Leigh Andrea, Close John D, Ball Marilyn C, Siebke Katharina, Nicotra Adrienne B
School of Botany and Zoology, The Australian National University, Canberra, ACT 0200, Australia.
Department of Physics and the Australian Centre for Quantum Atom Optics, The Australian National University, Canberra, ACT 0200, Australia.
Funct Plant Biol. 2006 May;33(5):515-519. doi: 10.1071/FP05300.
Despite the obvious benefits of using thermography under field conditions, most infrared studies at the leaf level are generally conducted in the laboratory. One reason for this bias is that accuracy can potentially be compromised in sunlight because reflected radiation from the leaf might affect the calculation of the temperature measurement. We have developed a method for measuring leaf temperature in sunlight by using thermal imagery to generate cooling curves from which the time constant for cooling, τ, can be calculated. The original temperature of the sunlit leaf may be determined by extrapolating backwards in time. In the absence of specular reflection, there is close agreement between the extrapolated sunlit temperature and the sunlit temperature recorded by the camera. However, when reflected radiation is high, the difference between the initial (incorrect) temperature determined from the sunlit image and the temperature extrapolated from the cooling curve can be > 2°C. Notably, our results demonstrate a close agreement between the extrapolated sunlit temperature and the temperature of the leaf approximately 1 s after being shaded, suggesting that this shaded image provides a good estimate of the original sunlit temperature. Thus, our technique provides two means for measuring leaf surface temperature in sunlight.
尽管在野外条件下使用热成像技术有明显的好处，但大多数叶片水平的红外研究通常是在实验室进行的。这种偏差的一个原因是，在阳光下准确性可能会受到影响，因为叶片的反射辐射可能会影响温度测量的计算。我们开发了一种在阳光下测量叶片温度的方法，通过使用热成像生成冷却曲线，从中可以计算出冷却时间常数τ。通过向后外推时间可以确定阳光照射下叶片的初始温度。在没有镜面反射的情况下，外推的阳光照射温度与相机记录的阳光照射温度之间有密切的一致性。然而，当反射辐射较高时，从阳光照射图像确定的初始（错误）温度与从冷却曲线外推的温度之间的差异可能大于2°C。值得注意的是，我们的结果表明，外推的阳光照射温度与叶片在被遮蔽后约1秒的温度之间有密切的一致性，这表明这个被遮蔽的图像可以很好地估计原始的阳光照射温度。因此，我们的技术提供了两种在阳光下测量叶片表面温度的方法。
