STOMATAL CHARACTERISTICS AT DIFFERENT PLOIDY LEVELS IN COFFEA L

Stomatal frequency, epidermal cell frequency, stomatal guard cell leng th and stomatal index were examined at different ploidy levels in Coff ea. In general, stomatal and epidermal cell frequency per unit leaf ar ea decreased while stomatal guard cell length increased with an increa se in ploidy. The reduction in stomatal frequency at higher ploidy lev els was mainly a result of larger epidermal cells. In the case of C. c anephora (cultivar S.274) a significant reduction in stomatal frequenc y was noticed from diploid to tetraploid level which was due to both l arger epidermal cell size and less stomatal differentiation at the tet raploid level. Besides the effect of ploidy on stomatal frequency and guard cell length, genotypic differences in stomatal frequency and sto matal guard cell length were also observed among cultivars of the same ploidy level. Although variation in stomatal frequency among cultivar s was found to be associated with the difference in stomatal to epider mal cell ratio, variation in guard cell length was attributed to diffe rential genetic architecture. In the present study a highly significan t positive correlation (r = 0.82) between stomatal and epidermal cell frequency and high negative correlations between stomatal frequency an d guard cell length (r = -0.91) and epidermal cell frequency and stoma tal guard cell length (r = -0.93) were obtained. The study also indica ted that stomatal frequency can be predicted with 83 and 87% accuracy, respectively, by measuring stomatal guard cell length in coffee. (C) 1997 Annals of Botany Company.