Pollen, ovules, and pollination in pea: Success, failure, and resilience in heat

Abstract

Field pea (Pisum sativum), a major grain legume crop, is autogamous and adapted to temperate climates. The objectives of this study were to investigate effects of high temperature stress on stamen chemical composition, anther dehiscence, pollen viability, pollen interactions with pistil and ovules, and ovule growth and viability. Two cultivars ("CDC Golden" and "CDC Sage") were exposed to 24/18°C (day/night) continually or to 35/18°C for 4 or 7 days. Heat stress altered stamen chemical composition, with lipid composition of "CDC Sage" being more stable compared with "CDC Golden." Heat stress reduced pollen viability and the proportion of ovules that received a pollen tube. After 4 days at 35°C, pollen viability in flower buds decreased in "CDC Golden," but not in "CDC Sage." After 7 days, partial to full failure of anthers to dehisce resulted in subnormal pollen loads on stigmas. Although growth (ovule size) of fertilized ovules was stimulated by 35°C, heat stress tended to decrease ovule viability. Pollen appears susceptible to stress, but not many grains are needed for successful fertilization. Ovule fertilization and embryos are less susceptible to heat, but further research is warranted to link the exact degree of resilience to stress intensity.

Reproductive development response to high daytime temperature in field pea

“…The same phenomenon was observed in sorghum, and thus, pollen was more susceptible to heat stress compared to pistil since pollen was more sensitive to oxidative damage—increasing the ROS accumulation and decreasing antioxidant enzyme activity (Djanaguiraman et al., ). Our previous research also indicated that male floral organs in field pea were more sensitive to heat stress compared to female floral counterparts, because ovule viability was affected by heat stress at p < 0.10 not at p < 0.05 like pollen (Jiang, et al., ).…”

“…However, our recent growth chamber studies showed that "CDC Sage" had more stable pollen surface and anther lipid composition compared to "CDC Golden," and "CDC Sage" had also a greater in vitro pollen germination percentage and pollen viability (Jiang et al, 2015;Jiang, et al, 2019).…”

“…These cultivars are moderately indeterminate spring‐habit types, and they mature in western Canada in <95 days. Therefore, it was hypothesized that “CDC Golden” would be more heat‐tolerant compared to “CDC Sage.” However, our recent growth chamber studies showed that “CDC Sage” had more stable pollen surface and anther lipid composition compared to “CDC Golden,” and “CDC Sage” had also a greater in vitro pollen germination percentage and pollen viability (Jiang et al., ; Jiang, et al., ).…”

“…High temperature stress negatively affects pollen development and seed set. Heat stress reduced pollen viability, in vitro pollen germination and pollen tube length in field pea (Jiang, 2016;Jiang, Bueckert, Warkentin, & Davis, 2018;Jiang et al, 2015;Jiang, et al, 2019). Pollen grains produced normal exine but no or little cytoplasm in barley (Hordeum vulgare) when exposed to 30/25°C day/night temperatures for 5 days at the early differentiation stage of the panicle, whereas the same high temperature regime led to the development of short anthers without pollen grains during heat exposure at the pre-meiotic stage of pollen mother cells (Sakata, Takahashi, Nishiyama, & Higashitani, 2000).…”

Legumes—The art and science of environmentally sustainable agriculture

“…Understanding how heat stress influences reproductive organs is critical to improving grain legume yields in future climates. The study reported by Jiang et al () shows that heat stress exposure in pea leads to a greater inhibition of pollen development and viability than of ovules. A heat tolerant pea genotype was found to exhibit a more stable lipid composition in the stamens.…”