Effect of ultraviolet-B radiation on the genes of garden cress leaves

Abstract

In order to determine the level of tolerance to ultraviolet-B radiation, the effects of different UV-B doses on leaf growth and development of garden cress (Lepidium sativum L.) were investigated. After three days of growth, the seedlings were cultivated under controlled environment conditions and exposed to 0, 1, 3, 5, 7 and 9 kJ/m² d UV-B radiation. Tolerance to UV-B was qualified by measuring these parameters: leaf number, total area, length, thickness, fresh and dry weight, anatomic-morphological and cytological characteristics. It was determined a significant stimulating impact of 1 kJ/m² d UV-B radiation on leaf growth. Compared with the control plants grown without UV-B radiation, the increase of the total leaf area reached 6%, thickness – 24%, length of the first leaf pair – 14%, fresh weight – 30%. Furthermore, the cell area of the mesophyll tissue increased by 31%, while that of the abaxial and adaxial epidermis – by 74% and 20%, respectively. An ambiguous leaf reaction was induced by the 3 kJ/m² d UV-B radiation. This UV-B dose reduced the growth of the first leaf pair and stimulated the growth and development of the second ones. However, the total leaf area was smaller by 30% and fresh weight – by 23% than analogous parameters of control plant leaves. UV-B radiation by 5-9 kJ/m² d doses inhibited the growth of the both leaf pairs, disrupted the abaxial leaf surface and provoked a dehydration of leaf tissues. The action of 3 kJ/m² d UV-B radiation and larger radiation doses induced the differentiation of the mesophyll into palisade and strong mesopyll layers though inhibited the expansion of leaf tissue cells. The data imply that garden cress plants are able to tolerate UV-B radiation up to 3 kJ/m² d dose under controlled environment conditions