Abstract
ABSTRACTGlobal 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
Highlights
According to the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013), the atmospheric concentrations of greenhouse gases have increased since 1750 as a result of human activities, with the concentration of carbon dioxide ([CO2]) in 2011 (391 μmol mol−1) exceeding preindustrial levels by approximately 40%
We found that an increased Ta between 09:00 and 12:00 on each flowering day slightly decreased the percentage fertility of rice plants under E-[CO2] but had no effect under A[CO2] (Figure 1)
Previous experiments conducted under enclosed conditions have shown that heatinduced sterility is often exacerbated by E-[CO2] (Chaturvedi et al, 2017; Kim et al, 1996; Matsui et al, 1997), which increases the panicle temperature by inducing leaf stomatal closure and reducing leaf stomatal conductance
Summary
According to the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2013), the atmospheric concentrations of greenhouse gases have increased since 1750 as a result of human activities, with the concentration of carbon dioxide ([CO2]) in 2011 (391 μmol mol−1) exceeding preindustrial levels by approximately 40% This has led to a combined global average increase in land and ocean surface temperatures of 0.85°C (IPCC, 2013), which threatens the production of many crops, including rice, an important staple food in Asia and Africa. In a growth chamber experiment, Kobayasi et al (2011) demonstrated that the relative contribution of anther indehiscence and the basal dehiscence length to pollination (percentage of sufficiently pollinated florets) changed according to Ta, with the percentage of dehisced anthers becoming more important with increasing Ta
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