Anatomy of chlorenchyma cells in maize lines developed at different latitudes and grown at sub- and supraoptimal temperatures

Three inbred lines of maize ( Zea mays L.) from cool temperate regions and three from warm regions were grown at 14, 22, 30 and 38°C up to the same physiological age, the full expansion of the third leaf. The laminae of the second leaf were studied for anatomical traits of the chlorenchyma. The genotypic variation was considerable for all properties. Nevertheless, general temperature response curves existed for many properties with few deviations of single lines. The cross-sectional area of mesophyll cells and cross-sectional area and number of chloroplasts declined from 14 to 22°C, increased up to 30°C and declined again up to 38°C. The ratio of shortest to longest diameter of chloroplasts was low in mesophyll cells at intermediate temperatures, and maximum in bundle sheath cells at 30°C. Temperature response curves for other properties of the bundle sheath cells were predominantly genotype specific. Chloroplasts in bundle sheath cells were sometimes smaller than those of mesophyll cells, dependent on temperature and genotype. Values of lines from cool temperate and warm regions were mostly overlapping, but the cross-sectional area of mesophyll cells was larger in the latter than in the former lines at low temperature. The results are discussed in relation to the expression of photosynthetic properties.