Photosynthetic and transpiration responses to light, CO2, temperature, and leaf senescence in garlic: Analysis and modeling

Abstract

Characterization of leaf physiology is an important step for understanding the ecophysiology of a crop as well as for developing a process-based crop simulation model. We determined photosynthetic and transpiration responses to photosynthetic photon flux (PPF), carbon dioxide concentrations, and temperature, and parameterized a coupled leaf gas-exchange model for hardneck garlic (Allium sativum). The parameterized model performed with high accuracy and precision in predicting photosynthetic responses [r2 = 0.95, bias = 1.7 jumol m 2s 1, root mean square error (RMSE) = 2.4 jumol m 2s 1] when tested against independent data that were not used for model calibration. The model performance for transpiration rates was less satisfactory (r2 = 0.49, bias = -0.14 mmolm 2s 1, RMSE = 0.94 mmolm 2s 1). In addition, we characterized the relationships among chlorophyll meter readings, leaf photosynthetic capacity (Amax), and leaf nitrogen content in garlic leaves. The chlorophyll meter readings were a reasonable indicator of bothAmax (r2 = 0.61) and leaf nitrogen (N) status (r2 = 0.51) for garlic leaves we studied. The garlic leaf gas-exchange model developed in this study can serve as a key component in ecophysiological crop models for garlic. Similarly, the quantitative relationship identified between chlorophyll meter readings and Amax in this study can provide useful information for non-destructively assessing leaf photosynthetic capacity in garlic.