Genotypic, intraplant, and environmental variation in stomatal frequency and size in wheat

Abstract

Stomatal characteristics are of interest in physiological studies and in the development of cultivars to improve productivity or stress resistance. In wheat (Triticum spp.) previous studies show contradictory results for intraplant variation in stomatal frequency and size. Our objective was to investigate the effects of genotype, environment and intraplant variation on stomatal frequency, size and the total stomatal area per unit leaf area in tetraploid (T. turgidum L. var. durum) and hexaploid (T. aestivum L.) wheat, and to assess requirements of sample size and allocation for determining genotypic differences. Significant variation was found in stomatal frequency within leaves (position on leaf and between surfaces), among leaf positions within plants, and with leafage in both wheat species. To obtain consistent genotypic differences, fully expanded leaves from the same plant position should be taken, and frequency counts should be made on the same leaf surface and at a constant position within leaves. Although stomatal frequency was negatively correlated with stomatal size, the total stomatal area per unit leaf area usually increased with increasing stomatal frequency. Stomatal frequency increased under dry or high light intensity environments. There were no significant changes in genotype rank order for stomatal frequency in different environments. Increasing the number of leaves sampled had a greater impact on precision of determination of stomatal frequency than increasing the number of microscope fields counted within leaves. Key words: Stomata, Triticum aestivum L., T. turgidum L. var. durum