Abstract
Phytohormones play important roles in germination, blossom, senescence, abscission of plants by a series of signal transduction and molecular regulation. The purpose of this research was to investigate the influence of root restriction (RR) cultivation on plant endogenous hormone variation tendency at different growth stages in diverse organs or tissues. ‘Muscat Hamburg’ (Vitis ‘Muscat of Alexandria’ × Vitis ‘Trollinger’) grapevine was used as test material. High Performance Liquid Chromatography (HPLC) was used to quantify hormone levels, qRT-PCR was used to quantify the expression of genes related to hormone biosynthesis pathway, and determined parameters of growth and photosynthetic, aiming to investigate the influence of root restriction on the formation and metabolism of phytohormones, as well as the degree of correlation between phytohormones and plant growth and photosynthetic intensity under root restriction. By measuring the photosynthetic rate of leaves at the stages of core-hardening, veraison and maturity, it was found that root restriction could reduce most photosynthetic parameters. The results also revealed that RR treatment increased abscisic acid (ABA), salicylic acid (SA), zeatin riboside (ZR), N6-(delta 2-isopentenyl)-adenine nucleoside (iPR) concentrations, while reduced auxin (IAA), 3-indolepropionic acid (IPA), 3-indolebutyric acid (IBA), gibberellin A3 (GA3), zeatin (ZT), N6-(delta 2-Isopentenyl)-adenine (iP), kinetin (KT), jasmonic acid (JA) and methyl jasmonate (MeJA) concentrations in most organs and at most developmental stages. RT-qPCR was carried out to further explore the effect of root restriction on genes expression of ABA, SA and IAA biosynthesis pathways at molecular level. Meanwhile, through correlation analysis, we found that different phytohormones contributed differently to physiological indicators, there existed strong correlation of ABA, KT, MeJA, iPR, SA, JA with leaf photosynthesis, GA3, IBA, ZR, IAA, ZT with fruit quality. In addition, we also found that the shoot growth related parameters were closely correlated with JA, IPA and iP. To sum up, our results suggested that RR treatment could significantly increase soluble solid content, regulate the growth and photosynthesis of grapevine, by affecting the biosynthesis of phytohormones. It could further prove that root restriction was a feasible technique to ameliorate the phenomenon of low quality in grape berry in southern China.
Highlights
Phytohormones play important roles in germination, blossom, senescence, abscission of plants by a series of signal transduction and molecular regulation
In terms of IAA concentration, our results revealed that RR treatment could significantly decreased its concentrations in most stages and organs, indicating that RR treatment could inhibit the growth of grapevine, which led to grapevine phenotypes changed including shorter stem length or smaller berry vertical and horizontal diameter, these finding was consistent with previous studies implying that RR treatment could reduce IAA concentration in g rapevine[43]
We found G A3 concentrations were higher in root and leaf than other organs, directly confirming the biosynthesis sites of GA might mainly concentrated in root or leaf
Summary
Phytohormones play important roles in germination, blossom, senescence, abscission of plants by a series of signal transduction and molecular regulation. A thorough research in exploring the variation tendencies of endogenous hormones including IAA, IBA, IPA, CTKs, GA, ABA, JA, MeJA was performed, and a thorough research in investigating correlation between phytohormones and grape physiological parameters was necessary, above results will better understand the action mechanism and effect with RR treatment. A total of 27 physiological parameters of ‘Muscat Hamburg’ (Vitis ‘Muscat of Alexandria’ × Vitis ‘Trollinger’) grape were measured, 13 endogenous hormone concentrations during four growth stages (I: Budbreak, II: Blossom, III: Veraison, IV: Maturity) in different organs (bud, root, berry, flower, stem, leaf) were analyzed by HPLC, and ABA, IAA and SA biosynthesis related genes were quantified by qRTPCR, aiming to investigate the impact of RR treatment on the concentrations of endogenous hormones. Inquired the relationship between root restriction and changes in physical parameters and plant endogenous hormone concentrations, as well as their relational degree
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