Abstract
We tested whether exposing rice plants to abiotic stress (salt or shade) during vegetative growth affects the chilling tolerance of reproductive organs, which is one of the most important traits for rice growing in a cool climate; we used two rice cultivars with different tolerance in two growing seasons. We divided the vegetative growth into three phases to clarify the most sensitive period: 7–22 days after transplanting (DAT), 23–38 DAT and 39–54 DAT. Chilling tolerance of the pre-stressed plants was based on the male sterility induced by low temperatures. Shade and salt stress during all three vegetative growth phases significantly reduced stomatal conductance. Shade decreased the specific leaf weight and the leaf sugar and starch contents, but salt had no significant effect, despite causing leaf damage. Low temperatures during the reproductive stage induced spikelet sterility in all plants, but the magnitude was greater in the salt- and shade-stressed plants of both cultivars, especially those stressed late during vegetative growth. The increased spikelet sterility caused by chilling was closely related to the reduction of the total spikelet number per panicle. This is the first study to show that salt and low light stress during vegetative growth increased the susceptibility of rice plants to chilling damage during panicle development.
Highlights
Rice (Oryza sativa L.), which originated in a tropical environment, is sensitive to suboptimal temperatures, especially during the reproductive stage, when temperatures lower than 20 °C can induce male sterility, leading to severe yield losses (Matsushima et al, 1964; Shimono et al, 2002)
We found that the episode by low temperature at vegetative stage decreased the chilling tolerance (Shimono et al, 2007; Suzuki et al, 2015)
It is visually difficult to identify the differences in plant morphology between shaded and unshaded plants at this stage when is the timing of start of chilling tolerance test during the reproductive stage (Supplemental Figure S3)
Summary
Rice (Oryza sativa L.), which originated in a tropical environment, is sensitive to suboptimal temperatures, especially during the reproductive stage, when temperatures lower than 20 °C can induce male sterility, leading to severe yield losses (Matsushima et al, 1964; Shimono et al, 2002). We found that the episode by low temperature at vegetative stage decreased the chilling tolerance (male sterility) (Shimono et al, 2007; Suzuki et al, 2015) This phenomena was commonly observed over nine rice cultivars at different conditions in a greenhouse (Shimono et al, 2007), in the field (Abe et al, 2013; Kanda et al, 2012; Shimono & Kanda, 2008; Shimono et al, 2011; Shimono et al, 2012), and under fully controlled-environment conditions (Matsumura et al, 2012; Suzuki et al, 2015). We found no studies that investigated whether the phenomena could be triggered by environmental cues other than temperature during vegetative growth
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