Extreme Temperature Responses, Oxidative Stress and Antioxidant Defense in Plants - Abiotic Stress: Plant Responses and Applications in Agriculture - page 177

treatments, while in Toyonoka it was much lower at 30/25°C than at 23/18°C. Ripening time
was shorter at 30/25°C than at 23/18°C in both cultivars.

2.8. Yield

As HT negatively affected plant establishment, growth, DM partitioning, reproductive growth
and photosynthesis, it ultimately poses serious consequence on crop yield. Several lines of
study indicated the reduction of crop yield under HT which greatly varies with the degree and
duration of temperature as well as genotypes of the crop (Table 2). Mendham and Salsbury
[82] reported that HT can reduce crop yield by affecting both source and sink for assimilates.
The decrease in grain length and width of cereals was found to be associated with a reduction
in the average endosperm cell area observed under high night temperature [67]. In addition,
cereals generally respond to HT through an increase in the rate of kernel growth, which lead
to a decrease in the duration of DM accumulation [79]. Kernel dry weight reduced from 79 to
95% in field conditions in B-73 inbred line of maize under heat stress [83]. Shah and Paulsen
[84] demonstrated that photosynthesis and leaf area, shoot, grain biomass and sugar contents
of kernels rapidly decreased under HT. High temperature affected the endosperm develop‐
ment in maize and reduced grain yield during endosperm cell division [85]. Prasad et al. [20]
observed that an increase in temperature from 32/22°C to 36/26°C and 40/30°C decreased seed
yield of sorghum by 10 and 99%, respectively. Djanaguiraman et al. [86] grew sorghum plants
both under normal (32/22°C) and HT (40/30°C) and observed significant differences in yield
attributes and yield. After 45 d of treatment, plant height, leaf dry weight, seed weight and
total dry weight decreased by 22, 14, 53 and 36%, respectively compared to optimum temper‐
ature. Compared to other crops, wheat is the most sensitive to HT as the reproductive growth,
especially grain filling is greatly facilitated by LT. Mohammed and Tarpley [87] found almost
90% less grain in the plants grown in high night temperature (32°C) compared to normal
temperature (27°C). Plants grown under high night temperature showed 20% decrease in grain
weight compared to plants grown under normal temperature. Johkan et al. [22] reported that
HT resulted in more immature grains and decreased yields in T. aestivum because of dark
respiration. In a recent study, Prasad et al. [42] observed that spring wheat plants grown under
HT (31/18°C) showed a significant reduction in number of grains spike -1 (50%), total dry weight
(20%), grain yield (39%) and harvest index (24%) as compared to optimum temperature
(24/14°C).

Plant species Temperature and duration % reduction References

35/16°C (day/night), 10 d; during
flower and pod development

Pod plant -1 : 53%
Seed yield: 48%

Cicer arietinum [88]

Main stem pods: 75%
Seeds pod -1 : 25%
Seed weight: 22%

35/18°C, 10 d; during bud formation,
flowering, and pod development

Brassica spp. [89]

35/16°C (day/night), 10 d during early
flowering and pod development

Seed weight: 40%
Harvest index: 7%

Cicer arietinum [90]