Abstract
The vigorous growth of the new shoots of the peach tree was not beneficial to high quality and efficient cultivation. High concentration of amino acids can inhibit plant growth, but the mechanism is not clear. In this study, we explored the regulatory effects of seven amino acids (phenylalanine, valine, leucine, isoleucine, serine, D-alanine, and proline) (10 g⋅L–1) on the growth of peach trees. The results showed that phenylalanine, valine, and proline inhibited peach seedling growth and valine has the most significant effect and it can promote the root growth of peach seedlings. Compared with paclobutrazol, valine treatment improves net photosynthetic rate and fruit quality without reducing shoot diameter or puncture strength, and it does not affect leaf morphology. Valine enhanced the expression of PpSnRK1 (sucrose non-fermenting-1-related protein kinase) and inhibited the expression of PpTOR (Target of Rapamycin) and PpS6K (Ribosomal S6 kinase). The gibberellin content was significantly reduced in the valine treatment group. The endogenous valine content of peach seedlings was increased, acetohydroxyacid synthase (AHAS, E.C. 2.2.1.6) activity was inhibited by feedback, isoleucine synthesis was decreased, the relative amounts of branched chain amino acids were unbalanced, and growth was inhibited. However, isoleucine spraying after valine treatment could increase the content of isoleucine and alleviate the inhibition of valine on the shoot growth. In conclusion, valine is environmentally friendly to inhibit the growth of new shoots of peach trees by regulating the balance of PpSnRK1 and PpTOR and the synthesis of isoleucine.
Highlights
The vigorous growth of the new shoots of the peach tree leads to labor-consuming and timeconsuming for plastic trimming, and is not conducive to the improvement of the ventilation and light transmission conditions of the tree (Hao, 2017)
Past studies of the effects of amino acids have mainly focused on plant growth promotion (He et al, 2019; Kitir et al, 2019; Wang et al, 2019), whereas less is known regarding their roles in plant growth inhibition (Forsum et al, 2008; Näsholm et al, 2009; Xu et al, 2018)
We found that 10g·L−1 valine inhibited the activity of acetylhydroxylate synthetase (AHAS), decreased isoleucine synthesis, and unbalanced the relative levels of branched chain amino acids
Summary
The vigorous growth of the new shoots of the peach tree leads to labor-consuming and timeconsuming for plastic trimming, and is not conducive to the improvement of the ventilation and light transmission conditions of the tree (Hao, 2017). How to control the growth of new shoots effectively is very important to regulate the relationship between vegetative growth and reproductive growth of peach. Previous studies in our laboratory showed that too high or too low concentration of amino acids (1–50 g·L−1) would not produce obvious stress effect on plant growth. Past studies of the effects of amino acids have mainly focused on plant growth promotion (He et al, 2019; Kitir et al, 2019; Wang et al, 2019), whereas less is known regarding their roles in plant growth inhibition (Forsum et al, 2008; Näsholm et al, 2009; Xu et al, 2018)
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