Absorption of visible light by floral anthocyanins increases flower temperatures: implications for a warmer world

With rising global temperatures, understanding the mechanisms that influence plant thermal energy balance are critical to forecasting plant and pollinator responses. Flower temperatures impact visitation by insect pollinators, and several temperature-sensitive processes central to plant reproduction. Anthocyanin pigments absorb strongly in visible and ultraviolet wavebands, but clear support for a warming effect of pigments on flowers has remained elusive. We used infrared imaging to measure petal temperatures of horticultural varieties of plants differing in floral anthocyanin content. Excised sets of flowers were mounted perpendicularly to the sun, and exposed to direct ambient sunlight filtered either through Aclar (UV-transparent) or Courtguard (UV-opaque) under low-wind (< 1 m s-1) conditions. Petal temperatures were measured after one minute, and treatment order alternated between replicates. Results showed that pigmented flowers were consistently significantly warmer than white conspecifics (2.9°C warmer on average for lightly-pigmented varieties, 5.3°C warmer for darkly-pigmented). Most species showed no significant difference in petal temperatures under UV inclusion versus exclusion, indicating most warming by anthocyanins can be attributed to absorption of visible light. UV-enhanced warming was observed in some species, which could be due to the presence of side groups that enhance UV-absorption by the anthocyanin molecules. However, these differences were slight (always

随着全球温度的上升，理解影响植物热能平衡的机制对于预测植物和授粉者的反应至关重要。花朵的温度影响昆虫授粉者的访问以及与植物繁殖密切相关的一系列温度敏感过程。花青素色素在可见光和紫外波段内吸收强烈，但关于色素对花朵温度升高的影响是否存在的支持仍显不足。本研究利用红外成像技术测量了不同花卉花青素含量的园艺品种花瓣温度。从花朵中取出的样本以垂直于太阳的方向固定，在低风速（<1米/秒）的条件下，通过Aclar（紫外线透明）或Courtguard（紫外线不透明）过滤直接环境光照。测量花瓣温度后，处理顺序在重复之间交替。结果显示，着色花朵的平均温度显著高于白色同种植物（轻度着色品种平均高2.9°C，重度着色品种高5.3°C）。大多数物种在紫外线包含与排除条件下花瓣温度没有显著差异，表明大多数由花青素引起的升温可归因于对可见光的吸收。在某些物种中观察到紫外线增强的升温，这可能是由于存在增强花青素分子紫外线吸收的侧链。然而，这些差异微乎其微（始终）