水田多年生雑草オモダカ繁殖体の生存状態と出芽に関する生態学的研究 : 第2報水田における出芽時期と繁殖体形成量との関係

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Studies on the growth and formation of propagules in an arrowhead (Sagittaria trifolia L.) were carried out when the mother tubers were planted from spring to autumn in paddy fields with and without standing crops during the normal and early season rice culture. The results obtained were as follows; 1) Leaves of the weeds under the rice canopy were adapted to weak light, and were broader and thinner than those under a single stand (Figure 1) . 2) Top dry weight of the plants between rice rows during the rice harvest season decreased with the delay in the time of planting of the tubers in both cropping seasons (Figures 2 and 3) . 3) Regrowth after rice harvest was observed in the early season culture regardless of the planting time (Figure 4) ,unlike in the normal season culture. 4) Correlation between maximum top dry weight and the number of tubers set was high. The number of tubers formed per plant between rice rows ranged from 0 to 40 in the normal season culture, whereas from 3 to 15 in the early season culture (Tables 1 and 2). 5) Top dry weight at the time of harvest of the plants which emerged later depended on the size of the mother tubers. The arrowhead plants which emerged from early to late July in the normal season culture grew more vigorously and set more propagules in the plot, where a vinyl chloride cylinder 200mm in diameter had been installed, for root protection than in the plots without this device (Figure 5) . 6) Achenes were produced in the plants which had emerged by early August in the fields without standing crops, whereas they were only formed in the plants which had emerged within a week after rice transplanting (late June) between the rows in the normal season culture(Figure 6) . 7) Few tubers were formed in the plants which had emerged after midseason drainage (early August) between the rice rows in the normal season rice culture (Figures 6 and 7) . 8) The results obtained suggest that the weed infestation may decrease in the normal season rice culture, if the weeds which have emerged by the time of midseason drainage could be controlled. Regrowth, however, and the formation of a large number of tubers may occur in the plants in the early season rice culture whenever emergence takes place. Thus, it is necessary to control the regrowth plants which appear after rice harvest in the fields in the early season culture.
1988-08-29

水田多年生雑草オモダカ繁殖体の生存状態と出芽に関する生態学的研究 : 第2報水田における出芽時期と繁殖体形成量との関係

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水田多年生雑草オモダカ繁殖体の生存状態と出芽に関する生態学的研究 : 第2報 水田における出芽時期と繁殖体形成量との関係

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水田多年生雑草オモダカ繁殖体の生存状態と出芽に関する生態学的研究 : 第2報水田における出芽時期と繁殖体形成量との関係