Mechanisms of Reproductive Thermotolerance in Gossypium hirsutum: The Effect of Genotype and Exogenous Calcium Application

Abstract

Although photosynthetic thermotolerance has been investigated extensively in cotton leaves, reports on the biochemical influence of the pistil in promoting fertilization thermostability are limited. To evaluate the effect of temperature, genotype, and exogenous calcium application on fertilization and pistil biochemistry in cotton, thermosensitive (cv. ST4554 B2RF) and thermotolerant (cv. VH260) plants were grown under control (30/20 °C) or high‐temperature (38/20 °C) conditions during flowering, and exogenous CaCl2 was applied to flowers 1 day prior to anthesis. Measured pistil parameters included fertilization efficiency; protein concentration; glutathione reductase, superoxide dismutase (SOD) and NADPH oxidase activities; and ATP and calcium levels. Exogenous calcium had no effect on reproductive thermostability due to poor calcium uptake under high temperature. High temperature resulted in a 19.2 % decline in fertilization efficiency for ST4554 but no change in fertilization efficiency for VH260 relative to optimal temperature conditions. Pre‐stress glutathione reductase and SOD activities were higher in VH260 than ST4554 pistils, and calcium and ATP content were higher in VH260 than ST4554 pistils. It was concluded that pre‐stress antioxidant enzyme activity, ATP and calcium content of the pistil may be associated with reproductive thermotolerance in cotton. These findings should be confirmed in future experiments with a larger number of cultivars.

Involvement of Ca2+ in Regulation of Physiological Indices and Heat Shock Factor Expression in Four Iris germanica Cultivars under High-temperature Stress

“…This study applied the Ca 2+ antagonist LaCl 3 to 'Music Box' and 'Galamadrid', which have stronger high-temperature tolerance than the other two cultivars studied. Results are consistent with previous reports in that LaCl 3 plays a negative role in promoting the activity of antioxidant enzymes and increases proline and soluble protein (Gong et al, 1997;Liang et al, 2009;Snider et al, 2011). Moreover, LaCl 3 -sprayed leaves were found to accumulate more MDA than leaves that had undergone water treatment.…”

Increased Night Temperatures During Cotton's Early Reproductive Stage Affect Leaf Physiology and Flower Bud Carbohydrate Content Decreasing Flower Bud Retention

“…Snider et al. (, ) observed lower carbohydrate concentrations in heat‐stressed cotton pistils and reported that a limited sucrose supply might disrupt their development and result in reproductive unit abortion, but they indicated that carbohydrate translocation from the subtending leaf to the flower was not impeded because carbohydrate content of heat‐stressed cotton pistils was similar to those of the control regardless the decreases observed in leaf carbohydrate concentrations. In support of that observation, Zhao et al.…”

“…As mentioned above, heat stress results in disruptions in carbon assimilation functions decreasing the availability of carbohydrates and especially sucrose to the reproductive units (Aloni et al 1991, Qin et al 2008. Snider et al (2009Snider et al ( , 2011 observed lower carbohydrate concentrations in heat-stressed cotton pistils and reported that a limited sucrose supply might disrupt their development and result in reproductive unit abortion, but they indicated that carbohydrate translocation from the subtending leaf to the flower was not impeded because carbohydrate content of heat-stressed cotton pistils was similar to those of the control regardless the decreases observed in leaf carbohydrate concentrations. In support of that observation, Zhao et al (2005) reported that decreases in non-structural carbohydrate concentrations of heat-stressed cotton flower buds and young bolls, but not decreases in leaf carbohydrate concentrations, were highly correlated with fruit abscission.…”

High Temperature and the Ethylene Antagonist 1-Methylcyclopropene Alter Ethylene Evolution Patterns, Antioxidant Responses, and Boll Growth in <i>Gossypium hirsutum</i>

“…Snider et al [6,8] have also reported increases in GR activity in G. hirsutum pistils exposed to high temperature conditions. Importantly, GR activity increased in young bolls (Figure 3) exposed to high temperature, but this increase does not appear to be associated with increased ethylene production, since ethylene production was decreased by high temperature (Figure 2).…”