Morpho-anatomical adaptation of lesser yam (Dioscorea esculenta) on different planting pattern and relative light intensity in Java community forest

Abstract

Lesser yam (Dioscorea esculenta) is traditionally cultivated as a valuable crop species in a various planting pattern of teak-based agroforestry (AF) system in Watubonang village, Sukoharjo District, Central Java. Different planting pattern contributes to various light intensity which is associated with plant morphological and anatomical changes and directly affect to yam tuber production. Research site was selected by mean of purposive sampling method with three yam planting patterns, i.e. yam monoculture (Y), yam in trees along border (TAB) and yam in full teak trees (T-Y), in three replicates of 20 m x 20 m plots. In each plot, four subplots were established to investigate relative light intensity and take leaf samples. Changes in morphological and anatomical characteristics of yam to different planting pattern and relative light intensity (RLI) were studied, including leaf size, leaf color, tendril and internode length, chlorophyll content and stomatal density. The result showed that RLI were significantly different among planting pattern (Y: 78.66%, TAB: 66.94%, T-Y: 34.05%). Planting pattern and interaction between planting pattern and RLI significantly affected yam morphological and anatomical characteristics (of leaf size, tendril & internode length, and stomatal density) at P < 0.05. Leaf size, tendril and internode length increased with decreasing of RLI in TAB, but opposite adaptation was found in T-Y planting pattern. Higher RLI resulted in reductions of chlorophyll a and chlorophyll b content, and therefore increased of chlorophyll a:b ratio. Leaf color of yam grown under high RLI (Y) were light green, while those grown under shaded condition with relatively low light intensity (TAB, T-Y) were dark green that may related to the foliar chlorophyll content. Hence, a trend of decreasing stomatal density was found associated with lower RLI (Y: 35 stomatal/mm2, TAB: 25 stomatal/mm2, T-Y: 19 stomatal/mm2). Approximately 50-60% of RLI is suggested to be an optimum intensity for yam cultivation to support yam tuber production. Agroforestry practice by applying pruning and managing planting density are needed to reach the optimum light.