Republic of the Philippines

CENTRAL BICOL STATE UNIVERSITY OF AGRICULTURE

San Jose, Pili, Camarines Sur 4418
ISO 9001:2015 www.cbsua.edu.p
h
TÜV-R 01 100 1934918

Laboratory Exercise 3
CULTURAL MGT TO DETER STRESS IN PLANTS OR ANIMALS

Case-in-point (CIP): POTATO

PHYSIOLOGICAL PROCESSES
Growth is the irreversible increase in size and in dry matter due to increase in vegetative or reproductive
parts. It includes increase in number of cells, weight and enlargement of the cells in terms of width, length,
diameter and area.
Development refers to all the changes that the plant undergoes from germination up to before dearth.
Differentiation is the process by which the cells become specialized into recognizable tissues and organs.
Photosynthesis is a biochemical process that serves as the connecting link between solar energy and life on
earth. It is a constructive (anabolic) process by which food of the plant is manufactured from simple
inorganic materials through the agency of chlorophyll; the energy needed is derived from sunlight. In this
process, solar energy is captured and converted into chemical energy stored in the form of carbohydrates.
It is the process where carbon dioxide (CO2) is fixed by the plants.
In C3 plants like potatoes, put CO2 directly into Calvin cycle. Thus the first stable organic compound
formed is glyceraldehyde 3-phosphate. Since the molecule contains three carbon atoms. On hot summer
weather the amount of water that evaporates from the plant increases.

1 ABE 123 (Plant and Livestock Environmental Control Engineering)

 Republic of the Philippines
CENTRAL BICOL STATE UNIVERSITY OF AGRICULTURE
San Jose, Pili, Camarines Sur 4418
ISO 9001:2015 www.cbsua.edu.p
h
TÜV-R 01 100 1934918

Respiration process results in the oxidation of the starch (a polymer of glucose) contained in the cells of
the tuber, which converts it into water, carbon dioxide and heat energy. During this transformation of the
starch the dry matter of the tuber is reduced. The respiration process can be approximately represented by
the oxidation of glucose:

For respiration to occur freely a supply of oxygen is needed and the resulting carbon dioxide and heat have
to be removed from the products' environment. A limited supply of oxygen and inadequate removal of
carbon dioxide may lead to effective asphyxiation and the death of product tissue.

Transpiration is water loss through the skin pores of the tuber and is, effectively, evaporation. Because
roots and tubers are characterized by having high moisture content, even in the ambient conditions
prevailing in the humid tropics, they will continually lose water to the surrounding air. This loss of water
can be significant in several ways. Whilst the original food value may not be affected a large water loss will
adversely affect the quality of the produce, for example a loss greater than 10% will result in a bigger
peeling loss because of the shrivelled texture of the skin and the culinary quality may also be affected.

Translocation- To maintain its metabolic activity, the plant needs to circulate to the various plant parts a
wide variety of compounds. In multicellular plants, the water and inorganic substances absorbed by the
roots have to be transported to the leaves. The sugars and other organic compounds synthesized there
have to be distributed to all parts of the plant, where they are used for growth and maintenance, or stored.
These parts include the parts that we harvest

CULTURAL MANAGEMENT PRACTICES

Field Selection – there are several important factors to consider when selecting the optimal field for
growing the potato crop. Rotation history about both the frequency of potato crops, and also what other
crops have been in the rotation. Remember that volunteer potatoes in adjacent crops will not have
fungicides to prevent late blight spread. Soil type can provide a range of nutrient and moisture availability
to the crop. Certain soil types can allow for earlier planting, require less fertilizers and need less irrigation.
Avoid when possible stony soils as that increases bruising and hence reduces storage life and tuber quality.
If there are low spots in the field have them tiled or consider not planting that area.
Fertility Management – soil type, crop rotational history and variety will all impact what your fertility
management practices should be. It is good to use soil tests and past crop history for the field to be used
when determining what fertilizes materials and rates to use. Be careful to use appropriate application rates
as too little or too much can both cause significant yield and quality problems. Excess nitrogen (N) can
prolong plant maturity, make vine kill difficult, inhibit proper skin set which will make tubers more prone to
soft rot, and reduce dry matter content (specific gravity). Potassium (K) levels are important for tuber

