果树学报2025，Vol.42Issue(2)：360-375,16.DOI:10.13925/j.cnki.gsxb.20240458
外源褪黑素对盐胁迫下石榴幼苗光合及抗氧化特性的影响
Effects of exogenous melatonin on photosynthetic and antioxidant proper-ties of young seedlings under salt stress conditions in pomegranate
摘要
Abstract
[Objective]The pomegranate,a significant economic forest fruit crop predominantly culti-vated in Northwest China,is favored by consumers due to its extensive nutritional and medicinal bene-fits.However,the escalating issue of land salinization has resulted in reduced pomegranate yields and diminished fruit quality,thereby significantly hindering the advancement of the pomegranate industry.While the selection and breeding of salt-tolerant plants,along with the application of transgenic plants,represent crucial strategies for enhancing and utilizing saline soils,these methods are constrained by their prolonged duration and inherent challenges.In recent years,melatonin(MT)has emerged as a sig-nificant phytohormone capable of mitigating the detrimental effects of salt stress on plants.This study aims to examine the impact of exogenous MT on the photosynthetic characteristics and antioxidant ca-pacity of pomegranate(Punica granatum L.)seedlings subjected to salt stress,with a focus on identify-ing the optimal concentration for alleviating such stress.[Methods]Tunisian Soft-seeded(salt-sensi-tive)and Yecheng Acid(salt-tolerant)pomegranates were used as test materials,and the potting culture with substrate(vermiculite∶perlite∶grass charcoal=1∶1∶1,V/V/V).was adopted Six treatments were set up,namely,non-salt stress(CK),200 mmol·L-1 NaCl(T1),200 mmol·L-1 NaCl+50 μmol·L-1 MT(T2),200 mmol·L-1 NaCl+100 μmol·L-1 MT(T3),200 mmol·L-1 NaCl+150 μmol·L-1 MT(T4),and 200 mmol·L-1 NaCl+200 μmol·L-1 MT(T5)to investigate the effects of different concentrations of MT treatments.This study examined the impact of varying concentrations of melatonin(MT)on chloro-phyll content,photosynthetic gas exchange parameters,chlorophyll fluorescence,osmoregulatory sub-stances and antioxidant capacity in the leaves of two pomegranate seedling cultivars over treating dura-tions of 5,10 and 15 days.Additionally,to identify key physiological indicators of exogenous MT ef-fects on pomegranate seedlings under salt stress conditions,a correlation analysis and principal compo-nent analysis were conducted on 16 physiological indices from the two pomegranate cultivars.[Re-sults]Exposure to 200 mmol·L-1 salt stress resulted in a significant reduction in leaf chlorophyll con-tent(Chl a,Chl b and Chl a+b)and peroxidase activities(SOD,POD and CAT)in both cultivars.The application of melatonin(MT)significantly enhanced chlorophyll content and peroxidase activities.Nevertheless,the Yecheng Acid cultivar exhibited a certain degree of salt tolerance compared to the Tu-nisian Soft-seeded cultivar,despite the occurrence of electrolyte leakage.At 15 d of salt stress,applica-tion of exogenous MT at suitable concentrations(100 and 200 μmol·L-1)effectively enhanced net photo-synthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),photochemical quenching coeffi-cient(qP),actual photochemical efficiency(YⅡ),and maximal photochemical efficiency(Fv/Fm)in pomegranate leaves,and the Tunisian Soft-seeded pomegranate increased by 32.89％-45.06％,16.40％-37.49％,26.09％-53.10％,0.41％-19.90％,28.44％-48.04％and 11.89％-20.39％,respectively,and Yecheng Acid pomegranate increased by 28.81％-42.47％,17.13％-34.06％12.50％-37.78％,2.94％-20.59％,46.59％-48.58％,and 24.93％-32.00％,respectively.Under salt stress conditions,pomegranate leaves exhibited a significant increase in electrolyte extravasation(REC)and malondialdehyde(MDA)content compared to the control(CK).The application of melatonin(MT)resulted in a maximum reduc-tion of REC and MDA by 12.22％and 28.91％,respectively.Nonetheless,the application of a high con-centration(400 μmol·L-1)of exogenous MT exacerbated oxidative and osmotic stress,ultimately impair-ing the photosynthetic capacity of the seedlings.This may be related to the disruption of intracellular ionic homeostasis by high concentrations of MT.Principal component analysis showed that Pn,T,Gs,Ci,Chl a,Chl b,Chl a+b,qP,NPQ,Fv/Fm,YⅡ,REC and MDA were representative physiological indices of exogenous MT on pomegranate seedlings under salt stress conditions.[Conclusion]Salt stress in-duced several detrimental effects on pomegranate seedlings,including the restriction of photosynthesis and fluorescence mediation,a decrease in antioxidant enzyme activities and oxidative damage to cell membranes.Following the exogenous application of melatonin(MT)treatment,there was a significant enhancement in the photosynthetic parameters and chlorophyll content of the pomegranate seedlings.Additionally,the intercellular CO2 concentration was reduced,and stomatal conductance increased,thereby improving the photosynthetic rate and the photochemical efficiency of photosystem Ⅱ(PS Ⅱ).The antioxidant capacity of pomegranate seedlings was augmented through the upregulation of antioxi-dant enzyme activities,resulting in a significant reduction in relative electrolyte conductivity(REC)and malondialdehyde(MDA)levels.This reduction provided protection to the seedlings against membrane peroxidation damage induced by salt stress.A comprehensive evaluation using the rank sum ratio meth-od indicated that exogenous melatonin(MT)concentrations of 200 μmol·L-1 and 100 μmol·L-1 were most effective in mitigating salt stress injury in Tunisian Soft-seeded pomegranate and Yecheng Acid pomegranate,respectively.关键词
石榴/褪黑素/盐胁迫/光合特性/抗氧化特性/综合评价Key words
Pomegranate/Melatonin/Salt stress/Photosynthesis characteristic/Antioxidant properties/Comprehensive evaluation分类
农业科技引用本文复制引用
杨元玲,刘慧英,关思慧,柴亚倩,盖昊圣,刘明轩,刘阳,刁明..外源褪黑素对盐胁迫下石榴幼苗光合及抗氧化特性的影响[J].果树学报,2025,42(2):360-375,16.基金项目
新疆生产建设兵团科技攻关重点项目(2021AB015) （2021AB015）
