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Cones

The document discusses different types of trees. It notes that there are over 60,000 tree species worldwide, with the greatest diversity found in tropical regions that are still being surveyed. The majority of tree species are flowering plants, with about 1,000 species of conifers and related gymnosperms. Angiosperm trees can be divided into eudicots and basal angiosperms including magnolias. Wood provides structure and allows trees to transport water and nutrients throughout the plant. Trees are either evergreen, retaining foliage year-round, or deciduous, shedding leaves seasonally.

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49 views2 pages

Cones

The document discusses different types of trees. It notes that there are over 60,000 tree species worldwide, with the greatest diversity found in tropical regions that are still being surveyed. The majority of tree species are flowering plants, with about 1,000 species of conifers and related gymnosperms. Angiosperm trees can be divided into eudicots and basal angiosperms including magnolias. Wood provides structure and allows trees to transport water and nutrients throughout the plant. Trees are either evergreen, retaining foliage year-round, or deciduous, shedding leaves seasonally.

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Illavarasan
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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might total twenty-five per cent of all living plant species.

[19][20] The greatest number of these grow in tropical regions


and many of these areas have not yet been fully surveyed
by botanists, making tree diversity and ranges poorly
known.[21]

Tall herbaceous monocotyledonous plants such as banana lack secondary


growth, but are trees under the broadest definition.

The majority of tree species are angiosperms. There are


about 1000 species of gymnosperm trees,[22] including
conifers, cycads, ginkgophytes and gnetales; they produce
seeds which are not enclosed in fruits, but in open
structures such as pine cones, and many have tough waxy
leaves, such as pine needles.[23] Most angiosperm trees are
eudicots, the "true dicotyledons", so named because the
seeds contain two cotyledons or seed leaves. There are
also some trees among the old lineages of flowering plants
called basal angiosperms or paleodicots; these include
Amborella, Magnolia, nutmeg and avocado,[24] while trees
such as bamboo, palms and bananas are monocots.

Wood gives structural strength to the trunk of most types of


tree; this supports the plant as it grows larger. The vascular
system of trees allows water, nutrients and other chemicals
to be distributed around the plant, and without it trees
would not be able to grow as large as they do. Trees, as
relatively tall plants, need to draw water up the stem
through the xylem from the roots by the suction produced
as water evaporates from the leaves. If insufficient water is
available the leaves will die.[25] The three main parts of
trees include the root, stem, and leaves; they are integral
parts of the vascular system which interconnects all the
living cells. In trees and other plants that develop wood, the
vascular cambium allows the expansion of vascular tissue
that produces woody growth. Because this growth ruptures
the epidermis of the stem, woody plants also have a cork
cambium that develops among the phloem. The cork
cambium gives rise to thickened cork cells to protect the
surface of the plant and reduce water loss. Both the
production of wood and the production of cork are forms of
secondary growth.[26]

Trees are either evergreen, having foliage that persists and


remains green throughout the year,[27] or deciduous,
shedding their leaves at the end of the growing season and
then having a dormant period without foliage.[28] Most
conifers are evergreens, but larches (Larix and Pseudolarix)
are deciduous, dropping their needles each autumn, and
some species of cypress (Glyptostrobus, Metasequoia and
Taxodium) shed small leafy shoots annually in a process
known as cladoptosis.[5] The crown is the spreading top of

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