Characteristics of starch grains isolated from mature pepper leaves grown under different irradiances and daylengths
1989
Grange, R.I. | Hammond, J.B.W. | Andrews, J.
The size, shape and number of starch grains have been determined in mature pepper leaves taken from plants grown under defined conditions of daylength and irradiance. Starch grains were 0.2-7.0 micrometer diameter and 0.2-1.5 micrometer in thickness. Grain diameter was positively related to daylength and the number of grains per unit leaf area inversely related to daylength. Mean grain diameter was also positively related to leaf area. Analysis of starch grains from leaves having a wide range of starch contents showed that grain diameter was linearly related to leaf starch content. However, mean diameter only doubled with a 10-fold increase in starch content. The number of grains increased from approximately 5 X 10(10) m-2 of leaf to over 200 X 10(10) m-2 with increasing starch content. The total surface area of grains increased from less than 1.0 m2 m-2 leaf to over 20 m2 m-2 leaf. Leaf starch grain shape and size are compatible with both efficient storage as disc-shaped chloroplasts and the maintenance of high total grain surface area by increasing grain number more than diameter. Possible mechanisms for the control of grain initiation, growth and degradation are suggested.
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