Abstract Plants rely on spectral cues present in their surroundings, generated by the constantly changing light environment, to guide their growth and reproduction. Photoreceptors mediate the capture of information by plants from the light environment over a wide range of wavelengths, but despite extensive evidence that plants respond to various light cues, only fragmentary data have been published showing patterns of diurnal, seasonal and geographical variation in the spectral composition of daylight. To illustrate patterns in spectral photon ratios, we measured time series of irradiance spectra at two distinct geographical and climatological locations, Helsinki, Finland and Gual Pahari, India. We investigated the drivers behind variation of the spectral photon ratios measured at these two locations, based on the analysis of over 400 000 recorded spectra. Differences in spectral irradiance were explained by different atmospheric factors identified through multiple regression model analysis and comparison to spectral irradiance at ground level simulated with a radiative transfer model. Local seasonal and diurnal changes in spectral photon ratios were related to solar elevation angle, atmospheric water-vapour content and total ozone column thickness and deviated from their long-term averages to an extent likely to affect plant photobiology. We suggest that future studies should investigate possible effects of varying photon ratios on terrestrial plants. Solar elevation angle especially affects the patterns of B:G and B:R ratios. Water vapour has a large effect on the R:FR photon ratio and modelled climate scenarios predict that increasing global temperatures will result in increased atmospheric water vapour. The development of proxy models, utilising available data from weather and climate models, for relevant photon ratios as a function of solar elevation angle and atmospheric factors would facilitate the interpretation of results from past, present and future field studies of plants and vegetation.

中文翻译：

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受大气因素影响的阳光光谱组成模式和具有生物学意义的光谱光子比率

摘要 植物依靠周围环境中不断变化的光环境产生的光谱线索来指导它们的生长和繁殖。光感受器介导植物从光环境中在很宽的波长范围内捕获信息，但尽管有大量证据表明植物对各种光线索有反应，但仅发表了零碎数据，显示光谱组成中的昼夜、季节和地理变化模式的白天。为了说明光谱光子比率的模式，我们在芬兰赫尔辛基和印度瓜尔帕哈里两个不同的地理和气候位置测量了辐照光谱的时间序列。我们研究了在这两个位置测量的光谱光子比变化背后的驱动因素，基于对超过 400 000 个记录光谱的分析。光谱辐照度的差异可以通过多元回归模型分析确定的不同大气因素来解释，并与用辐射传输模型模拟的地面光谱辐照度进行比较。光谱光子比的局部季节性和昼夜变化与太阳高度角、大气水汽含量和总臭氧柱厚度有关，并且偏离其长期平均值到可能影响植物光生物学的程度。我们建议未来的研究应该调查不同光子比率对陆生植物的可能影响。太阳高度角尤其影响 B:G 和 B:R 比率的模式。水蒸气对 R 有很大影响：FR 光子比和模拟气候情景预测，全球气温升高将导致大气水蒸气增加。利用天气和气候模型的可用数据，开发作为太阳高度角和大气因素函数的相关光子比率的代理模型将有助于解释过去、现在和未来植物和植被实地研究的结果。