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The effect of a droughting treatment on the polyribosome contentof wheat leaves was markedly different on leaves of differentages. Growing leaves showed a large decrease in their polyribosomepopulation, while fully expanded leaves showed no loss of polyribosomescompared with controls. These results suggest that the largereductions in polyribosome population observed in growing tissuesare due to reductions in growth, rather than a direct effectof water stress. 相似文献
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Cytochemical studies of esterase activity in 0.5 mm segmentsfrom root tips of Pisum sativum explanted for up to 9 days inbasal culture medium containing 2 per cent sucrose showed retentionof this activity. During this time, all segments from the secondand third 0.5 mm segments of the root tip developed xylem elementsas did the proximal end of the first segment. No xylem elementswere found in the 1214 cells behind the quiescent centre.It is concluded that the central group of meristem cells aregenerally programmed to form tissues of the stele immediatelyon leaving the quiescent centre, and that the programming forxylem and phloem elements occurs as a second step. Pisum sativum L., garden pea, determination, histochemistry, esterases, stele, root 相似文献