Research Articles (Plant Sciences)

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Browsing Research Articles (Plant Sciences) by Author "Hlahla, Jeremiah M."

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    Exploring edamame survival mechanisms under combined drought and heat stress: photosynthesis efficiency and carbohydrate accumulation
    (Elsevier, 2024) Hlahla, Jeremiah M.; Mafa, Mpho S.; van der Merwe, Rouxléne; Moloi, Makoena J.
    The combined drought and heat (DH) stress have devastating effects on plant physiological and biochemical processes, leading to poor yield. The aims of this study were to identify the physio-biochemical mechanisms employed by edamame (Glycine max L. Merrill) for survival and to establish better performing cultivars under DH stress. The impact of DH stress on the photosynthesis efficiency and osmolytes production in three edamame cultivars (UVE14, UVE17 and AGS429) was investigated. Non-destructive measurements were performed to determine the photosynthesis attributes, while pigments, non-structural carbohydrates (starch, glucose, sucrose, trehalose) and proline were extracted and quantified spectrophotometrically. The results showed that chlorophyll a (Chl-a), Chl-b, total chlorophyll and carotenoids in AGS429 were not affected under DH stress, which corresponded to increased normalised difference vegetative index (NDVI). Positive correlations between the carotenoids and total chlorophyll contents suggest that in AGS429, prevention of chlorophyll degradation under DH stress could be attributed to the increased carotenoids because they have antioxidative function. Additionally, AGS429 and UVE14 had increased trehalose, suggesting high osmotic adjustment under DH stress. An increase in starch production maintained glucose balance in AGS429 and UVE14, demonstrating higher photosynthetic efficiency compared to UVE17. The DH stress reduced photochemical reactions and carbohydrate accumulation in UVE17. This study shows that AGS429 and UVE14 protected the photosystems and photosynthetic pigments during DH stress, which led to higher photosynthetic capacity and accumulation of carbohydrates. Thus, maintaining the photosynthesis efficiency and carbohydrate metabolism processes in the AGS429 and UVE14 were adaptation features under DH stress.
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    The photosynthetic efficiency and carbohydrates responses of six edamame (Glycine max. L. Merrill) cultivars under drought stress
    (MDPI, 2022) Hlahla, Jeremiah M.; Mafa, Mpho S.; Van der Merwe, Rouxlene; Alexander, Orbett; Duvenhage, Mart-Mari; Kemp, Gabre; Moloi, Makoena J.
    Vegetable-type soybean, also known as edamame, was recently introduced to South Africa. However, there is lack of information on its responses to drought. The aim of this study was to investigate the photosynthetic efficiency and carbohydrates responses of six edamame cultivars under drought stress. Photosynthetic efficiency parameters, including chlorophyll fluorescence and stomatal conductance, were determined using non-invasive methods, while pigments were quantified spectrophotometrically. Non-structural carbohydrates were quantified using Megazyme kits. Structural carbohydrates were determined using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Drought stress significantly increased the Fv/Fm and PIabs of AGS429 and UVE17 at pod filling stage. Chlorophyll-a, which was most sensitive to drought, was significantly reduced in AGS429 and UVE17, but chlorophyll-b was relatively stable in all cultivars, except UVE17, which showed a significant decline at flowering stage. AGS354 and AGS429 also showed reduced chlorophyll-b at pod filling. UVE17 showed a significant reduction in carotenoid content and a substantial reduction in stomatal conductance during pod filling. Drought stress during pod filling resulted in a significant increase in the contents of trehalose, sucrose and starch, but glucose was decreased. Chlorophyll-a positively correlated with starch. The FTIR and XRD results suggest that the cell wall of UVE14, followed by UVE8 and AGS429, was the most intact during drought stress. It was concluded that carotenoids, stomatal conductance, starch and hemicellulose could be used as physiological/biochemical indicators of drought tolerance in edamame. This information expands our knowledge of the drought defense responses in edamame, and it is essential for the physiological and biochemical screening of drought tolerance.