapevines during five stages of fruit growth. Stress at
each stage reduced fresh fruit yield. During the first
three weeks after flowering, losses were greatest
and were primarily attributable to reduced fruit
set. Thereafter loss was associated with reduced berry
size and, following stress after véraison, the failure of fruit
to mature. Fruit which failed to mature also had a lower
skin pigment content, whether assessed on a per-berry or
per-unit-surfacearea basis.
All fruit from stressed vines was late to mature,
though the delay was greatest for fruit stressed during
the lag phase.
 • Disorders due to deficiency:- Root system: Doesn’t not develop properly,
-Tip burn and drying of root hairs,
- Plant may die.
Leaf: do not attain proper size,
- cutting and mottling of leaves,
- tip burning in tropical fruit crop,
- older leaves get affected first,
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-development of brown or yellow colour of leaf in pear, citrus, peach, plum, cherry
under high temperature .
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- Premature defoliation in deciduous plants under high temp.

Flowering: in banana and pineapple, fruit bud differentiation gets delayed,
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Annual regularity of flowering in mango and litchi is dependent on soil moisture.

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 Disorders due to excess of water:-Root system: infection of fungal and bacterial
diseases on root as well as on the collar zone.
Stem : bark disease, gummosis, In stone and citrus plant formation of gum filled
pockets beneath the bark, False blossom in deciduous plants and malformation in
tropical evergreen plants.
• Leaf : chlorosis yellowing of leaves in apple and peach followed by gummosis and
leads to death.
• Flowering and fruit set: continuous vegetative growth in some tropical and subtropical
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fruit crops.
- Plants bear irregularly, decrease quality of fruits
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• Fruit : take longer time period to mature and ripe

- cracking of fruits in fig, sapota, grape and plum, etc.
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- splitting of skin in banana, date, mango, litchi, etc.

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 Effects of Water Stress on Fruit Quality Attributes of Kiwifruit
S. A. MILLER+, G. S. SMITH, H. L. BOLDINGH and A. JOHANSSON

• The Horticulture and Food Research Institute of New Zealand, Ruakura Research Centre, Private
Bag 3123, Hamilton, New Zealand County Administration Agriculture, S-581 86, Sweden
Abstract
Four-year-old kiwifruit vines (Actinidia deliciosa( A. Chev.) C. F. Liang et A. R. Ferguson
var.deliciosa cv. Hayward) were studied to determine response of the plant and effects
on fruit quality when irrigation water was withheld either early or late in the growing
season. The greatest effect on fruit growth occurred when water was withheld
early in the season. Harvest weight of fruit from early-stressed vines was
approx. 25% less than the weight of fruit on control vines. Early season water
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stress resulted in a transient increase in concentrations of soluble

carbohydrates in both leaves and fruit. This was accompanied by a reduction in
stomatal conductance of the leaves. Starch levels in leaves but not fruit were reduced
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by both stress treatments. Concentrations of sucrose at harvest in fruit from vines

stressed late in the season were markedly higher than in other fruit, and softness of the
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fruit was unaffected. These differences were maintained through the 12 weeks in cool
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storage after harvest. Withholding irrigation water to kiwifruit vines late in the season
may prove a useful management tool to manipulate some quality attributes of the fruit.
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 Hormones
• Hormones – Organic substances produced naturally in
higher plants , controlling growth or other physiological
functions at a site remote from its place of production
and active in minute amounts

Plant hormones
 Auxins
 Gibberellins
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 Cytokinins
 Abscisic Acid
 Ethylene
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 Auxins
• Auxin is a general term used to denote substances that promote
the elongation of coleoptiles tissues.
Major pysiological effects of Auxin are –
Cell Elongation
Apical Dominance-
Root Initiation
Prevention of Abscission
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Parthenocarpy
Respiration
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Callus Formation
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Vascular Differentiation
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 Effect if indolebutiric acid on rooting of
softwood cuttings of Myrciaria jabuticaba
(Brazilian grape tree)

Treatment (dose of IBA (mg/litre)) Percentage of Rooting

0 (Control) No rooting
1000 8.96%
2000 12.88%
4000 23.16%
8000 37.98%
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• Survival of cuttings increased with IBA concentration . Rooted cuttings showed

an average of one root per cutting
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Source – Revista Brasileria de Fruiticultura (1999)

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 Gibberelins –
Major physiological effects of gibberelins are –
Seed germination
Dormancy of buds
Root Growth
Elongation of internodes
Bolting and Flowering
Parthenocarpy
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Light inhibted Stem Growth

De nova synthesis of enzyme  amylase
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 Inhibition of Flowering in Mango(Mangifera
indica) by Gibberelic acid

• Gibberelic acids at concentration of

10~1, 10~2M applied on the buds
of “on” year Dashehri mango tree
just before flower bud
differentiation , inhibited flowering
95% and 75% respectively .
Concentration of 10~3 and 10~4 M
inhibited flowering to a much
lesser extent , but delayed the
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emergence of panical by 2 weeks.

