阳光玫瑰葡萄叶片发育与衰老期间矿质营养与光合能力变化及相关性研究

Changes in mineral nutrients and photosynthetic capacity and their correlations during leaf development and senescence in Shine Muscat grape

【目的】掌握葡萄叶片光合能力和矿质营养变化规律,探明影响光合功能的关键营养因子。【方法】以平棚架式4~5年生5BB砧阳光玫瑰植株为研究试材,于采后生长季节(9月中)测定同一枝不同节位叶片净光合速率(P_(n))及其矿质元素含量;在入秋后追踪固定节位(第8节位)叶衰老过程中P_(n)、SPAD值和矿质营养含量,进行相关性分析。【结果】第8节位P_(n)达到与最大值无显著差异水平,说明该节位叶片已经发育充分成熟,而同枝条上衰老叶SPAD和P_(n)显著下降。叶片氮、磷、钾、铜在第8节位后达到稳态,而钙和锰则随叶位升高(叶龄)呈积累趋势。9月中的衰老叶的氮、磷、钾、锌、硼、铜元素内吸收率分别为44.6%、44.4%、71.1%、25.8%、24.6%和10.5%,钙、铁、镁、锰内吸收率接近0或为负值。不同节位叶片锰含量与P_(n)值呈显著正相关。入冬衰老叶片仅氮、锌、钾元素含量有所降低,其余营养元素再利用率均为负值,氮含量与P_(n)呈显著正相关。【结论】阳光玫瑰在生长季节可移动元素再利用率较高,入冬后衰老叶片矿质再利用能力全面降低。锰可能是叶片光合能力形成的限制性营养因子,氮可能是老叶光合能力维持的关键营养因子。

【Objective】In recent years,grape production has expanded rapidly in Guangdong province,where climate allows over 9 months of growth season for grape.Leaf senescence and abscission occur in Guangdong much later than in traditional production regions further north.In some cultivars like Shine Muscat and Oriental Star,there is no complete leaf shed throughout winter.During the active growth season,leaf senescence frequently occurs with the ripening of the berry.Mineral nutrients play important roles in performing photosynthetic functions.It is worth to examine mineral nutrient changes in leaves during development and senescence.Also,there has been no study on comparing patterns of mineral changes in senescing leaves during growth season and during short-day induced systematic leaf senescence in late fall.The present study was conducted to understand the change patterns of photosynthetic capacity and mineral nutrients in leaves of Shine Muscat grape during leaf development and senescence and analyze their correlations so as to find out the key elements for photosynthetic capacity development and maintenance during leaf maturation and senescence as well as the reutilization pattern of various nutrients during leaf senescence.These findings will provide important guidance for nutrient management in grape.【Methods】The experiment was carried out in the experimental grape orchard,South China Agricultural University,Guangzhou,China,in 2019 and 2020.Four-to five-year-old Shine Muscat vines on 5BB rootstocks in pergola trellis were used as the experimental materials.One month after berry clusters were harvested,leaves at all nodes of five canes from different vines were sampled during the postharvest tree recovery period in mid September 2019 after they were individually measured for net photosynthetic rate(P_(n))with a CIRAS-3 photosynthesis system(PP systems,Amesbury,MA,USA)and chlorophyll index(SPAD value)with an a SPAD-502 portable chlorophyll meter(Minolta,Osaka,Japan).All the measurements were made from 9:00 to 11:00 in the morning in a clear day.The sampled leaves were then taken into the laboratory and individually washed with clean water and oven-dried at 65℃for 3 days before used for mineral nutrient analysis.In late September 2020,a functional mature leaf at the 8^(th) node from the tip on 3 canes with each of five vines was tagged for tracing changes in SPAD and photosynthetic parameters from late September to late December at an interval of one month.Leaves at the same node of neighboring canes were sampled for nutrient analysis in late September and late December.Based on differences in mineral nutrients between the functional leaves and the senesced leaves,the resorption rate,which reflects the remobilization ability of nutrients in senescing leaves,was calculated.【Results】(1)Leaf P_(n) and SPAD values increased as the node position increased.At node 8,P_(n) value reached a level similar to its maximum value obtained in leaf at node 16,while SPAD increased to a maximal value at node 10 and maintained relatively stable in older leaves,suggesting leaves at the 10^(th) node were fully mature.The senesced and yellowed leaves on the same canes showed significantly reduced P_(n) and SPAD values compared with the leaves at the 16^(th) node.(2)Concentrations of nitrogen,phosphorous,potassium and copper decreased initially with leaf expansion but maintained stabilized from node 8 up;calcium and manganese accumulated with leaf age and were the highest in the old senescing leaves;iron content decreased during leaf expansion but accumulated later;the remaining elements(magnesium,zinc and boron)showed no defined pattern.(3)During the growth season in mid-September,the yellowed and senescing leaves had lower contents of nitrogen,phosphorus,potassium,zinc,boron and copper compared with the functional mature leaf at the 16^(th) node with the highest P_(n) value.The resorption rates of nitrogen,phosphorus,potassium,zinc,boron and copper in senescent leaves were 44.6%,44.4%,71.1%,25.8%,24.6%and 10.5%,respectively,indicating these mineral nutrients in senescing leaves can be remobilized at different degrees;the resorption rates of magnesium,manganese,calcium and iron were close to zero or negative,indicating that these mineral nutrients can hardly be reutilized.(4)Correlation analysis between P_(n) and mineral nutrients contents in functional leaves at different nodes showed that only manganese had a significant and positive correlation with P_(n).Manganese content and P_(n) could be perfectly regressed into a quadratic equation(R^(2)=0.6525,p=0.003),with a maximal P_(n) value occurring when manganese content was 66.96 mg·kg^(-1).(5)During winter,systemic leaf senescence occurred in the vines,and only nitrogen,zinc and potassium had a positive resorption rate(24.3%,18.4%and 0.6%,respectively),while those of phosphorus,calcium,magnesium,copper,iron,manganese and boron were all negative,indicating that these elements accumulated with leaf senescence in winter and that these nutrients may loss as the leaves drop in winter.(6)During the senescence of leaves in winter,nitrogen was the only nutrient with a significant and positive linear correlation(R^(2)=0.457,p=0.032)to P_(n).【Conclusion】Based on the above results,the following conclusions could be drawn:(1)Leaf at the 8^(th) node from the cane apex becomes fully mature and photosynthetic function maintains its maximal level until leaf senescence.(2)During the growth season,nitrogen,phosphorous,potassium,zinc and boron are remobilized in senescing leaves of Shine Muscat grape,but calcium,iron and manganese are not remobilized and accumulated with leaf aging.In winter,systematic leaf senescence occurs,and the mobilizability of all mineral nutrients from senescing leaves loses or becomes weaker in Guangzhou.(3)During the development of young leaves,manganese may be a limiting nutrient element for the formation of photosynthetic capacity in Shine Muscat leaves,while in old leaves,nitrogen serves as the key nutrient element for maintaining photosynthetic capacity.