Equivalent hours of maximum net photosynthesis

Abstract

A method is described that defines physiological growing seasons for crop plants with a unit of accumulation called an equivalent hour of maximum net photosynthesis or EHMNP. This unit is the net photosynthetic response of a plant for one hour at optimum conditions of light and temperature where hours with partial responses can add together to make full hours. Calculation of EHMNP values involves the response of net photosynthesis to simulated daylight temperatures, to sunlight intensity in accordance with sun zenith angles, and it includes subtraction of nocturnal respiration losses. Annual marches of monthly EHMNP totals delineate the physiological growing seasons which are distinctive to various agro-climatic environments. Growing seasons of specific crops can be analyzed by the way they fit into the potential physiological growing seasons defined by EHMNP accumulations.