Mohamed Anverkhan Shahfeek Ahamed maruthamunai +94758545135

1. MA.SHAHFEEK AHAMED
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2.  What is Leaf senescence?
last stage of leaf development
 Involves -leaf decay
-removal of the nutrients that are
stored – leaves other parts
 Although overall leaf senescence- organ
level but heavily influence by cell organism
level
 Altruistic process- gene expression,
metabolism and cell structure.
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3.  Leaf senescence involves age dependent
programmed cell death
 Major changes-break down of the chloroplast
and cell structure
 The decay of leaves and transfer of nutrients
to seeds in crop species such as Maize.
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4.  leaf senescence leads to better
controll of the nutrients. that are
available to the plants,and allows
these to be used at correct time.
◦ To give the plant an evolutionary
advantage.
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5.  The senescence influenced by several
phytohormones with cytokinin and ethylene-
most extensively documented
 Abscisic acid, auxin, also effect on the
senescence
 Major ways-control-plants
◦ Hormone bio synthesis
◦ signaling path ways
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6.  Cytokinin
◦ Strongest effect – on the retardation of leaf
senescence.
◦ Application retard –preventing the chlorophyll break
down
◦ The drop in cytokinin levels before the onset of
senescence in believed to be a key signal for the
initiation.
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7.  Auxin
◦ The diversity of the auxin responses is reflected
by the existence of multiple.
◦ It retard-soyabean-senescence(leyser,2004)
 Gibberalic acid
◦ It promote stem and leaf growth
◦ Induce seed germination.
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8.  Ethylene
◦ Important role in plant growth and development
from seed germination to organ senescence
◦ Key hormone in regulating the onset of leaf
senescence
 Absicsic acid
◦ Related to seed development and seed
germination.
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9.  Control by multiple developmental and
environmental signal
 Identification of genes that show enhanced
expression during senescence.
 Arabidopsis has been very fruitful in revealing
the molecular genatic nature.
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10.  Last stage – leaf development- senescence
 Better control of the nutrients.
 Senescence involves – break down of the
chloroplast.
 Regulation of leaf senescence by cytokinin &
ethylene.
 Control of leaf senescence is done by
hormonal and molecular and geneticaly.
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