UV radiation reduces epidermal cell expansion in leaves of Arabidopsis thaliana

Abstract

Plants have evolved a broad spectrum of mechanisms to ensure survival under changing and suboptimal environmental conditions. Alterations of plant architecture are commonly observed following exposure to abiotic stressors. The mechanisms behind these environmentally controlled morphogenic traits are, however, poorly understood. In this report, the effects of a low dose of chronic ultraviolet (UV) radiation on leaf development are detailed. Arabidopsis rosette leaves exposed for 7, 12, or 19 d to supplemental UV radiation expanded less compared with non-UV controls. The UV-mediated decrease in leaf expansion is associated with a decrease in adaxial pavement cell expansion. Elevated UV does not affect the number and shape of adaxial pavement cells, nor the stomatal index. Cell expansion in young Arabidopsis leaves is asynchronous along a top-to-base gradient whereas, later in development, cells localized at both the proximal and distal half expand synchronously. The prominent, UV-mediated inhibition of cell expansion in young leaves comprises effects on the early asynchronous growing stage. Subsequent cell expansion during the synchronous phase cannot nullify the UV impact established during the asynchronous phase. The developmental stage of the leaf at the onset of UV treatment determines whether UV alters cell expansion during the synchronous and/or asynchronous stage. The effect of UV radiation on adaxial epidermal cell size appears permanent, whereas leaf shape is transiently altered with a reduced length/width ratio in young leaves. The data show that UV-altered morphogenesis is a temporal- and spatial-dependent process, implying that common single time point or single leaf zone analyses are inadequate.

Interaction of cytokinins with UV-B (280 -315nm) on the expansion growth of cucumber cotyledons

“…130 The reduction in leaf size of UV-B exposed Arabidopsis plants has been associated to decrease in the cell expansion of the adaxial epidermal cells. 131 Jansen 105 found that the UV-B-induced reduction in plant growth, and more specifically in leaf area, has been attributed either to cell division or cell expansion or a combination of both. Some authors suggested that UV-B treatment reduced both the cell division and cell expansion in Pisum sativum, 71 Triticum aestivum, 132 & Trifolium repens.…”

Repression of Growth Regulating Factors by the MicroRNA396 Inhibits Cell Proliferation by UV-B Radiation in Arabidopsis Leaves

“…However, available data about the effects of UV-B radiation on cell proliferation and cell expansion are contradictory, probably reflecting differences in experimental conditions. Acute, stress-inducing UV-B conditions cause necrosis and inhibit cell proliferation, while lower doses and/or chronic UV-B treatments affect both cell proliferation and expansion (Staxen and Bornman, 1994;Nogués et al, 1998;Laakso et al, 2000;Hopkins et al, 2002;Hofmann et al, 2003;Kakani et al, 2003;Hectors et al, 2007Hectors et al, , 2010Wargent et al, 2009a;Robson and Aphalo, 2012). For example, fewer epidermal cells were observed after UV-B exposure in some species (Gonzalez et al, 1998;Hopkins et al, 2002); however, stimulation of cell proliferation by UV-B radiation has also been reported in petunia (Petunia hybrida; Staxen and Bornman, 1994), and increases in leaf thickness attributed to increases in the number of parenchyma cells were reported in Brassica carinata and Medicago sativa (Bornman and Vogelmann, 1991).…”

UV-B Inhibits Leaf Growth through Changes in Growth Regulating Factors and Gibberellin Levels

“…Existing data on the effects of UV-B on cell proliferation and cell expansion are contradictory, probably reflecting differences in experimental conditions. Acute, stress-inducing UV-B conditions usually inhibit cell proliferation, while both cell proliferation and expansion are affected by lower doses and/or chronic UV-B treatments (Staxen and Bornman, 1994;Nogués et al, 1998;Laakso et al, 2000;Hopkins et al, 2002;Hofmann et al, 2003;Kakani et al, 2003;Hectors et al, 2007Hectors et al, , 2010Wargent et al, 2009;Robson and Aphalo, 2012). For example, the number of epidermal cells at maturity decreased after UV-B exposure in some species (Gonzalez et al, 1998;Hopkins et al, 2002); on the contrary, in lettuce (Lactuca sativa) leaves, UV-B reduced cell expansion rate and final leaf size (Wargent et al, 2009).…”