Stomatal density of sago palm (Metroxylon sagu Rottb.) with special reference to positional differences in leaflets and leaves, and change by palm age

Abstract

 This study was undertaken to investigate the stomatal density in leaflets of sago palm, a tropical starch crop, to gain some fundamental knowledge related to photosynthesis of the leaves. 1) To investigate the Stomatal density at different parts on leaflets attached to lower, middle and upper positions in one leaf, leaves on the lower, middle and upper parts of plants were sampled from the palms at trunk formation stage (about 5-years old) in a farmer’s sago garden in Tebingtinggi Island in Riau, Indonesia. The tip part of a leaflet had lower stomatal density than basal or middle part, and abaxial surface had higher stomatal density (550-750/mm²) than adaxial surface (100-250/mm²)．Stomatal density of both sides on a leaflet showed a tendency to decrease from base to tip part with the decrease in thickness. Little difference was observed in the stomatal densities among leaves and leaflets at different positions in a plant and in one leaf, respectively. 2) To investigate the change of stomatal density by palm age, leaflets on the middle position in leaves of middle part of 1- to 5-years old palms were sampled in a farmer’s sago garden in Muka, Sarawak, Malaysia. stomatal density of abaxial surface markedly increased from 1- to 3- years old (400-900/mm²)，however, it gradually increased thereafter and attained almost the definite value (1000/mm²) at 5-years old, trunk formation stage. In adaxial surface, the stomatal density also increased with aging of palms, but the density (50-120/mm²) is significantly smaller than that of abaxial surface (400-1000/mm²)，irrespective of palm age.