Deb Debal, Dutta Sreejata, Nauri Mahendra
Centre for Interdisciplinary Studies, Kolkata, 700001, India.
Department of Biostatistics and Data Science, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
Biol Futur. 2025 Aug 12. doi: 10.1007/s42977-025-00277-z.
Records of sunlight intensity at anthesis of 388 rice landraces (with 32 replicated populations), flowering in the short-day season of 2022, reveal that under cloudy condition, the rice florets tend to open later, or the sunrise-to-anthesis duration (SAD) is longer when rice florets open than at sunny period. This difference in the length of SAD was statistically highly significant (p < 0.0001), confirmed by a two-sample permutation test with 10,000 iterations. This finding corroborates our general observation previously reported from a larger set of 1114 landraces (including the 388 landraces examined in this study). However, the intensity of sunlight at the flower opening time (FOT) may not remain uniformly sunny (high illuminance) or cloudy (low illuminance, < 40,000 lx) until the flower closing time (FCT). To understand the effect of uniformly low sunlight intensity, we subsequently recorded solar illuminance at FOT of 33 landrace populations (including 8 repeats). Half of each population was kept under artificial shade, compared to the other half exposed to sunlight. This experiment revealed that low illuminance, mimicking overcast days, significantly (p < 0.02) delays FOT and lengthens SAD, corroborating the pattern detected in our earlier findings. Permutation test with 10,000 iterations decisively confirms (p < 0.0001) the prolongation of SAD under shade and cloudy conditions. Experimental shading has an indeterminate effect on flower exposure duration (FED) of the same landraces. We surmise that the delayed FOT during natural cloudy period is an adaptation in rice plants in anticipation of rain, for protection of the pollen from rainwash.
对388个水稻地方品种（有32个重复群体）在2022年短日照季节开花期的阳光强度记录显示，在阴天条件下，水稻小花往往开放较晚，或者水稻小花开放时从日出到开花的持续时间（SAD）比晴天时长。SAD长度的这种差异在统计学上具有高度显著性（p < 0.0001），通过10000次迭代的双样本置换检验得到证实。这一发现证实了我们之前从1114个更大样本量的地方品种（包括本研究中检测的388个地方品种）中得出的总体观察结果。然而，直到花朵闭合时间（FCT），开花时（FOT）的阳光强度可能不会一直保持晴天（高照度）或阴天（低照度，<40000勒克斯）。为了了解均匀低阳光强度的影响，我们随后记录了33个地方品种群体（包括8次重复）开花时的太阳照度。每个群体的一半置于人工遮荫下，另一半暴露在阳光下。该实验表明，模拟阴天的低照度显著（p < 0.02）延迟了开花时间并延长了SAD，证实了我们早期研究结果中检测到的模式。10000次迭代的置换检验决定性地证实（p < 0.0001）在遮荫和阴天条件下SAD会延长。实验性遮荫对同一地方品种的花朵暴露持续时间（FED）有不确定的影响。我们推测，在自然阴天期间开花时间延迟是水稻植株为了防雨而做出的一种适应，以保护花粉不被雨水冲走。
