TOLERANCE OF TOMATO GENOTYPES TO OSMOTIC STRESS IN VITRO (TISSUE CULTURE, WATER, SODIUM-CHLORIDE)
Abstract
Growth of cultured cells of the cultivated tomato Lycopersicon esculentum Mill var. Knox and its wild relative Solanum pennellii Corr. when exposed to osmotic stress (water and salt) was compared in order to evaluate cellular mechanisms of tolerance to these stresses. Water stress and salinity were imposed using polyethylene glycol (PEG, M.W. 6000) and NaCl. For both genotypes major differnces in the growth of cells in media with PEG or NaCl occurred as a function of the growth cycle states, with cells from the exponential or linear phases of the growth city exhibiting higher degrees of tolerance to the stresses. Fresh and dry weight accumulation in media with PEG were more rapid for Knox than for S. pennellii cells due primarily to major differences in the length of the lag phase of growth. The NaCl containing media, fresh and dry weight accumulation was slightly more rapid for Knox cells but S. pennelii cells grew to higher maxima. Both Knox and S. pennellii cells exhibited growth reductions in media with high levels of PEG or NaCl, manifested to the greatest extent by a reduction in maximum fresh weight gain. As is indicative by such reductions cell expansion was markedly reduced for cells growing in media with reduced water activities. The increase in tolerance observed in the exponential and linear phases of the growth cycle correlated well with the periods of maximum osmotic adjustment suggesting a relationship between turgor and tolerance as a function of the stage of growth. The growth reductions observed for both Knox and S. pennellii cells in media with PEG or NaCl was not a consequence of a lack of osmotic adjustment resulting in failure of turgor maintenance. The high degree of osmotic adjustment of S. pennellii cells compared to Knox cells was not correlated with the water stress and salinity tolerance differences which existed between the cells of the two genotypes. It was clear that S. pennellii cells required much higher turgor than did Knox cells in order to grow in media with or without PEG or NaCl. High osmotic adjustment and restricted expansion appear to be constituted properties of S. pennellii.
Degree
Ph.D.
Subject Area
Botany
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