2 ABE 123 (Plant and Livestock Environmental Control Engineering)

 Republic of the Philippines
CENTRAL BICOL STATE UNIVERSITY OF AGRICULTURE
San Jose, Pili, Camarines Sur 4418
ISO 9001:2015 www.cbsua.edu.p
h
TÜV-R 01 100 1934918

quality as low K levels are associated with smaller tuber size, hollow heart, brown center and blackspot.
High levels of K can reduce after cooking darkening and reduce specific gravity.
Weed management - Organic potato producers control weeds largely by cultivation. Good field
preparation, timely pest control and proper seed spacing provide a satisfactory stand that can also reduce
weed competition. In areas with lots of weed pressure, farmers should choose specific potato varieties that
put on a canopy quickly. Hilling, either with an implement or by hand, is a good way to control weeds and
is a necessary component of potato production. Cover cropping is also a good way to reduce weed
populations in your soil and add soil organic matter
Nematode Management - The best strategy for the ultimate suppression of soil borne diseases and
nematodes is selecting a species of mustard that produces large amounts of biomass and glucosinolates.
Also, before incorporating, chop the green manure with a rotary mower or a high-speed flail chopper. The
breakdown of the biofumigant seems to be better in moist soils, so irrigate following incorporation or time
incorporation to occur with a rain.
Disease management - Organic management of viral, bacterial and fungal diseases begins with using
certified seed, employing proper sanitation practices, controlling other plant and insect vectors and using
crop rotations.
Irrigation – is important to provide a longer and less stressful growing environment. Lost growth during the
growing season can never be made up. Also note that plant nutrients can be present in adequate levels for
good productivity, but if the soil is too dry the plant roots cannot absorb the nutrients in sufficient amounts
and so plants will actually be deficient in nutrients.
Seed Source and Handling – it is important to obtain the best quality seed and handle it in an appropriate
manner. Know your seed supplier well – know how they produce and handle their seed. Use certified seed
– this will help minimize bringing disease problems to your farm. Store seed at appropriate and consistent
temperature and relative humidity. Too warm or cycles of temperatures can age the seed prematurely –
this is called physiologically aged seed – which will produce poor stands, less vigorous plants and have
significantly reduced yield. Know about the tuber dormancy of the variety to help plan timing of warm-up,
cutting and planting. Long tuber dormancy varieties may benefit from longer warm-up periods and possibly
pre-cutting several weeks prior to planting.

3 ABE 123 (Plant and Livestock Environmental Control Engineering)

 Environmental Stresses Distinct Manifestations Photo Developmental phase of Solution/Coping Mechanism
Vulnerability
BIOTIC STRESS
Fungi • Early Blight - brown- Tuber Initiation • Practice crop rotation;
Fungi are complex black necrosis on stems, provide proper nutrition
microorganisms that often nonglossy necrotic spots and water; control other
cause plant diseases. Some on leaves, lesions on diseases and insects;
fungi that attack potato live tubers spray or dust with a
in the soil. They enter the fungicide.
plant or tubers through
wounds or through natural
openings, such as lenticels, • Skin Spot - Small, dark • Use disease-free seed;
pustules, about 1 mm in practice crop rotation.
or by direct penetration of
depth, develop on the
the epidermis. Fungi are
tuber. They are dark
disseminated by wind, rain,
brown on the outside
soil, insects, drainage water, and olive brown inside.
infested equipment, and by
• Avoid planting infected
the infected tubers.
seed; avoid use of
• Verticillium Wilt - wilting, infested soil; practice
yellowing, curling and crop rotation; control
rolling of leaves weeds; plant resistant
varieties.

• Wart - characterized by • Eradicate diseased plants;

warty outgrowths on all avoid use of infested
parts of the potato fields; use certified
except the roots. The disease-free seed;

ABE 123 (Plant and Livestock Environmental Control Engineering) 4

 warts occur on buds, the practice sanitation and
bases of stems, the crop rotation; plant
stolons, and on the resistant varieties.
tubers.

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 Bacteria • Blackleg - Yellowing and Tube Initiation  Use disease-free seed;
These organisms are severe rolling of the provide good sanitation;
microscopic. They usually leaves and as the destroy cull piles; and
thrive under warm, moist disease progresses, practice crop rotation.
conditions and are capable dark, inky black, and
of multiplying rapidly. sometimes slimy lesions
Bacteria cause wilting or extend up the stems for
soft rot of potato plants some distance above
and tubers. They normally the ground level.
gain entrance to the plant
via wounds or natural • Brown Rot Use disease-free seed;
 practice crop rotation;
openings. (Southern
Bacterial Wilt) - a slight acidify soil with sulfur.
wilting of the leaves at
the end of the branches
during the hottest part
of the day. Leaves of
affected plants become
pale green and then the
leaflets take on a
bronze color.

