The aim of study was to characterize patterns of interception and distribution of photosynthetically active radiation (PAR) in an apple orchard and to examine its relationship with morphophysiological characteristics of “Royal Gala” and “Fuji Suprema” apple trees. The experiments were conducted during three production cycles in two distinct orchard areas, one covered by black anti-hail netting and another uncovered (control). We analyzed PAR characteristics with data from meteorological sensors installed on the canopy, as well as growth, anatomical, and physiological variables of apple trees. The reduction of PAR by netting influenced the components of radiation balance. PAR intercepted, absorbed, transmitted, and reflected by the canopy under netting decreased by 33%, 31%, 32%, and 46%, respectively, in comparison to uncovered canopy. When leaf area index (LAI) was 1.5 (under netting) and 2.5 (uncovered), maximum PAR interception efficiency was reached. During the three production cycles, a light extinction coefficient of 1.09 and 0.76 was found under netting and in the control, respectively. Plant height was greater under netting in all three cycles for both cultivars. Number of leaves, LAI, and shape index did not differ between treatments. At stage 85, leaves of “Royal Gala” under netting showed lower chlorophyll content and thinner parenchymas in comparison to the control. However, physiological and anatomical characteristics of Fuji “Suprema” did not change under anti-hail netting.

中文翻译：

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太阳辐射对巴西温带气候下苹果树生长、解剖和生理的影响

研究的目的是表征一个苹果园中光合有效辐射 (PAR) 的截获和分布模式，并研究其与“皇家盛会”和“富士至尊”苹果树形态生理特征的关系。实验在三个不同的果园区域进行了三个生产周期，一个覆盖着黑色防冰雹网，另一个未覆盖（对照）。我们使用来自安装在树冠上的气象传感器的数据以及苹果树的生长、解剖和生理变量分析了 PAR 特征。通过结网降低PAR影响了辐射平衡的组成部分。与未覆盖的冠层相比，网状冠层拦截、吸收、传输和反射的 PAR 分别降低了 33%、31%、32% 和 46%。当叶面积指数（LAI）为1.5（网下）和2.5（未覆盖）时，达到最大PAR截留效率。在三个生产周期中，发现网状和对照下的消光系数分别为 1.09 和 0.76。两个栽培品种的所有三个周期中的网状植株高度都较高。叶片数、LAI 和形状指数在处理之间没有差异。在第 85 阶段，与对照相比，网罩下的“Royal Gala”叶片叶绿素含量较低，薄壁组织较薄。然而，在防冰雹网下，富士“Suprema”的生理和解剖特征并没有发生变化。分别在网下和对照中发现了 76 个。两个栽培品种的所有三个周期中的网状植株高度都较高。叶片数、LAI 和形状指数在处理之间没有差异。在第 85 阶段，与对照相比，网罩下的“Royal Gala”叶片显示出较低的叶绿素含量和较薄的薄壁组织。然而，在防冰雹网下，富士“Suprema”的生理和解剖特征并没有发生变化。分别在网下和对照中发现了 76 个。两个栽培品种的所有三个周期中的网状植株高度都较高。叶片数、LAI 和形状指数在处理之间没有差异。在第 85 阶段，与对照相比，网罩下的“Royal Gala”叶片显示出较低的叶绿素含量和较薄的薄壁组织。然而，在防冰雹网下，富士“Suprema”的生理和解剖特征并没有发生变化。