Drought and Its Effect on Okra Production

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  • Topic: Fruit, Okra, Seed
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CHAPTER 2
REVIEW OF LITERATURE
2.1. Drought and its types
Okra (
Abelmoschus esculentus
L. Monech) is an important vegetable grown in
Pakistan and developing worl
d and is equally favourite among the rich and poor. Due to
its flower structure it
is responsive to breed
ing and selection, but l
iterature on the genetics
of drought tolerance in this ve
getable is not freque
ntly available. Drought is a condition
in which soil moisture contents are too low or
tightly attracted by soil particle (due to
lower osmotic potential) so that plant cannot w
ithdraw it or even if it absorbs it cannot
meet its transpiration demands. There are
different types of dr
ought depending upon the
growth stage of plant at which it occurs (Seghatoleslami,
et al.
2007; Sinaki
et al.
2007;
Kron
et al.
2008). The stress that o
ccurs at seedling stage or
during development phase
may be called as early drought. Such type of
drought usually reduces the crop stand and
as a result it damages yield due to lo
wer than optimum plant population (Ashraf
et al.
2005). However, farmers usually respond to this drought by replanting their crops (Muasya and Diallo, 2001). This type of stre
ss has been proved leth
al for early maturing
varieties (Muasya and Diallo,
2001), which seldom recover fr
om the stress while late
maturing varieties have enough time to recover.
Drought occurring during vege
tative growth period is ca
lled as vegetative phase
drought. This type of drought affects plants
assimilatory organs, which usually decrease
in number and size resulting in lower photos
ynthates production (Kaiser, 1987; Chaves,
1991; Larcher, 1995; Chaves
et al.
2002). As a result yield
decreases due to less amount
of assimilate availabl
e to the developing pods.
The third type of stress de
velops during bud formation, fl
owering and grain filling
period. It reduces yield due to
abortion of ovule, embryo and sterility of pollen. Review
of previous...
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