Ring Rot (Bacterial Ring Rot) Use disease-free seed;

- wilting of stems, branches,  use whole seed;
and leaves. At the stem maintain strict
end, when tubers are cut sanitation; practice
crosswise, infected tubers crop rotation; plant
show a cheesy rot that is resistant varieties.
gray, creamy yellow or light
to red brown in the area of
the vascular ring.

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 Virus  Calico - large, irregular,  Vegetative growth  Use disease-free seed;
Viruses are complex yellow to cream colored and tuber initiation. rogue disease plants;
proteins. These entities are spots on the leaves, a destroy volunteer alfalfa
invisible without the aid of yellow mottling or plants; control insects.
an electron microscope. blotching of the leaflets,
Most viruses are spread and a slight stunting of
plant growth
from plant to plant by
insects and are tuber
Corky Ring Spot - dwarfed Use disease-free seed;
perpetuated. Other viruses  
with leaves that are avoid infested soil.
are spread by mechanical malformed and mottled.
means, such as by field Some leaves may show an
machinery and by the irregular necrotic
natural rubbing of plants spotting. Brown,
against each other in the concentric rings develop
field. Virus infection can on many of the tubers.
cause necrosis, such as
mottling, top necrosis, and
the classic necrosis of the
phloem caused by leafroll  Leafroll - The leaflets of Plant resistant varieties;
virus, ring spots, and by the lower leaves roll up at  use disease-free seed;
stunting. the edges and become isolate the seed plots;
somewhat papery, brittle, rogue infected plants;
and leathery to the touch. control aphids.
Affected leaves also rattle
if brushed with the hand.
reddish or
purple
discoloration occurs on
ABE 123 (Plant and Livestock Environmental Control Engineering) 7
 the underside of
the leaves. Net
necrosis in tubers.

Nematodes  Lesion Nematode - On Tuber Bulking  Fumigate soil; provide

Nematodes are tiny worms potato tubers pimples good sanitation; practice
that live in soil and water. appear that later change crop rotation; use
Some genera and species of to black depressions. nematode-free seed.
these organisms are parasitic
on potato roots or tubers or
both. Nematodes are
capable of causing mild to
serious disorders. The
severity of disease Use nematode-free seed ;
Potato-Rot Nematode -
development depends on the  appearance of small, practice strict sanitation;
nematode species, practice crop rotation;
grayish patches or
nematode population size, fumigate soil; field dry the
discolored spots or holes.
and the susceptibility of the tubers.
host.

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 Insects  Hopperburn - gradual Vegetative growth and • Control potato leaf
Insects are responsible for dying and a blackening of tuber initiation. hopper with an
two major kinds of damage the tip and margins of the insecticide; control
to growing crops. First is leaflets occur. The leafspot diseases; use
direct injury done to the affected margins roll or cultural practices that will
plant by the feeding insect, curl upward, the leaves ensure adequate soil
dry up, and all dead moisture.
which eats leaves or burrows
tissue becomes very
in stems, fruit, or roots. The
brittle.
second type is indirect
 • Control psyllids with
damage in which the insect Psyllid Yellows - yellowing systemic insecticides.
itself does little or no harm of the margins; upward
but transmits a bacterial, rolling of the basal parts
viral, or fungal infection into of the smaller leaflets;
a crop. rolled leaves usually turn
reddish yellow

ABIOTIC STRESS

ABE 123 (Plant and Livestock Environmental Control Engineering) 9

 Air Pollution  Excess ozone causes a  Maturation  Avoid polluted areas; use
Air pollution has become an dark-brown stippling of varieties that resist this
increasingly severe problem the upper leaf surfaces type of injury.
in man's environment. The of susceptible potato
pollution of the air causes plants. PAN produces a
appreciable injury to many silvering or glazing on the
lower surfaces of
crops, including potatoes.
affected leaves
The atmospheric impurities
that damage potatoes are
ozone and PAN (peroxyacetyl
nitrate).

