Effect of Leaf Age and Cultivation under Shade Nets on the Ionome and Leaf Disorders in Phlox paniculata

Visual leaf damage symptoms affect plant and flower development. A variety of physiological leaf symptoms are induced by environmental and growing conditions, including light intensity during cultivation and the nutrition status of the leaves. In the present study, we studied effects of leaf age, leaf ionome, and shade factor during cultivation (20% and 47% shade – under shade nets), on the development of leaf disorders in two cultivars of Phlox paniculata. The leaf ionome of both cultivars changed with leaf age, and varied between cultivars. The percentage of shade applied during cultivation by shade nets, had a minor effect on the leaf ionome, and it did not affect the type and severity of the leaf disorders that developed on the plants, nor the stage of development of their appearance. The ionome of young leaves and mature leaves that were affected by a purple spotting disorder was similar to that of ‘healthy’-looking leaves, demonstrating that this disorder is not related to the nutritional status of the tissue. Our results further excluded leaf age, plant age, plant trimming and shade factor during cultivation (by shade nets) as inducers of the purple spots disorder. This study is first to explore the ionome of Phlox paniculata and in relation to leaf age, physiological leaf disorders and shade factor during cultivation.