2种晚实核桃光合特性及产量变化

Studies on photosynthetic characters and their relationship with yield in two late season walnut cultivars

【目的】探讨2种晚实核桃(Juglans regia L.)光合特性及与产量之间的关系,为其丰产栽培提供理论依据。【方法】用便携式Li-6400光合仪和PAM-2100叶绿素荧光分析仪,以晚实核桃品种‘清香’‘晋龙1号’为试材,在自然条件下测定光合荧光参数及其产量变化。【结果】‘晋龙1号’和‘清香’净光合速率(Pn)日变化均为双峰曲线,在13:00出现显著的光合"午休"现象;光饱和点(LSP)分别为1 612.5、1 716.7μmol·m-2·s-1,光补偿点(LCP)分别为37.32、49.27μmol·m-2·s-1,表观量子效率(AQY)分别为0.031 8、0.037 6,最大净光合速率(Pmax)分别为11.40、18.68μmol·m-2·s-1。‘清香’具有较佳的光合能力。在13:00前后最大光能转化效率(Fv/Fm)、实际光化学效率(Yield)、光化学淬灭(q P)较低,非光化学淬灭(q N)较高,光合效率降低,光合系统受到一定程度的光抑制,但并无明显破坏。而‘清香’的Fv/Fm、q P、q N及Yield在全天几乎均高于‘晋龙1号’,表现出较好的光能转化效率和胁迫耐受性。2者在单株产量和平均公顷产量上也表现出极显著差异,‘清香’是‘晋龙1号’的1.77倍。【结论】2种晚实核桃中午Pn的下降由非气孔限制引起,光合能力与单株产量呈极显著正相关;其需要强光而对弱光响应不敏感的特性适宜稀植,从而提高核桃的产量。

[Objective]The purpose of the study was to explore the relationship between photosynthetic characters and productivity in two late season walnut eultivars in order to provide theoretical reference for high yielding cultivation. The changes in the photosynthesis, chlorophyll fluorescence and yield per plant in the two cultivars were studied in this experiment. [Methods]The two late season walnut cuhivars, ＇Qingxiang＇ and ＇Jinlongl＇, were used as the materials. The trees grown at a space of 5 rex6 m were ten years old and cultivated according to the conventional management. The soil was sandy loam, and water and fertilizer management was poor in orchard. Determination of changes in photosynthetic and fluorescence parameters, fruit yield and kernel yield per plant was under normal circumstances. Photosynthetic and envi- ronmental parameters were determined using a portable photosynthetic analyzer （Li-6400, USA） and a chlorophyll fluorescence analyzer （PAM-2100, Germany）. The experiment was conducted in July 2016 in a walnut orchard in south mountain of Chengxian, Longnan. The measurements were carried out on July 1 and 2, July 11 and 12 and July 21 and 22. Three grafted walnut seedlings were selected for each cultivar, and the fifth or sixth functional leaves of the middle compound leaves from three new branches in the same growth direction of the outer canopy of each tree were measured. The diurnal variation of photosyn-thesis was measured at one hour interval from 80＇ clock to 18 O＇ clock, and the parameters measured included net photosynthetic rate （Pn, μmol.m^-2.s^-1）, intercellular CO2 concentration （Cμmol. mol^-1）, stomatal conductance （Gs, mol. m^-2. s^-1）, and transpiration rate （Tr, retool- m-2＂ s-l）. Besides, the environmental parameters including atmospheric temperature （ta, ℃）, air CO2 concentration （Co, μmol.mol^-1）, atmospheric relative humidity （RH, %） and light intensity （PAR, μmol-m^-2.s^-1）, and water use efficiency （WUE, retool.mol^-1） were also collected. The light response curve of Pn was constructed by measuring Po at 2 000, 1 800, 1 600, 1 400, 1 000, 500, 200, 150, 100, 50, 20 and 0 Ixmol＂ m-2. s-1. SPSS software was used to obtain the regressed light response curve. According to the regression equation, light compensation point （LCP） and saturation point （LSP）, maximum photosynthetic rate （Proof）, and apparent quantum yield （AQY） could be obtained. The diurnal variations of fluorescence parameters were measured at one hour interval from 80＇ clock to 18 O＇ clock at the same time with the measurement of photosynthetic parameters. The fluores- cence parameters included PS II maximum photochemical efficiency （FJF,O, PS ]I photon yield （Yield）, photochemical quenching （qP）, non-photochemical quenching （qN） and so on. The number of fruit and yield in each investigated tree were collected when walnut were ripe. 30 fresh walnuts were randomly col- lected for calculation of the average single fruit weight after fully dried in the middle of September in the same year. Finally, walnut yield and kernel yield per plant were calculated. All the data were analyzed using Excel 2010 and SPSS 21.0. [Results]The diurnal changes in Po in both walnut cuhivars exhibited a double peak curve with a clear ＂mid-day rest＂ around 13 o＇clock. The LSP, LCP, AQY, and P,,lOX in ＇Jin- longl＇ and ＇Qingxiang＇ were 1 612.5 and 1 716.7 p^mol.m-2. s-1, 37.32 and 49.27 bl, mol＇m-2＂ s-1, 0.031 8 and 0.037 6, and 11.40 and 18.68 p, mol. m-2. s-1, respectively. The data indicated late season walnut trees need strong light and was insensitive to weak light, and therefore should be planted in low density. The variety of ＇Qingxiang＇ showed a higher photosynthetic capacity. FJFm, Yield, and qP were low, while qN was high around 13 O＇clock, when photosynthetic efficiency decreased with significant photoinhibition but no significant damage on photosynthetic system. Fv/F,,, qP, qN and Yield in ＇Qingxiang＇ were general- ly higher than in ＇Jinlongl＇ throughout the day, suggesting that the former had a better light conversion efficiency and stress tolerance and thus more suitable for planting in Longnan mountain. The yield per plant and yield per hectare were also significantly different between cultivars, and productivity of ＇Qingx- iang＇ was 1.77 times that of ＇Jinlongl＇. Pn, Fv/F.~, Yield, qP, qN and yield per plant of the two late season walnut cuhivars had strong correlations. [Conclusion]The mid-day decrease in Pn in both cultivars was caused by non-stomatal limitation under extreme environmental conditions. Photosynthetic capacity and plant productivity were significantly positively correlated. Their requirement for strong light with low sen- sitivity to low light indicated that they were suitable for sparse planting.