Plant Growth and Development
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ÇØÑDÏTÏØÑS ( ËSSËÑTÏÅL ËLËMËÑTS ) FØR GRØWTH
Water: Essential for cell enlargement. Turgidity
of cells helps in extension growth. Water provides
medium for enzymatic activities needed for growth.
Oxygen: It helps to release metabolic energy for
growth.
Nutrients: Macro & micro elements are needed for
the synthesis of protoplasm and act as source of
energy.
Temperature: At optimum temperature, growth is
maximum. Deviation from this may harm the plants.
Light & gravity: Affect certain phases/stages of
growth.
DÏFFËRËÑTÏÅTÏØÑ, DËDÏFFËRËÑTÏÅTÏØÑ ÅÑD RËDÏFFËRËÑTÏÅTÏØÑ
Differentiation is the process in which the cells in meristems (root apical
& shoot-apical) and cambium differentiate and mature to perform
specific functions.
In this, cell walls & protoplasm undergo major structural changes. The
capacity of cell division is lost. E.g. Loss of protoplasm to form a tracheary
element. They also develop very strong, elastic, lignocellulosic secondary
cell walls to carry water to long distances even under extreme tension.
Under certain conditions, living differentiated cells regain the capacity
of division. This is called dedifferentiation, e.g. formation of meristems
(interfascicular cambium & cork cambium) from differentiated
parenchyma cells.
The dedifferentiated cells can divide and produce cells that once again
lose the capacity to divide but mature to perform specific functions. It
is called redifferentiation, e.g., 2° xylem elements, 2° Phloem elements,
cork cells.
Plant growth is open, i.e., it can be indeterminate or determinate.
Differentiation in plants is also open, because cells/tissues arising out of
the same meristem have different structures at maturity.
Final structure at maturity of cell/tissue is also determined by the
location of the cell. E.g. cells positioned away from root apical meristems
differentiate as root cap cells, while those pushed to the periphery
mature as epidermis.