Adaptation to chilling stress in sorghum

McWilliam, J.R. and Manokaran, W. and Kipnis, T. (1979) Adaptation to chilling stress in sorghum. Other. New England University, Australia.

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A comparative study of the germination, early seedling development and chlorophyll synthesis of (a) Sorghum bicolor, (b) S. verticilliflorum (a tropical wild sp.), (c) S. leiocladum (a wild perennial growing in summer at 1000 m alt.) and (d) barley cv. Abyssinian at various temp. is presented. Initial germination, seedling respiration and mesocotyl extension declined as temp. was reduced from 24 to 8 deg C, with greatest and least effect in (c) and (d), resp. Arrhenius plots for all 3 responses were linear above and below a break at about 12 deg with differences less marked in (d) than in the sorghums. Slopes of regressions as measured by temp. coeff. (Q10) were greater in sorghums than in (d), especially below the transition temp. Very large increases in Q10 values below 12 deg in the most chill-sensitive spp. indicated very high activation energies and helped to explain poor germination and low growth rates at those temp. Storing imbibed seed of (a) at 8 deg for periods up to 20 days resulted in a small but insignificant delay in subsequent germination rate, whereas mesocotyl extension rates at favourable temp. were significantly reduced by previous storage of the germinated seedlings at 8 deg , suggesting that chilling stress had a more serious effect on actively growing than on dormant tissue. The amount of chlorophyll synthesized when etiolated (a) and (d) leaf tissue was exposed to various temp. in the range 8-26 deg for 24 h at 25 or 250 mu E/m2s decreased with decreasing temp., but (a) at 17 deg synthesized chlorophyll only at the lower irradiance level. Greening in (d) was not affected by irradiance down to 15 deg and was higher than in (a) at lower temp. It appeared from electron micrographs of (a) leaf tissue that the failure to develop chlorophyll at the higher irradiance was due to arrested development of plastid membrane systems which consisted largely of primary lamella layers with no evidence of grana development and that photo-oxidation of leaf pigments may prevent the development of a full functional grana and stroma thylakoid system. Similar results were obtained with 10 chill-sensitive and chill-resistant spp

Item Type: Monograph (Other)
Author Affiliation: Department of Agronomy, and Soil Sciences, New England University, Armidale, N.S.W., Australia 2351
Subjects: Plant Production
Plant Physiology and Biochemistry > Plant Physiology
Plant Physiology and Biochemistry > Biochemistry
Divisions: Sorghum
Depositing User: Ms K Syamalamba
Date Deposited: 02 Aug 2012 11:01
Last Modified: 02 Aug 2012 11:02

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