Document: JUN-3-34-22

Field studies on the effects of UV-B radiation on leaf anatomy and morphology of Liquidambar styraciflua and Pinus taeda .

TIAN, J.* and J.SULLIVAN

Univ of Maryland, College Park, MD USA ¹

Abstract:
We investigated whether UV-B radiation would alter the anatomical or morphological properties of sweetgum (Liquidambar styraciflua) or loblolly pine (Pinus taeda) under field conditions as part of a multi-season project. Of particular interest were possible changes in leaf epidermal cells of these species. Sweetgum and loblolly pine seedlings were grown in the field for three years under three levels of UV-B radiation supplied by modulated irradiation systems. In order to assess whether UV-B effects were cumulative and persistent, one-half of the plants were switched among treatments in the second season. Leaf impressions were observed under a light microscope in order to determine epidermal cell size and density. Stomata size and density were also determined by analysis of leaf impressions. Scanning electronic microscopy (SEM) was used to examine epidermal cell size and epidermal cell wall thickness. The results on leaf morphology were consistent with those previously published in that UV-B exerted subtle effects on the rate of development and leaf size. Neither stomatal density or size were altered by UV-B in loblolly pine, but stomatal density was altered by UV-B in sweetgum. The SEM results indicated that adaxial epidermal cell wall thickness was increased by UV-B in both species. As expected, the effects of UV-B on epidermal anatomy or stoma were not cumulative and were affected only during development by the incident UV-B radiation levels. However, the affects of exposure to UV-B during leaf development may be important during subsequent growing seasons in loblolly pine, and perhaps other conifers, that retain their photosynthetic biomass over several years. The long-term effects of UV-related developmental changes warrant further investigation.

Keywords: UV-B radiation, Modulated systems, Anatomy, Morphology, Sweetgum, Loblolly Pine, Field study, SEM, Leaf impression

This abstract is being presented at: 10:30 AM in session:
Poster Session #14: UV-B.