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 Cytokinins -Certain substances which
shows kinetin like activity and promote cell
division are termed as cytokinins
Major physiological effects of cytokinins
Cell division
Cell enlargement
Improve quality and Yield
Initiation of inter-fascicular cambium
Morphogenesis
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Counteraction of Apical dominance

Dormancy of seeds
Delay of senescence – Richmond lang effect
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Promotion of chloroplast development

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 Effect of plant growth regulators on yield and quality of
mango (mangifera indica ) cv. Kesha
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CPPU – N-(-2-chloro-4-pyridyl)-N`-phenyl urea – a synthetic cytokinin

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Source – Journal of Pharmacognosy and Phytochemistry (2017)

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 Ethylene –Hormone with molecular weight of 28 and
is the simplest olefin gas
Major physiological effects of ethylene –
 Fruit ripening
 Plumular hook formation
 Triple response
 Formation of Adventitious roots and root hairs
 Inhibition of root growth
 Lead epinasty
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 Induce flowering
 Sex expression
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 Senescence
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 Abscission of leaves
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 Breaking dormancy of seeds and buds

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 Flowering and fruit set of Haden mango trees
in response to ringing and ethephon and
potassium nitrite sprays

• The effects of ethephone(0.25ml/litre)and potassium

nitrate(30g/litre) sprays , alone or combined , on the flowering ,
fruit set and yield of ringed and non – ringed mango cv. Haden
were investigated . For combined treatments , the number of
ethephone sprays varied (1-3) and ethephone was always applied
before potassium nitrate . The results showed significant effects of
the combination of these products with respect to acceleration
flowering and fruiting , for both ringed and non-ringed trees , but
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more so in non-ringed trees . The treatment with 3 sprays of

ethephon followed by KNO3 gave the best result
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Source – Revista Brasileria de fruiticultura(1999)

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 Developmental physiology and biochemistry of fruits

DORMANCY
Dormancy in plants refers to a state of reduced metabolic activity, growth, and development. During dormancy,
plants enter a period of rest or inactivity, often in response to unfavorable environmental conditions. This phase is
characterized by a temporary suspension of visible growth, including the cessation of shoot elongation, leaf
expansion, and reproductive processes.
There are different types of dormancy, including:
1. Bud Dormancy: The cessation of growth in buds, preventing the development of new shoots or leaves. This is
common in deciduous trees during winter.
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2. Seed Dormancy: Seeds may enter a dormant state, delaying germination until specific conditions, such as
temperature, light, or moisture, are suitable for successful seedling establishment.
3. Reproductive Dormancy: The temporary suspension of flowering and fruiting activities, ensuring that plants
allocate energy to essential processes during unfavorable conditions.
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 DORMANCY
Processes during Dormancy:
Hormonal Regulation:
• Abscisic Acid (ABA): ABA is a key hormone associated with dormancy induction.
Increased levels of ABA are often observed during the transition to dormancy. ABA
inhibits cell division and growth, contributing to the overall suppression of metabolic
activity.
• Ethylene: Ethylene is another hormone involved in the regulation of dormancy. It acts
synergistically with ABA and may play a role in coordinating the dormancy response,
particularly in response to environmental cues.
Carbohydrate Metabolism:
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• Starch Accumulation: Prior to dormancy, tropical fruit trees often accumulate starch as a
storage carbohydrate. Starch serves as an energy reserve and source of carbon for the plant
during the dormant phase.
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• Sugar Signaling: Changes in sugar levels, particularly sucrose, can serve as signaling
molecules during dormancy induction and release. Sugar signaling pathways may
influence the expression of genes involved in dormancy regulation.
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 DORMANCY
Environmental Sensing:
• Photoperiod and Temperature Sensing: Plants sense changes in day length (photoperiod) and temperature,
which act as environmental cues triggering the induction and release of dormancy.
• Chilling Requirement: Some plants, especially in temperate regions, have a chilling requirement, needing
exposure to a certain amount of cold temperatures to break dormancy.
Gene Expression:
• Dormancy-Associated Genes: Specific genes associated with dormancy are upregulated during this phase. These
genes may be involved in stress response, hormone signaling, and the regulation of metabolic pathways.
• Transcription Factors: Dormancy-related transcription factors control the expression of genes involved in
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growth inhibition, stress response, and other processes associated with dormancy.
Dormancy Release:
• Environmental Cues for Bud Break: The release from dormancy often involves exposure to specific
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environmental cues. Warmer temperatures, increased daylight hours, or changes in water availability can signal
the plant to exit dormancy and initiate bud break.
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• Hormonal Changes during Dormancy Release: Dormancy release is accompanied by hormonal changes.
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Gibberellin levels increase, promoting cell elongation and the resumption of growth. Abscisic acid levels
decrease, relieving its inhibitory effects on growth.
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 BUD BREAK
Bud break refers to the developmental process in plants where previously dormant buds undergo growth and
expansion, leading to the emergence of new shoots, leaves, and eventually flowers. This phenomenon typically
occurs in response to favorable environmental conditions, such as increasing temperatures, longer daylight hours,
and suitable moisture levels.
Processes associated with bud break in tropical fruits involve complex interactions among various molecules and
cellular components. Here are the key aspects of bud break in tropical fruits:

