Agriculture Reference
In-Depth Information
Both high and low temperature stresses can affect seed
germination, seedling survival, photosynthesis, mem-
brane function, and protein and hormone function.
Cold stress encourages a prolonged vegetative period
but high temperatures reduce the vegetative period.
growth on the styles of sensitive genotypes was retarded
due to cold temperatures. Short pollen tube length at
low temperature (15°C) in in vitro germination tests was
observed at 20°C and 25°C by Savithri et al. (1980).
Ultimately pod set is reduced by low temperature as
observed by Srinivasan et al. (1999). They found that
pod set was reduced at a low temperature regime of
15/5°C compared with the control (25/15°C).
High temperature during the reproductive stage is a
major cause of yield loss due to partial or complete
pollen sterility. In chickpea, temperatures at or exceeding
35°C affected male reproductive tissue (anther and
pollen), function (pollen germination and tube growth)
and pod set. Both anther and pollen showed more struc-
tural abnormalities under stress including changes in
anther locule number, anther epidermis wall thickening,
and pollen sterility rather than functional abnormal-
ities (e.g. in vivo pollen germination) (Figure  5.1)
(Devasirvatham et al., 2013). Pollen abnormalities can
also be found at high temperature, including leakage of
pollen protoplast, zigzag pollen tube growth, pseudo-
germination and bulbous tip formation in the pollen
tube (Devasirvatham et al., 2013). Heat-tolerant chickpea
genotypes had clear pollen tube growth on the style fol-
lowing pollen germination and this was confirmed by
pod set (Figure  5.2). In heat-sensitive genotypes no
pollen germination on the stigma was observed due to
complete pollen sterility at temperatures at or exceeding
35°C (Devasirvatham et al., 2012b, 2013) (Figure  5.2).
Pollen sterility in the heat-sensitive genotypes is a
function of lower sucrose levels, resulting in poor pollen
function and pod set (Kaushal et al., 2013).
At very high temperature (45/35°C) both pollen fer-
tility and stigma function can be affected. Observations
by Kumar et al. (2012b) indicate that oxidative stress in
the leaves results in poor fertilization. Devasirvatham
et al. (2012b, 2013) concluded that the critical tempera-
ture affecting pod set was ≥37°C for heat-tolerant
genotypes (such as ICCV 92944, ICC 1205 and ICC
15614) and >33°C for heat-sensitive genotypes (ICC
5912, ICC 4567 and ICC 10685).
5.2.2 temperature stresses during
the reproductive period
Temperature stress at or around flowering is considered
a major challenge to yield in many chickpea production
areas. Mean daily temperatures at or exceeding 15°C
can cause flower abortion (Clarke & Siddique, 1998).
Temperatures of less than 10°C during flowering induce
flower shedding, low pod set and ultimately poor seed
set. Poor pollen viability and germination are the main
reasons for low pod set (Savithri et al., 1980). The field
and controlled environment screening at ICRISAT
identified chickpea genotypic variation for temperature
stress during the flowering stage. Plants exposed to
mean daily temperatures of 20°C produced more pods
than at 15°C. These experiments identified cold-tolerant
genotypes such as ICCV 88502 and ICCV 88503
(Srinivasan et al., 1998). Cold temperature also reduces
partitioning of assimilates to the vegetative parts, result-
ing in reduced harvest index (HI). This reduction in
harvest index is more common in south Asia and
Australia than other production areas (Siddique &
Sedgley, 1986; Saxena, 1990).
Poor pod set in chickpea can occur due to the failure
of male or female floral parts, or both. Low tempera-
tures at flowering can affect anther dehiscence. Mean
daily temperatures of 15°C can also reduce anther
dehiscence and pollen load on stigma (Srinivasan et al.,
1999). However, at a similar temperature, pollen via-
bility and pollen germination on the stigma were higher
in the tolerant lines ICCV 88501, ICCV 88502 and ICCV
88503 than in the sensitive cultivars Chafa and Annigeri
(Srinivasan et al., 1999). Pollen function was clearly
more sensitive to temperature change than pistil
function (esterase activity). Clarke and Siddique (2004)
showed that pollen viability and pollen germination on
the stigma were the primary reasons why pod set in
chickpea was reduced during low-temperature stress.
Pollen sensitivity to low temperatures was identified at
5 and 9 days before anthesis (Clarke, 2001). Clarke and
Siddique (2004) and Srinivasan et al. (1999) also
observed that low temperature did not affect the pistil
function, i.e. esterase activity. However, pollen tube
5.2.3 temperature stresses during
post-anthesis period
Post-anthesis temperature stress, particularly after com-
mencement of pod set, can cause significant pod abortion
and decreased grain filling. In chickpea, cold stress
decreased the rate and duration of grain filling and
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