Populus deltoides is a fast-growing woody species possessing plethora of industrial applications. This species evolutionarily developed unisexual male and female catkin inflorescence on separate trees. Flowering usually occurs during early spring before the development of foliage, where buds appear near axils or at the extending shoots. In 2019, surveys were undertaken to study the flowering pattern of P. deltoides in the states of Punjab, Haryana, Uttar Pradesh and Uttarakhand in northern India. Interestingly, an anomalous flowering behaviour (appearance of off-season male catkins during autumn, i.e. October) was observed in a plantation trial at Kapurthala, Punjab. The male catkins were 2.7–3.1 ± 0.07 cm long and 0.3–0.5 ± 0.03 cm wide, which is significant for flowering and liberation of pollen grains. Preliminary results suggested that climatic factors, such as episodes of high or low temperature and the precipitation variation forcing the tree species to behave differently. Unearthing the climate-driven off-season flowering in other tree species alluded the stimulation of phytohormones, such as gibberellic and salicylic acid concentrations influencing the flowering time, therefore, needs further investigation in case of P. deltoides. Overall, this work provides early clues of changing climatic scenario altering the flowering pattern of a tropical forestry tree species.

中文翻译：

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印度杨树淡季开花的首次记录：气候变化指标范式

Populus deltoides 是一种快速生长的木本物种，具有大量的工业应用。该物种在不同的树上进化出单性雄性和雌性柔荑花序。开花通常发生在早春叶子发育之前，芽出现在腋下或延伸的枝条处。2019 年，在印度北部旁遮普邦、哈里亚纳邦、北方邦和北阿坎德邦进行了调查，以研究三角梅的开花模式。有趣的是，在旁遮普省 Kapurthala 的种植园试验中观察到异常开花行为（秋季即 10 月出现淡季雄性柳絮）。雄性柳絮长2.7-3.1±0.07厘米，宽0.3-0.5±0.03厘米，对开花和花粉粒的释放具有重要意义。初步结果表明，气候因素，如高温或低温事件和降水变化迫使树种表现不同。在其他树种中发现气候驱动的淡季开花暗示了植物激素的刺激，例如影响开花时间的赤霉酸和水杨酸浓度，因此，需要进一步调查 P. deltoides 的情况。总体而言，这项工作提供了气候变化改变热带林业树种开花模式的早期线索。如赤霉素和水杨酸浓度影响开花时间，因此，需要进一步研究 P. deltoides 的情况。总体而言，这项工作提供了气候变化改变热带林业树种开花模式的早期线索。如赤霉素和水杨酸浓度影响开花时间，因此，需要进一步研究 P. deltoides 的情况。总体而言，这项工作提供了气候变化改变热带林业树种开花模式的早期线索。