Carbohydrate Metabolism:
• Starch Mobilization: Stored carbohydrates, primarily in the form of starch, are mobilized during bud break.
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Starch accumulated in storage organs or within the bud itself is broken down into sugars, providing the energy
necessary for the resumption of growth.
• Sucrose Transport: Sugars, produced through photosynthesis in leaves or mobilized from storage tissues, are
transported to the buds via the phloem. Sucrose, a common transport sugar, is often a key player in this process.
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 BUD BREAK
Hormonal Regulation:
• Gibberellins (GA): Gibberellins play a crucial role in promoting bud break. They stimulate the synthesis of
enzymes involved in cell wall modification and cell elongation. Increased levels of gibberellins are often
associated with the transition from dormancy to active growth.
• Abscisic Acid (ABA): ABA is a growth-inhibiting hormone that tends to decrease during bud break. Its reduction
is essential for overcoming dormancy and allowing the activation of meristems.
• Cytokinins: Cytokinins, along with gibberellins, promote cell division and are involved in the control of bud
growth and differentiation.
Cell Wall Modification:
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• Cellulase Activity: Cellulases are enzymes responsible for breaking down cellulose, a major component of plant
cell walls. Increased cellulase activity is observed during bud break, facilitating the expansion and elongation of
cells in the bud.
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• Pectinases and Hemicellulases: Enzymes such as pectinases and hemicellulases are involved in the modification
of other cell wall components, allowing for the restructuring and growth of cells
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 JUVENILITY
• It can be defined as the physiological state of a seedling plants during which it cannot be induced to flower.
• Depending upon the environmental and genetic factors, juvenile of woody plants may be very short or very long.
• It can be shortened by increasing the growth rate of young seedlings, because a minimum must be attained to
reach the adult stage.
• The juvenile tissue remains in situ at the base of the tree for its entire life. Thus one cut off on 80 year old
seedling tree at the lower trunk, the new growth from latent buds at the base would be juvenile until it once again
grew into the adult phase.
• In constant to seedling plant, commercial cultivar budded on seedling stocks are entirely adult above the bud
union.
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• Rejuvenation : Heavy pruning to old, weak orchard tree done to induce fresh growth is termed as rejuvenation.
Such pruning brings about invigoration (to give energy) but does not return the tree to juvenile phase.
• Transition zone : Zone between juvenile and adult tissue
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 vegetative to reproductive phase flowering
pollination fertilization and fruit set
Type of growth and development
• Vegetative phase: In this phase utilization of carbohydrates takes place. This is the period of growth between
germination and flowering.
• Reproductive phase: It includes the accumulation or storage of carbohydrates. Development of flower bud,
flowers, and fruit set.

vegetative to reproductive phase

• Transitional phase in the life cycle of the plant.
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• Takes place by the transformation of vegetative apex into reproductive structure.

• Shoot meristem is reduced to develop sepals, petals, stamens etc. in the case of leaves.
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• The plant must attain a specific state of ripeness before it flowers.

