Effects of free-air CO2 enrichment on heat-induced sterility and pollination in rice

• Main Authors: Kazuhiro Kobayasi, Mohammad Jawid Eydi, Hidemitsu Sakai, Takeshi Tokida, Hirofumi Nakamura, Yasuhiro Usui, Mayumi Yoshimoto, Toshihiro Hasegawa
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2019-07-01
• Series: Plant Production Science
• Subjects: air temperature; anther; elevated co2; free-air co2 enrichment; heat-induced sterility; pollination; rice
• Online Access: http://dx.doi.org/10.1080/1343943X.2018.1563496

Global climate changes may cause heat-induced sterility in rice, threatening the global production of this important crop. Although little is currently known about the combined effects of the concentration of atmospheric CO2 ([CO2]) and temperature on heat-induced sterility, elevated [CO2] (E-[CO2]) will likely increase the panicle temperature and thereby exacerbate heat-induced sterility, but this was not tested in open fields. Therefore, we investigated the effect of E-[CO2] on heat-induced sterility and sterility-related traits in rice by increasing E-[CO2] by approximately 200 μmol mol−1 above ambient levels using a free-air CO2 enrichment (FACE) facility for six growing seasons with variable growing season temperatures. The percentage fertility was not significantly correlated with the air temperature (Ta) between 09:00 and 12:00 on each flowering day, but it did significantly vary among the years, with 2011 experiencing cool temperatures resulting in chilling-induced mild sterility. When data from 2011 were removed, there was a significant negative correlation between fertility and Ta between 09:00 and 12:00 on each flowering day under E-[CO2], whereas no such effect was seen under ambient [CO2]. E-[CO2] also significantly reduced the number of pollen grains deposited on the stigma by 10%, but it slightly increased the anther length by 1.3%, indicating that it had both negative and positive effects on heat-induced sterility. These findings suggest that E-[CO2] affects many traits related to heat-induced sterility and may sometimes exacerbate sterility by reducing pollen grain deposition. Abbreviations: A-[CO2]: ambient CO2; [CO2]: the concentration of carbon dioxide; E-[CO2]: elevated [CO2]; FACE: free-air CO2 enrichment; Ta: air temperature