ASGSB 1998 Annual Meeting Abstracts

[48]
LOW OXYGEN ALTERATIONS IN ARABIDOPSIS LEAF STRUCTURE RESEMBLE BRASSINOLIDE-DEFICIENT MUTANTS.  K.M. Ramonell and M.E. Musgrave. Dept. Plant Pathology & Crop Physiology, Louisiana State University, Baton Rouge, LA.

Plants are the foundation of the proposed Controlled Ecological Life Support System (CELSS) which NASA will utilize on future missions. It has been postulated that if plants could be grown under lower O₂ concentrations, their productivity might be increased due to a repression of photorespiration, resulting in increased crop yields. Previous studies in Arabidopsis thaliana grown under low O₂ have shown that at 2.5% O₂, plants exhibit a reduction in overall size as well as increases in stomatal density and distribution across the leaf surface. The A. thaliana mutant det2, which is defective in brassinolide synthesis, also exhibits reduced size. Since brassinolide synthesis has five O₂-requiring steps, its synthesis may be inhibited under low O₂. In this study, the stomatal density of the det2 mutant, its relationship to the stomatal density of A. thaliana grown under low O₂, and the ability of brassinolide to rescue det2 were investigated. A. thaliana var. ‘Columbia’ and det2 were grown on media alone or media supplemented with 10^-6M, 10^-7M, 10^-8M brassinolide in magenta vessels receiving 200 mol/m²/s¹ PAR at 25 C for 12 days. Leaves were examined using scanning electron microscopy and statistical analysis was performed. The leaves of det2 show similar patterns of increased stomatal density and aberrant stomatal pairing to leaves grown under 2.5% O₂. When supplemented with 10^-7M brassinolide, the abaxial stomatal density of det2 leaves returns to wild-type levels. The leaf length of det2 also returns to wild-type levels at 10^-7M brassinolide. These data indicate that inhibition of plant growth and changes in leaf structure that occur under low O₂ may be caused by lack of brassinolide synthesis. Supplementation of plants grown under 2.5% O₂ with brassinolide may restore normal growth and development. (Supported by NASA grant #NAGW-3759 and the Louisiana Space Consortium).

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