Effect of leaf-to-fruit ratio on kernel quality formation of walnut trees

The study focused on the relationship between leaf-to-fruit ratio (LFR) and walnut kernel quality in <i>Juglans regia</i> ‘Wen 185’. It was investigated how LFR influences single kernel weight, the contents and percentages of organic matter in kernels, the 13C distribution proportion (¹³<i>C</i>_DP) in crude fat and protein, and the number and size of oil bodies within the kernels. A gradually decreasing LFR led to reduced single kernel weight, the contents of crude fat, crude protein, and soluble sugar dramatically (<i>P</i> < 0.05), with no significant changes in the percentages and (¹³<i>C</i>_DP) of crude fat, crude protein, and soluble sugar (<i>P</i> > 0.05). Moreover, there were no significant differences in the number of oil bodies per unit area and the size of oil bodies in kernel cotyledons and endosperm storage cells among the different LFR (<i>P</i> > 0.05). We propose that the walnut kernel quality depends on the proportion of sugar converted into fat and protein in the kernels, that the changes in LFR affect the amount of sugar accumulated in kernels but not the proportion of sugar converted to fat and protein, and that the LFR, therefore, have no effect on the percentages of crude fat and crude protein in walnut kernels.