龙安柚不同施肥处理对叶片结构和光合特性的影响

Effects of Different Fertilization Treatments on Leaf Structure and Photosynthetic Characteristics of Citrus grandis var. Longanyou

摘要: 对12年生龙安柚果园进行4种不同施肥处理，通过分析叶片质量、光合特征参数及其相关性，以揭示不同施肥处理下龙安柚光合能力对产量形成的影响规律，为龙安柚栽培中施肥管理提供理论依据。结果表明：1)不同物候期，处理2 (T2)营养枝和结果枝的叶厚、叶面积均较大，而CK最小，其中萌芽期和果实成熟期差异比较显著。此外，T2的比叶重、叶片干物质含量均较大，其中，果实成熟期的比叶重显著高于其他(P < 0.05)，营养枝和结果枝分别达到18.92 mg•cm⁻²和16.56 mg•cm⁻²；但其他物候期各处理与对照间差异不显著。说明T2处理叶片厚，叶面积大，比叶重大和叶片干物质含量高，有利于有机养分的制造和贮藏，是产量提高的原因之一。2)不同物候期，施肥处理的营养枝和结果枝叶片中叶绿素a、b、(a+b)和类胡萝卜素含量均显著高于对照，但各施肥处理间差异不显著。说明施肥处理能显著提高叶片中光合色素的含量。3)不同物候期，施肥处理叶片的净光合速率(Pn)均大于对照，且不同物候期的变化多呈单峰曲线。其中，不同处理营养枝叶片的Pn最大值均出现在果实膨大期，且以T2最大(7.59 µmol•m⁻²•s⁻¹)；而结果枝叶片的Pn最大值出现在生理落果期。此外，不同处理的营养枝和结果枝叶片的Tr、Gs与Pn的变化规律类似，而Ci变化趋势则与Pn相反，呈现倒峰曲线。说明T2施肥方案有利于提高龙安柚叶片中碳水化合物的积累，从而保障树体营养生长和生殖生长。4)果实成熟期Pn与Chl a、Chl b、Car正相关达显著水平，且回归分析表明光合速率与叶绿素含量间存在良好的线性关系。综上，处理2有利于改善叶片性状，提高叶片净光合速率，为龙安柚产量形成奠定了良好的基础。

Abstract: The 12-year-old Citrus grandis var. longanyou orchard was subjected to four different fertiliza-tion treatments. By analyzing the leaf quality, photosynthetic characteristic parameters and their correlation, the effect of different fertilization treatments on the photosynthetic capacity of Longanyou on yield formation was revealed, which was used to cultivate Longanyou. The fertilization management provides the theoretical basis. The results showed that: 1) In different phenophases, the leaf thickness and leaf area of Treatment 2 (T2) vegetative shoots and fruiting branches were larger, while CK was the smallest, among which the difference of germination period and fruit ripening period was significant. In addition, the specific leaf weight and leaf dry matter content of T2 were relatively large. Among them, the specific leaf weight at the fruit ripening stage was significantly higher than that of the others (P < 0.05). The vegetative shoots and fruiting shoots reached 18.92 mg∙cm⁻² and 16.56 mg∙cm⁻², respectively. But in other periods, the difference between treatment and control was not significant. This shows that T2 treatment is characterized by thicker leaves, larger leaf area, higher specific leaf weight and higher dry matter content, which is beneficial to the production and storage of organic nutrients, which is one of the reasons for the increase in yield. 2) The contents of chlorophyll a, Chl b, Chl (a+b) and carotenoids in the vegetative shoots and the resulting shoots were significantly higher than those of the control at different phenological stages, but there was no significant difference among the treatments. It shows that the fertilization treatment can significantly increase the content of photosynthetic pigments in leaves. 3) At different phenophases, the net photosynthetic rate (Pn) of fertilized leaves was higher than that of the control, and the changes of different phenophases showed a single peak curve. Among them, Pn maxima of different treatment vegetative shoots appeared in fruit enlargement period, and the maximum value of T2 was (7.59 μmol∙m⁻²∙s⁻¹). The maximum Pn value of the resulting branch twigs appeared in the physiological fruit drop period. In addition, the changes of Tr, Gs, and Pn in the vegetative shoots and the resulting shoots with different treatments were similar, while the change trend of Ci was opposite to that in Pn, showing an inverted peak curve. This shows that the T2 fertilization scheme is beneficial to improve the carbohydrate accumulation in the leaves of Longanyou, so as to ensure the vegetative growth and reproductive growth of the tree. 4) Pn was positively correlated with Chl a, Chl b, and Car at fruit ripening stage, and regression analysis showed that there was a good linear relationship between photosynthetic rate and chlorophyll content. In summary, treatment 2 is beneficial to improve the leaf traits and increase the net photosynthetic rate of leaves, which lays a good foundation for the formation of Longanyou production.