High-nitrogen concentrations  Fertilizer Burn - lack of Vegetative Growth  Place highly concentrated
In certain potato-growing vine growth and nutrients far enough from
areas, particularly those darkening of vine color. the potato seed piece to
where furrow irrigation is There is also a general avoid injuring the roots,
used, high concentrations of lack of vigor in the period but close enough for
nitrogen in contact with seed of early growth irrigation water to
pieces and potato roots can dissolve the nutrients and
cause seed-piece decay and move them into the root
root burning. zone. The water level
must be considered in
relation to fertilizer
placement so that soluble
nutrients are made
available to the plant.

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 Sunlight/Artificial Light  Sunburn, or greening, Tuber Bulking  Hill plants properly in
Light intensity influences results from the field; store tubers in
photosynthesis and also has exposure of the tubers complete darkness;
some formative effects on to sunlight during market tubers in
growth and development of growth or after digging, lightproof containers;
the potato plant. and to artificial light rotate potato tubers on
during holding periods display in market.
on display stands.

ABE 123 (Plant and Livestock Environmental Control Engineering) 11

 High Temperature  Sunscald - Sunscald is an Tuber initiation  Prevent exposing tubers
High temperatures during environmental effect to the sun for
tuber initiation increase the that causes parts of prolonged periods of
respiration rate using up young, tender leaflets to  time.
energy and reducing tuber become light green, Tolerance mechanisms
set. A high respiration rate wilt, then dry up and
mid-season or later may become tan. In tubers,
cause the production of a
frequent exposure to
second set of tubers which
sunlight and the
never size up — high
temperatures during resulting high
bulking slow down tuber temperatures result in
bulking resulting in yield the killing of some tuber
losses. cells. Often affected
tubers become watery
and turn brown to a
considerable depth or
throughout the entire
tuber.

Low Humidity  Tipburn- condition that Tuber initiation  Conserve soil moisture;
Soil moisture and its develops when control insects.
availability to support plant excessive amounts of
growth is a primary factor moisture are lost from
in farm productivity. Too plant tissues during
little moisture can result in periods of hot, dry
yield loss and plant death. weather. Yellowing of
the tips and margins of
the leaflets, then a
gradual dying and

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 browning or
blackening of these
parts.
Flooding  Tuber lenticels will Tuber Initiation  The most common
Flooding causes oxygen in enlarge, increasing the coping mechanism
the soil to decrease and risk of bacterial soft toward flooding is the
not be available to the rot, pythium leak and development of
roots, resulting in oxygen pink rot. Tubers adventitious roots.
deprivation. It is associated harvested after late- These roots have a high
with compacted soil and season flooding do not porosity that helps in
low areas with poor store well and break the uptake of water and
drainage. Early season down. nutrients under the
flooding may reduce and submerged state.
delay emergence, and During flooding when
promote stem rots, plants are unable to
blackleg and stem/stolon avail oxygen for aerobic
canker. Mid- and late respiration, they
season flooding may maintain cell viability by
reduce yields and increase shifting toward
mis-shaping of tubers. anaerobic, glycolytic,
and fermentative
metabolism.

ABE 123 (Plant and Livestock Environmental Control Engineering) 13

 Republic of the Philippines
CENTRAL BICOL STATE UNIVERSITY OF AGRICULTURE
San Jose, Pili, Camarines Sur 4418
ISO 9001:2015 www.cbsua.edu.p
h
TÜV-R 01 100 1934918

References:

Don Halseth (2014). Best Management Practices for Potatoes. Department of Horticulture Cornell
University. Retrieved from http://www.hort.cornell.edu/

Dufour, Rex et al (2009). Potatoes: Organic Production and Marketing. A Publication of ATTRA— National
Sustainable Agriculture Information Service.

CROPWATCH. Potato Education Guide. Institute of Agriculture and Natural Resources. Retrieved from
https://cropwatch.unl.edu/potato-education-guide

O'Brien, M.J. and Rich, A.E. 1979. Potato Diseases. Agriculture Handbook No, 474. Washington, D.C.

Vizmonte, P. Jr. and Canare,J. Jr. Physiological processes affecting crop production. CRSCI 1100Principles
of Crop Science.

Tewari, Sakshi. 2018. Flooding Stress in Plants and Approaches to Overcome. doi: 10.1016/B978-0-
12812689-9.001

Submitted by: Angelica Mae P. Cornejo

 BSABE 4M

ABE 123 (Plant and Livestock Environmental Control Engineering) 11