植物生长节律描绘了植物的生物物理和生理行为，受植物内在生物钟和外源环境共同调控。探索植物生长节律对于了解植物对环境变化的适应策略十分重要。相比于生理节律的研究，指示植物结构节律的研究鲜有报道。近年来，地面激光雷达(TLS)为植物结构动态研究提供了新途径，发现了如夜间“树木睡觉”等新的科学现象。这些尝试发现不同树种间不一致的节律，证明了树木睡眠问题的复杂性，也启发了关于作物是否会有“夜间睡觉”等结构节律问题的思考。

近日，Plant Phenomics在线发表了南京农业大学前沿交叉研究院作物表型组学交叉研究中心金时超课题组题为Exploring Seasonal and Circadian Rhythms in Structural Traits of Field Maize from LiDAR Time Series的研究论文。

该研究旨在量化玉米单株和叶片结构性状的季节性和昼夜节律，包括正常生长和冷害环境胁迫两种田间环境。采用国内首套自主研发的高通量激光雷达表型平台(Crop3D, Fig.1)获取了玉米四个关键生长期的点云数据，用于研究季节性节律。同时，获取了每2小时频率的点云数据分析昼夜节律(Fig.1)。具体问题包括：(1)TLS能否量化田间自然状况下作物结构表型的季节性节律？(2)能否量化正常生长和冷害条件下的作物结构表型的昼夜节律？(3)正常和冷害条件下环境因素与结构表型昼夜节律的潜在关系？

研究结果表明TLS可以量化单株和叶片水平作物结构表型的季节性和的昼夜节律。(1)叶倾角在拔节期到喇叭口期明显减小，叶方位角在拔节期后保持稳定(Fig.4)。(2)一些单株结构表型的节律（例如，方位角和投影叶面积）与叶片结构表型节律一致（Fig.3和Fig.4）。(3)部分性状（例如，投影叶面积）的昼夜节律在正常和冷害条件下表现不一致（Fig.6和Fig.8）。(4)环境因素与叶片昼夜节律的相关性在冷害情况下高于正常环境。温度是最重要的因素，与除叶方位角外的所有叶性状显著相关（Table.2和Table.3）。这项研究拓展了时间序列激光雷达在田间作物节律领域的新方向。

Figure 1: Study area and LiDAR data collection.

Figure 3: Seasonal rhythms of plant structural traits, including (a)Hmax, (b)Hmean, (c)H99, (d) crown size, (e) azimuth, (f) PLA, (g) volume, (h) PAI, and (i) 3DPI.

Figure 4: Seasonal rhythms of leaf structural traits, including (a) leaf length, (b) max. leaf width, (c) mean leaf width, (d) leaf height, (e) leaf area, (f) PLL, (g) PLA, (h) leaf inclination, and (i) leaf azimuth.

Figure 6: Circadian rhythms in structural traits of maize at the leaf level under standard conditions, including (a) leaf length, (b) max. leaf width, (c) mean leaf width, (d) leaf height, (e) leaf area, (f) PLL, (g) PLA, (h) leaf inclination, and (i) leaf azimuth.

Figure 8: Circadian rhythms in structural traits of maize at the leaf level under cold stress, including (a) leaf length, (b) maximum leaf width, (c) mean leaf width, (d) leaf height, (e) leaf area, (f) PLL, (g) PLA, (h) leaf inclination, and (i) leaf azimuth, at leaf level under cold stress.

Table2:The relationships denoted by the Pearson correlation coefficient and p value between environmental factors (photosynthetically active radiation (PAR), temperature (T), and relative humidity (RH)) and circadian rhythms in structural traits at the plant level under standard and cold stress conditions.

Table3:The relationship denoted by the Pearson correlation coefficient and p value between environmental factors (photosynthetically active radiation (PAR), temperature (T), and relative humidity (RH)) and circadian rhythm in structural traits at leaf level under standard and cold stress growth.

本研究得到了中科院植物所苏艳军研究员、刘玲莉研究员；南京大学张永光教授；密西西比州立大学马勤教授；南京农业大学丁艳锋教授；法国农科院Fred Baret教授和北京大学郭庆华教授等共同作者的支持。研究得到了中科院先导专项和江苏省科技厅创新能力建设项目（植物表型组学研究科学中心）等项目的资助，特此感谢。

作者简介

https://spj.sciencemag.org/journals/plantphenomics/2021/9895241/

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