Identification of Arabidopsis thaliana haploid plants by counting the chloroplast numbers in stomatal guard cells

Production of haploid plants constitutes an invaluable tool in basic plant biology and plant breeding. In Arabidopsis thaliana, haploids can be obtained by a simple in vivo method based on manipulation of the CENH3 (Centromere specific histone H3) gene. Haploid Arabidopsis thaliana plants can be distinguished from the diploid counterparts by morphological, cytological, genetic and molecular methods. In this present study, as an alternative to morphological identification, we compared the number of chloroplasts in stomatal guard cells, size of stomatal guard cells in haploid and diploid A. thaliana to develop an easy method to identify haploids. The number of chloroplasts in stomatal guard cells were reduced to almost half in haploids. Similarly, the size of stomatal guard cells was also reduced in haploids. Therefore counting the number of chloroplasts in stomatal guard cells can be used as a diagnostic method to distinguish haploid from diploid. Chloroplast and stomata numbers directly affect the rate of photosynthesis and transpiration. Hence, A. thaliana haploids may also be a valuable tool to study the effect of genome size on plant physiological and biochemical processes.