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 FLOWERING
• The first step of sexual reproduction.
• Flowering leads to succession of events like anthesis, fruit set, fruit maturation and ripening
• A flower is a metamorhosed shoot meant especially for the reproduction of plant.

Events in the bud leading to flowering:

Induction:
• Flowering stimulus is generated
• Influenced by chilling temperature, water stress or photoperiod.
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Evocation:
• Shoot apical has received floral stimulus and irreversibly committed to form flower bud primordia.
Initiation:
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• Evoked bud becomes recognizable as flower bud and is thus committed to reproductive development.
Differentiation of the growing point:
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• Frequency of cell division within the central zone of the shoot apical meristem is increased.
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• Shoot meristem is induced to develop sepals, petals, stamens and carpels in case of leaves.
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 Changes occurring in flowering
Biochemical changes :
i. Development of chloroplast inhibitors
ii. Moving out of floral stimulus from leaves
iii. Increase in total RNA synthesis and chromatins dependent RNA synthesis
iv. DNA synthesis increases
v. Number of mitochondria increases
vi. Starch content decreases
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Metabolic changes :
vii. Meristem height increases
viii.Cell size increases
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ix. Lengthening of mitotic phase (second mitotic peak)

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x. Entry of cell from photosynthetic to mitotic phase

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xi. Flower bud initiation

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 Pollination and Fertilization
Pollination
The transfer of pollen grains from the anther to the stigma of a flower.

TYPES:
Self-pollination/ Autogamy
Cross-pollination/ Allogamy
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Fertilization
• It is the union/fusion of the nuclei of the male and female gametes.
• The pollen grain is the male gamete.
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• The ovule inside the ovary is the female gamete.

• The pollen grain germinates after the pollination of the carpel and it grows through the style by creating
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pathway for pollen grain.

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 Physiological and biochemical changes during pollination and fertilization

• Growing pollen tube increases GA production.

• Increase auxin production by style and then ovary.
• Respiration increase.
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 fruit set, fruit drop, fruit growth, ripening
fruit set and fruit growth
A fruit is a mature ripened ovary.
Fruit set is a critical stage in the life cycle of plants where fertilized flowers develop into mature fruits. This process
involves complex interactions of physiological and biochemical changes. Here are key aspects of the
developmental physiology and biochemistry during fruit set:
Pollination and Fertilization:
• Pollination: Pollen transfer from the male reproductive organ (anther) to the female reproductive organ (stigma)
is crucial for a successful fruit set.
• Pollen Tube Growth: Once pollen lands on the stigma, a pollen tube grows down the style to deliver male
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gametes to the ovule for fertilization.

Hormonal Regulation:
• Auxins: High levels of auxins are often associated with the initiation of fruit set. Auxins influence cell division
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and elongation in the developing ovary.

• Cytokinins: Cytokinins play a role in cell division and influence fruit development.
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• Gibberellins (GA): GAs are involved in promoting cell elongation and fruit growth.
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• Abscisic Acid (ABA): ABA levels may decrease after successful pollination, allowing for the activation of genes
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 fruit set, fruit drop, fruit growth, ripening
Ovary Development:
• Ovary Enlargement: After fertilization, the ovule develops into a seed, and the ovary undergoes significant
enlargement to form the fruit.
• Carpel and Ovule Development: The carpels of the flower enclose the developing seeds (ovules) within the
ovary.
Cell Division and Elongation:
• Cell Division: Rapid cell division occurs in the developing ovary, contributing to fruit growth.
• Cell Elongation: Elongation of cells is essential for the expansion of the ovary and the overall growth of the fruit.
Carbohydrate Partitioning:
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• Sugar Transport: Sugars produced through photosynthesis are transported to the developing fruit, providing the
necessary energy for growth.
• Starch to Sugar Conversion: Starch stored in the fruit may be converted into sugars to support the energy
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demands of fruit development.

Secondary Metabolite Accumulation:
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• Flavonoids and Pigments: Accumulation of pigments contributes to the color of the developing fruit.
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• Phenolic Compounds: Phenolic compounds, including antioxidants, may accumulate, influencing fruit quality.
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 fruit set, fruit drop, fruit growth, ripening
Ripening
includes qualitative changes that occur after the fruit has reached full size. It involves a process in which the
biochemistry and physiology of the organ are altered to influence appearance, texture, flavor, and aroma.

Physiological and biochemical events during ripening:

Ethylene Production and Action:
• Key hormone in fruit ripening, synthesized abundantly during this phase.
• Exhibits autocatalytic effect, inducing its own synthesis in a positive feedback loop.
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• Binds to cell membrane receptors, triggering biochemical responses.

