seedling functional type is the study of the morphology of the seedlings in relation to the cotyledon function

1. A SEMENER ON
SEEDLING FUNCTIONAL TYPE
UNDER THE SUPERVISION OF DR. PANNA DEB.
DEPARTMENT OF ECOLOGY AND ENVIRONMENTAL SCIENCE
PREPARED BY-
JINTU KUMAR BANIA
M.Sc 2nd semester
Roll no: 10
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2. INTRODUCTION
• Seedling functional types refer to morphology of
seedlings in relation to cotyledon function and
position. It is a categorical trait that can be used to
characterize plant regenerative strategies. The
distribution of seedling traits across families is still
rather poorly known, although the importance of
seedling traits in systematic was recognized quite
early. This trait has been created on the basis of
woody species (trees and shrubs) and has been
mainly used in tropical forests.
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3. What is seed?
• A seed is an embryo plant wrapped in a protective
covering of maternal tissue ( the testa).
• It is generally provided with nutrient in a separate
tissue ( the endosperm ).
• The primary function of the seed is reproduction.
• An important feature of the seed is their genetic
variability. But some seeds are clonal, because a
number of plants are evolved by means of producing
seeds without meiosis or fertilization.
• Seeds are result of sexual reproduction.
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4. Seedling.
• A seedling is a very young plant that grows from a
seed. When the moisture, light, and temperature
conditions are correct, the seedling's development
begins.
• Seedling development is begins with germination
and the formation of three main parts-
– Radicle - Embryonic root
– Hypocotyl - Embryonic shoot
– Cotyledons - Seed leaves
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5. Cont.
• Seedling emergence and establishment are
critical early plant life cycle stages
• The vast majority of dispersed seeds fail to
emerge as seedlings.
• Seeds buried in the soil tend to have a more
or less exponential decay, some are eaten,
and some are attacked by the pathogens and
another possible fate is germination at depths
that are too great to permit emergence.
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6. Seedling establishment
• Seedling perhaps the most critical stage in the
life cycle of the plant.
• Seedling establishment represents the final
hurdle in the process of regeneration.
• The start of the seedling phase may be
defined by the completion of germination.
• In most of the cases seedling establishment is
marked by the extrusion of the Radicle (root)
and followed by the Plumule (shoot).
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7. • The seedling is equipped with a multitude of
sensors, that provide the information about
the environment in which it is growing.
• A tropism is defined as the directional
movement of plants in response to a
unilateral stimulus. Two most crucial signals
are the-
– Gravity
– Light
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8. Fig: Successive stages of hypogeal germination of dicotyledonous exalbuminous seed
of pea
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9. When does a seedling cease to be a
seedling?
• The point at which the cotyledons (or
endosperm) cease to lose weight.
• The point at which independent survival is
possible, even if the cotyledons (or
endosperm) are removed.
• The point at which an agreed percentage (e.g.
90%) of the stored N (or P, K, Mg, etc.) has
been translocated to the embryo.
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10. Seedling Morphology
• The initial morphology of seedlings is
associated with seed size and dispersal
capacity.
• Seedlings fall into two main groups according
to the position of the cotyledons relative to
the ground after germination.
– Hypogeal species
– Epigeal species
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11. Hypogeal species
• In the hypogeal species, the cotyledons
remain at or below the soil and act only as
nutrient reserve, decreasing steadily in
weight as the nutrients are translocated to
the embryo.
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12. 12

13. Epigeal species
• In epigeal species, the cotyledons are borne
aloft on a short stem (the Hypocotyl) and are
generally photosynthetic. They expand during
establishment and can gain weight (at least
temporarily) both by carbon assimilation and
by accumulating minerals absorbed by the
roots (Lovell & Moore, 1970, 1971; Milberg &
Lamont, 1997).
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14. 14

15. Cont.
• Seed size is linked to the position of the
cotyledons.
• Small seeds become dependent on external
resources very quickly, and their priority may
therefore be to photosynthesize as soon as
possible.
• In a survey of 209 tree species from the Malaysian
rainforests, all seeds below 3mm in length were
epigeal, and the proportion of epigeal seeds
declines steadily with size (Ng, 1978).
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16. Size class Seed size
(length, cm)
No. of species Species with epigeal germination
No. Percentage
1 <0.3 13 13 100
2 0.3-1.0 39 31 79
3 1.0-2.0 74 48 65
4 2.0-3.0 43 13 53
5 3.0-4.0 19 9 47
6 4.0-6.0 18 10 55
7 6.0-8.0 03 0 0Table 1.0: Seedling morphology in relation to seed size in 209 Malaysian tropical tree
species. The percentage of epigeal species declines steadily with seed size. Data from
Ng (1978) 16

17. Cont.
• Beside from the two type of the seedlings
(Epigeal & Hypogeal), NG(1978)
recognized two other type of the seedlings
among the tropical forest, namely-
– Semi-hypogeal
– Durian
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18. Seedling mineral requirements
• One of the functions of a seed is to
provide the embryo with a reserve of
mineral and organic nutrients to nourish it
in the initial stages of establishment.
– Larger seed- Greater absolute of nutrient
reserves
– Smaller seed- Higher concentration of
nutrient reserves.
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19. Cont.
• The gross measurements of absolute
elements in the seed tells about the
amount available to the embryo.
– Some minerals make the seed coat.
– Some are use for structural and for functions.
And this minerals are will not available as a part
of nutrient reserve.
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20. Cont.
• Elements like calcium are difficult to translocate
to the embryo.
• For example: In Hakea species, Lamont & Groom
(2002) showed that for seedlings in natural soils,
only 2% of calcium in the cotyledon was transferred
to the embryo (in contrast to 90% of phosphorus).
• The internal supply of N is exhausted very quickly
followed by Ca, Mg, K, P and Fe. And sulphur
generally last for the long.
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21. Limiting factors for seedling
establishment
• Competition with other seedlings.
• With established plant.
• Competition of light, water and nutrients.
• For tree seedling in forest, understorey can
markedly reduce the chances of survival.
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22. Reference
• https://www.maximumyield.com/definitio
n/214/seedling
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