Journal of Taiwan Agricultural Research

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

Abstract:

    Corms of wetland taro (Colocasia esculenta (L.) Schott) were planted in the most favorable (January) and less favorable (July) cropping seasons in the year 1995 and 1996 in Taiwan. Plants were randomly samples at one-month interval from planting to harvest (the 8^th months after planting). Data of dry weight, total nitrogen (N) and total nonstructural carbohydrates (TNC) concentration in different plant fractions was analyzed. The purpose of this study was to understand the causes of yield difference due to seasonal factors and to find out the major limited factors for low yield. It was detected that leaf contained the highest N concentration while corm contained the highest TNC concentration during the whole growth period for both cropping seasons. It was also found that petiole had the capability of storing carbohydrates. The dry weight of corm was higher on January planted plants than July planted plants for both two years. It was assumed that high temperature and high solar radiation during plants vigorous top-growth stage for January planted plants increased the capability of dry matter production in the aboveground vegetative organs along with higher amount of nitrogen transferring to the corm. Similarly, the contribution of TNC to corm hulking was found also high on January planted plants. The maximum possible contribution of total stored TNC to corm TNC at the corm rapid-bulking stage were up to 13~19 % on January planted plants when the respiratory consumption was not considered. In conclusion, all the factors for higher photosynthetic production may result in the higher yield on January planted plants. On the other hands, declining temperature, solar radiation and shorter photoperiod caused poor photosynthetic production during vigorous top-growth stage in the aboveground vegetative organs. Therefore the less photosynthetic production transferring to the corm during vigorous top-growth stage may conduct to main cause of lower yield for July planted plants. It was thought that the production of dry matter and carbohydrates during the vigorous growth stage was not enough to meet the demanding for rapid corm hulking since the partition of total dry weight, N and TNC in corm has not significantly increased during the 6th months after planting to the harvest.

Key words:Taro, Planting season, Dry matter, Nitrogen, Total nonstructural carbohydrates

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