In an intriguing study by Niu et al., published in 2023, researchers examined the effects of two compounds, glycine betaine (GB) and cycloleucine (Cyc), on plant growth and development. These compounds, previously reported to influence animal cell metabolism, have been relatively understudied in plants.
The research focused on eggplant growth, photosynthesis, chlorophyll fluorescence, Calvin cycle pathway, leaf morphology, endogenous hormones, and amino acid content in response to foliar sprays of different glycine betaine concentrations and cycloleucine.
The researchers found that a 40 mmol L−1 concentration of glycine betaine had the most beneficial effect on plant growth and development. This concentration increased plants' fresh and dry weight, boosted the density of abaxial leaf hairs (hairs on the underside of leaves), and enhanced the net photosynthetic rate and activity of key enzymes in the Calvin cycle, a critical process in photosynthesis.
In addition, glycine betaine elevated chlorophyll fluorescence parameters and increased the content of endogenous indoleacetic acid (IAA, a plant hormone). It decreased abscisic acid (ABA, a plant hormone often associated with stress responses). It also increased the contents of several amino acids, including glutamate, serine, aspartate, and phenylalanine, which are crucial for plant metabolism and growth.
In contrast, cycloleucine demonstrated a significant inhibitory effect on plant growth. As the concentration of cycloleucine increased to 20 mmol L−1, plant apical dominance disappeared, plant height and dry and fresh weights decreased, and the development of abaxial leaf hairs was hindered. Cycloleucine also inhibited the Calvin cycle's net photosynthetic rate and critical enzyme activities. Moreover, cycloleucine led to a decrease in the endogenous hormones IAA and ABA and affected the conversion and utilization of several amino acids, including glutamate, arginine, threonine, and glycine.
In conclusion, the study suggests that while a 40 mmol L−1 concentration of glycine betaine enhances plant growth and development, a 20 mmol L−1 concentration of cycloleucine significantly inhibits these processes. This research contributes to understanding how specific compounds can influence plant growth and development, potentially leading to improved agricultural practices and crop productivity.
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