Speakers

Biography

Jeremiah Hlahla is a South African PhD student in Botany (plant stress physiology) at the University of the Free State (UFS, South Africa). He holds a Bachelor of Science (BSc) in Botany and Biochemistry (University of Johannesburg, South Africa). Honours in Botany (Marine ecology) from Nelson Mandela University (South Africa), and a Master of Science (MSc) degree in Botany (Plant Stress Physiology) from the UFS. He currently works as a research assistant at UFS and does a lot of work in plant physiology. His master's program investigated the effect of drought stress on the physiology and biochemistry of six edamame cultivars. In his PhD, he investigates the impact of combined drought and heat (DH) stress on three edamame cultivars' biochemistry, physiology, morphology, and yield. 

Abstract

In nature, drought and heat stress often co-exist. However, previous studies focus on the effects of such stresses separately. Edamame is a nutritious legume but sensitive to drought stress. There is a knowledge gap in edamame's physiological and biochemical responses to combined drought and heat (DH) stress. Therefore, this study compared three edamame cultivars (UVE14, UVE17, AGS429) in terms of their photosynthesis efficiency and some metabolites of osmotic adjustment under drought and heat separately, and DH stress at two growth stages (flowering and pod filling). Non-destructive handheld instruments were used to determine the photosynthetic efficiency in a greenhouse and destructive methods were used to quantify the chloroplast pigments, non-structural carbohydrates, and proline content spectrophotometrically. The DH stress had a more negative impact than drought or heat stress alone in edamame as it affected the photochemistry at both growth stages. Chloroplast protection by carotenoids resulted in AGS429 having more photosynthetic pigments and NDVI, thus a higher rate of photosynthesis than the other cultivars. Cultivar UVE17 had most of its reaction centers deactivated under DH stress and thus had the lowest photosynthetic efficiency of all cultivars at both growth stages. In addition, cultivars AGS429 followed by UVE14 performed better because they accumulated starch, maintained glucose balance through starch hydrolysis, and accumulated trehalose and proline, which resulted in high osmoregulation. In contrast, the cessation of UVE17 to accumulate proline at pod filling could have reduced Osmo protection and poor photosynthesis. Plant breeders can use this knowledge to select traits that confer tolerance to DH stress.