Stomatal Characteristics at Different Ploidy Levels inCoffeaL.

Stomatal frequency, epidermal cell frequency, stomatal guardcell length and stomatal index were examined at different ploidylevels inCoffea. In general, stomatal and epidermal cell frequencyper unit leaf area decreased while stomatal guard cell lengthincreased with an increase in ploidy. The reduction in stomatalfrequency at higher ploidy levels was mainly a result of largerepidermal cells. In the case ofC. canephora(cultivar S.274)a significant reduction in stomatal frequency was noticed fromdiploid to tetraploid level which was due to both larger epidermalcell size and less stomatal differentiation at the tetraploidlevel. Besides the effect of ploidy on stomatal frequency andguard cell length, genotypic differences in stomatal frequencyand stomatal guard cell length were also observed among cultivarsof the same ploidy level. Although variation in stomatal frequencyamong cultivars was found to be associated with the differencein stomatal to epidermal cell ratio, variation in guard celllength was attributed to differential genetic architecture.In the present study a highly significant positive correlation(r=0.82) between stomatal and epidermal cell frequency and highnegative correlations between stomatal frequency and guard celllength (r=-0.91) and epidermal cell frequency and stomatal guardcell length (r=-0.93) were obtained. The study also indicatedthat stomatal frequency can be predicted with 83 and 87% accuracy,respectively, by measuring stomatal guard cell length in coffee.Copyright1997 Annals of Botany Company Coffea; ploidy level; stomatal characteristics