Journal of Taiwan Agricultural Research

Author:Hsiu-Ying Lu*, Meng-Li Wei, Chun-Tang Lu and Lit-Fu Chan

Abstract:

    Productivity of corm is determined by the adequate growth of leaves in taro (Colocasia esculenta [L.] Schott). The development and growth of leaves vary with the environmental factors. The difference in rates of expansion of leaf surface can lead to the variation in leaf size and leaf shape. This study was to investigate the morphological changes occur in the taro leaves and examine the influence of climatic factors on the leaf size and leaf shape of taro during the growth periods. Binroshin taro and its improved cultivar “Kaohsiung No. 1” were used as materials. The experiments were conducted in two crop seasons at Taiwan Agricultural Research Institute. After leaf expanding, measurements were made every 2-4 days depending on the speed of plant development, until leaf is senescent and die. We used digit camera to capture images of the individual leaves and then used image measurement software to determine the image quantification. At harvest, fresh and dry matter weights for different fractions of each taro plant were measured. The principal components analysis showed the first component summarized size variation, while the second contrasted shapes. The shape component was determined by six indices together. Leaf shape of taro was appropriately described by determining the relative positions of the sinus base, the petiole-attaching point of leaf, the lobe tips to the apex, respectively, and the turning points of two lobe tips as well as the angle of sinus. The juvenile leaves were frequently narrower, longer and more lobed, but similar in their shape forms to mature leaves. The cultivar “Kaohsiung No. 1” had the greater right lobe, while Binroshin taro had the greater left lobe. Climatic factors influenced the leaf growth of taro. Rising temperature and higher solar radiation during the vigorous top-growth stage for January crop increased the rate of leaf expansion. This favored corm yield at maturity for January crop. On the other hand, declining temperature and lower solar radiation during the vigorous top-growth stage for July crop decreased the rate of leaf expansion. This resulted in poor yield at maturity. Planting times affected the growth patterns of the angle of sinus, and the ratio of length from the sinus base to the petiole-attaching point of leaf to maximum leaf length. The cultivar “Kaohsiung No. 1” grown in January had more rapid expansion in the ratio of length from the sinus base to the petiole-attaching point of leaf to maximum leaf length than that for the July crop and Binroshin taro. This resulted in greater leaf area, which in turn, favored corm yield at maturity.

Key words:Taro, Leaf size, Leaf shape, Principal components analysis, Image processing system, Climatic factor

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