Apland Jennifer S, Riddle Katherine E, Koski Matthew H
Department of Biological Sciences, Clemson University, Clemson, SC, USA.
Michigan State University Herbarium, East Lansing, MI, USA.
Am J Bot. 2025 Jul 14:e70070. doi: 10.1002/ajb2.70070.
The floral thermal microenvironment impacts plant reproduction through its effects on gametophyte performance and plant-pollinator interactions. Color and shape are axes of floral variation that may mediate floral temperature because they affect the absorption and reflection of solar radiation, but their interactive effects are unclear. Additionally, near infrared (NIR) reflectance is important for organismal temperature, but the contribution of petal NIR reflectance to floral temperature has not been assessed.
In a subalpine meadow during peak solar radiation, we continuously tracked temperature of the floral microenvironment and air temperature outside of flowers for species that differed in floral shape and dominant floral color (yellow vs. anthocyanic [pink, blue, red]). We related shape, color, surface area, and UV-NIR petal reflectance to floral temperature metrics.
Flowers with exposed reproductive structures ("open") warmed more than those with concealed reproductive structures ("closed"), and this effect was strongest for yellow flowers. Closed flowers were more thermally stable than open flowers regardless of color. Open flowers with larger surface area also warmed more. NIR reflectance (700-900 nm) was strongly correlated with visible reflectance (500-700 nm), so its effect on floral temperature could not be isolated. However, closed flowers with stronger reflectance from 500 to 900 nm were cooler and more thermally stable.
Our results show that floral color, reflectance, and shape interact to influence the temperature of the floral microenvironment of our focal taxa. They provide a predictive framework for how floral traits may change across space and time in response to temperature variation.
花的热微环境通过对配子体性能和植物 - 传粉者相互作用的影响来影响植物繁殖。颜色和形状是花变异的两个方面，可能会调节花的温度，因为它们会影响太阳辐射的吸收和反射，但其交互作用尚不清楚。此外，近红外（NIR）反射率对生物体温度很重要，但花瓣近红外反射率对花温度的贡献尚未得到评估。
在太阳辐射峰值期间的亚高山草甸中，我们持续跟踪了花的微环境温度以及花朵外部的气温，这些花朵在花的形状和主要花色（黄色与花色苷类[粉色、蓝色、红色]）上存在差异。我们将形状、颜色、表面积以及紫外 - 近红外花瓣反射率与花温度指标相关联。
具有外露生殖结构（“开放”）的花朵比具有隐蔽生殖结构（“闭合”）的花朵升温更多，这种效应在黄色花朵中最为明显。无论颜色如何，闭合花朵的热稳定性都比开放花朵更高。表面积较大的开放花朵升温也更多。近红外反射率（700 - 900纳米）与可见光反射率（500 - 700纳米）密切相关，因此其对花温度的影响无法单独分离出来。然而，在500至900纳米范围内反射率较强的闭合花朵温度较低且热稳定性更高。
我们的结果表明，花的颜色、反射率和形状相互作用，影响了我们所关注类群的花微环境温度。它们为花的性状如何随温度变化在空间和时间上发生改变提供了一个预测框架。
