Interactive effects of high temperature and elevated carbon dioxide concentration on cowpea [Vigna unguiculata(L.) Walp.]

Abstract

Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive failure under heat stress. Heat stress affects two stages of reproductive development in cowpea [Vigna unguiculata (L.) Walp.], and genotypes are available with tolerance and sensitivity to heat during these different stages. The objectives of this study were to determine the responses of these cowpea lines to ambient and elevated [CO2], under heat stress and optimal temperature, and test whether differences in carbohydrate supplies due to genotypes, CO2 enrichment and heat stress are associated with differences in sensitivity to heat during reproductive development. Plants were grown in reach‐in growth chambers and subjected to day/night temperatures of either 33/20 or 33/30°C, and [CO2] levels of either 350 or 700 μmol mol‐1. Under intermediate night temperature (33/20°C), all lines set substantial numbers of pods. Under high night temperature (33/30°C) with either ambient or elevated [CO2], one heat‐sensitive line produced no flowers and the other set no pods, whereas the heat‐tolerant line abundantly set pods. High night temperature reduced the overall carbohydrate content of the plants, especially peduncle sugars, and caused decreases in photosynthetic rates. The high pod set of the heat‐tolerant line, under high night temperature, was associated with higher levels of sugars in peduncles compared with the heat‐sensitive lines. The heat‐tolerant line accumulated substantial shoot biomass, exhibited less accumulation of starch in leaves, and possibly had less down‐regulation of photosynthesis in response to CO2 enrichment and heat stress than the heat‐sensitive lines. Elevated [CO2] resulted in higher overall carbohydrate levels in heat‐sensitive lines (starch in leaves, stems and peduncles), but it did not increase their heat tolerance with respect to flower production or pod set. Heat‐induced damage to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles, indicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat‐tolerant line was the most responsive genotype to elevated [CO2] with respect to pod production under either high or intermediate temperatures.

Projected change in climate thresholds in the Northeastern U.S.: implications for crops, pests, livestock, and farmers

“…montana), whose presence is limited in the northern states by winter low temperatures (Bunce and Ziska 2000). Alternatively, greater increases in summer night-time relative to day-time temperatures projected with global warming (McCarthy et al 2001) could decrease seed production to a greater extent in crop relative to weed species (e.g., cowpea, Vigna unguiculata, Ahmed et al 1993) with subsequent competitive effects. Differential responses of seed emergence to temperature could also influence species establishment and subsequent weed/crop competition (e.g., Houghton and Thomas 1996).…”

Sensitivity of flowering plant gametophytes to temperature fluctuations

“…In some studies of floral abortion under temperature stress, the observed reduction in carbohydrate supply to the reproductive tissues was attributed rather to reduction in sink demand (e.g. abscission of reproductive structures) than to assimilate supply by photosynthetic tissues in tomato (Dinar and Rudich, 1985), pepper (Aloni et al, 1991), and cowpea (Vigna unguiculata L.) (Ahmed et al, 1993). Thus, without neglecting the importance of vegetative growth as the source of nutrients and reserves for sink reproductive structures, it seems that small temperature fluctuations -in magnitude and span-that do not necessarily result in great effects on vegetative growth and photosynthetic activity, could be a limiting factor for the likelihood of a flower to set seeds.…”

Climate Change: Seed Production and Options for Adaptation

“…Genetic diversity for heat tolerance has already been demonstrated for crops such as wheat [124], soybean [125], peanut ( [126,127], Table 2), bean [128], cowpea [129], and cotton [130]. Breeders could also consider incorporating photoperiod insensitivity [131] so that seed filling can begin before the onset of the highest temperatures [132].…”