Harrap Michael J M, Rands Sean A
University of Bristol, Life Sciences Building, Tyndall Ave, Bristol, BS8 1TQ, UK.
Plant Methods. 2021 Feb 25;17(1):23. doi: 10.1186/s13007-021-00721-w.
Floral temperature has important consequences for plant biology, and accurate temperature measurements are therefore important to plant research. Thermography, also referred to as thermal imaging, is beginning to be used more frequently to measure and visualize floral temperature. Accurate thermographic measurements require information about the object's emissivity (its capacity to emit thermal radiation with temperature), to obtain accurate temperature readings. However, there are currently no published estimates of floral emissivity available. This is most likely to be due to flowers being unsuitable for the most common protocols for emissivity estimation. Instead, researchers have used emissivity estimates collected on vegetative plant tissue when conducting floral thermography, assuming these tissues to have the same emissivity. As floral tissue differs from vegetative tissue, it is unclear how appropriate and accurate these vegetative tissue emissivity estimates are when they are applied to floral tissue.
We collect floral emissivity estimates using two protocols, using a thermocouple and a water bath, providing a guide for making estimates of floral emissivity that can be carried out without needing specialist equipment (apart from the thermal camera). Both protocols involve measuring the thermal infrared radiation from flowers of a known temperature, providing the required information for emissivity estimation. Floral temperature is known within these protocols using either a thermocouple, or by heating the flowers within a water bath. Emissivity estimates indicate floral emissivity is high, near 1, at least across petals. While the two protocols generally indicated the same trends, the water bath protocol gave more realistic and less variable estimates. While some variation with flower species and location on the flower is observed in emissivity estimates, these are generally small or can be explained as resulting from artefacts of these protocols, relating to thermocouple or water surface contact quality.
Floral emissivity appears to be high, and seems quite consistent across most flowers and between species, at least across petals. A value near 1, for example 0.98, is recommended for accurate thermographic measurements of floral temperature. This suggests that the similarly high values based on vegetation emissivity estimates used by previous researchers were appropriate.
花朵温度对植物生物学具有重要影响，因此准确的温度测量对植物研究至关重要。热成像技术，也被称为热成像，开始越来越频繁地用于测量和可视化花朵温度。准确的热成像测量需要有关物体发射率（其随温度发射热辐射的能力）的信息，以获得准确的温度读数。然而，目前尚无已发表的花朵发射率估计值。这很可能是因为花朵不适合用于最常见的发射率估计协议。相反，研究人员在进行花朵热成像时使用了在植物营养组织上收集的发射率估计值，假设这些组织具有相同的发射率。由于花朵组织与营养组织不同，尚不清楚将这些营养组织发射率估计值应用于花朵组织时的适用性和准确性如何。
我们使用两种协议收集花朵发射率估计值，一种使用热电偶，另一种使用水浴，提供了一种无需专门设备（除热成像相机外）即可进行花朵发射率估计的指南。两种协议都涉及测量来自已知温度花朵的热红外辐射，提供发射率估计所需的信息。在这些协议中，使用热电偶或通过在水浴中加热花朵来确定花朵温度。发射率估计表明花朵发射率很高，至少在花瓣上接近1。虽然两种协议通常显示相同的趋势，但水浴协议给出的估计值更现实且变化较小。虽然在发射率估计中观察到一些因花的种类和花朵上的位置而产生的变化，但这些通常很小，或者可以解释为这些协议的人为因素导致的，与热电偶或水面接触质量有关。
花朵发射率似乎很高，并且在大多数花朵之间以及不同物种之间似乎相当一致，至少在花瓣上是这样。建议使用接近1的值，例如0.98，用于花朵温度的准确热成像测量。这表明先前研究人员基于植被发射率估计使用的类似高值是合适的。
