ASGSB 1998 Annual Meeting Abstracts

[89]
STRUCTURAL AND FUNCTIONAL ORGANIZATION OF MESOPHYLL CELLS OF BRASSICA RAPA PLANTS GROWN IN MICROGRAVITY.   N.I. Adamchuk¹, E.L. Kordyum¹, and J.A. Guikema^{2 1}Institute of Botany, Nat. Acad. Sci. of Ukraine, Kiev, Ukraine, and ²Kansas State University, Manhattan, Kansas, USA.

Comparative light- and electron-microscopic analysis of structural and functional characteristics of mesophyll cells and chloroplast components in first true leaves of 6, 9, 13, 15-day Brassica rapa plants. These plants were grown on earth or in microgravity aboard the space-shuttle Columbia on STS-87. Several differences were observed when the flight samples were compared with the relevant ground controls. We observed an increase in the mesophyll thickness, the palisade cell volume, the number of organelles such as the chloroplasts, mitochondria and peroxysomes per cell. We noted a difference in the relative volume of photosynthetic membranes as well. Substantial differences in the photosynthetic tissues was determined after two weeks of plant growth in microgravity. Spaceflight conditions caused an increase in the ratio of palisade/spongy parenchyma of 27%, and apparently increased the palisade cell volume by 12.5% and the intracellular space by 10.3%. The number of cells which contained chloroplasts with vesicular thylakoids increased approximately 1.7 folds in microgravity in comparison with that in the ground control. Differences in the chloroplast substructure included a reduction in the grana number, and an increase in both the intrathylakoid space and starch grain size. These features could cause aberrant electron transport activity in both photosystems 1 and 2, and could alter photosynthetic efficiency. These features will be discussed in light of the relationship of structure to function in the photosynthetic processes, and in light of how the space environment may perturb this relationship.

Back to Meeting Program