The combined effect of cold and light intensity stress on some morphological and physiological parameters in two soybean (Glycine max L.) cultivars

Abstract

In order to evaluate the response of two soybean cultivars (032 and BP) to cold stress [control (28°C) and cold stress (5°C)] at two light intensity levels [normal light (8000 lux) or low light (2000 lux) intensity], an experiment was done in a factorial arrangement based on completely randomized design with three replicates under greenhouse conditions. The results clearly showed that leaf number and chlorophyll a and ab contents in soybean seedlings have a tendency to decrease (31, 17 and 14 %, respectively) by cold stress while stem diameter markedly increased (up to 15) as compared to those grown under control conditions. Cold stress reduced nodes number, plant height and chlorophyll content (SPAD value) in two light intensities, however, this effect is more noticeable at low light intensity for nod numbers (31%) and plant height (56%) and at high light intensity for SPAD value (21%). Cold stress also significantly suppressed plant height in both cultivars (52% in 032 and 47% in BP). Where light intensity increased from 2000 to 8000 lux, 032 plants exhibited slightly increase in stem diameter and chlorophyll b while BP plants exhibited 9 and 21% decrease , respectively. In conclusion, cold stress in either 2000 or 8000 lux could adversely affect morphological parameters of soybean plants, however, the rate of damage increased at low light intensity.