Respiration Rate:
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• Respiration increases, tied to carbohydrate breakdown for energy.

• Some fruits exhibit a climacteric rise in respiration during ripening.
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Starch to Sugar Conversion:

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• Starch undergoes enzymatic hydrolysis into sugars, mainly glucose and fructose.
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• Amylase enzymes play a vital role in starch breakdown.

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 fruit set, fruit drop, fruit growth, ripening
Environmental Stress:
1. Water Stress: Lack of water or drought conditions can induce fruit drop as a survival strategy to conserve
water.
2. Temperature Extremes: Extreme temperatures, especially heat stress, can contribute to fruit drop.

Biochemical Factors:
Enzyme Activation:
3. Pectinase Activity: Enzymes like pectinase break down pectin in the middle lamella, weakening cell
adhesion in the abscission zone.
4. Cellulase Activity: Cellulase enzymes hydrolyze cellulose, further facilitating cell separation.
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Hormonal Regulation:
5. Auxins: A decline in auxin levels is often associated with fruit drop. Auxins inhibit abscission, and their
reduction allows the abscission process to proceed.
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6. Abscisic Acid (ABA): ABA can enhance the sensitivity of the fruit to ethylene, promoting abscission.
Fruit Development Stage:
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7. Maturity: Fruits at a certain stage of maturity become more susceptible to abscission.

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8. Seed Viability: If seeds within the fruit are not viable, the plant may initiate fruit drop to conserve
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resources.
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 fruit set, fruit drop, fruit growth, ripening
Fruit drop
• Fruit drop is the detachment or separation of a fruit from a branch of a tree or a plant, caused by the formation of
a separation of layer of cells on the fruit stalk due to a series of physiological and biochemical events.
Causes of fruit drop
Physiological Factors:
Abscission Zone Formation:
1. Formation: A distinct layer of cells called the abscission zone forms at the base of the fruit stem (pedicel).
2. Cell Expansion: Cells in the abscission zone undergo changes, leading to a weakened connection between
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the fruit and the plant.

Ethylene Production:
3. Role of Ethylene: Ethylene, a plant hormone, plays a crucial role in abscission. It triggers the activation of
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enzymes and processes leading to fruit drop.

4. Ethylene Sensitivity: Fruit tissues become more sensitive to ethylene, initiating the abscission process.
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Nutrient Redistribution:
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5. Resource Allocation: The plant may redistribute nutrients away from the fruit as part of a prioritization
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 Seed development
A seed is small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It
consist of-
Testa: It is the tough hard outer coat. It has to be split open by a radicle before germination can proceed.
Plumule: It is the embryonic shoot. In it, two or more leaves are usually visible, with a growing point enclosed
between them.
Hypocotyl: It is the part of the stem of an embryo beneath the stalk seed of the leaves or cotyledons and directly
above the roots.
Cotyledon: it is the embryonic leaf in the seed-bearing plants, one or more of which are the first leaves to appear
from germinating seeds.
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Type of seed
Starchy seeds: soluble sugar accumulates at the beginning and starch increases reaches highest in the end while
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soluble sugar decreases.

Oil seeds: soluble sugar and starch accumulates in the beginning and then fat accumulates
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 Physiological and biochemical events during
seed development
Physiological Events:
• Double Fertilization: Pollen lands on stigma, leading to egg fertilization for embryo and sperm combining with
polar nuclei for endosperm formation.
• Embryo Development: Zygote divides into embryo; apical meristems form shoot and root systems.
• Endosperm Development: Rapid cell division creates nutrient-rich endosperm with a triploid nucleus.
• Seed Coat Formation: Ovule integuments become seed coat, offering protection.
• Maturation and Desiccation: Seeds accumulate reserves and desiccate for dormancy.
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• Senescence of Parent Tissues: Surrounding tissues senesce, transferring nutrients to the seed.
Biochemical Events:
• Starch and Lipid Accumulation: Endosperm or cotyledons store starch; embryo accumulates lipids for energy.
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• Protein Synthesis: Storage proteins (globulins, albumins) and enzymes for germination.
• Phytohormone Regulation: ABA promotes dormancy; GA breaks dormancy and initiates germination.
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• Polyphenol and Flavonoid Accumulation: Antioxidant accumulation protects against oxidative stress.
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• Cell Wall Modification: Hydrolytic enzymes activate for cell separation during germination.
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