A simple new method to determine leaf specific heat capacity.

BACKGROUND

Quantifying plant transpiration via thermal imaging is desirable for applications in agriculture, plant breeding, and plant science. However, thermal imaging under natural non-steady state conditions is currently limited by the difficulty of quantifying thermal properties of leaves, especially specific heat capacity (C). Existing literature offers only rough estimates of C and lacks simple and accurate methods to determine it.

RESULTS

We developed a non-invasive method to quantify k (the product of leaf thickness (lt), leaf density(ρ), and C), by fitting a leaf energy balance model to a leaf temperature (T) transient during and after a ~ 10 s light pulse. C was then estimated by dividing k by lt*ρ. Using this method, we quantified C for 13 horticultural and tropical plant species, and explored the relationship between C and leaf water content, specific leaf area and T response rate during the light pulse. Values of C ranged between 3200-4000 J kg K, and were positively correlated with leaf water content. In species with very thick leaves, such as Phalaenopsis amabilis, we found leaf thickness to be a major factor in the temperature response to a short light pulse.

CONCLUSIONS

Our method allows for easy determination of leaf C of different species, and may help pave the way to apply more accurate thermal imaging under natural non-steady state conditions.