Showing papers in "Plant and Cell Physiology in 1983"

Auxin-induced changes in the cell wall xyloglucans: Effects of auxin on the two different subtractions of xyloglucans in the epicotyl cell wall of vigna angularis

Abstract: In order to study the IAA-induced modifications of the cell wall of azuki bean {Vigna angularis Ohwi et Ohashi cv. Takara) epicotyl segments, the xyloglucans were subfractionated into two components, i.e., 4K-U and 24K xyloglucans, which were obtained by extraction with 4% KOH solution containing 8 M urea and 24% KOH solution, respectively. The weight-average molecular weights of 4K.-U and 24K xyloglucans were estimated to be 40 x 10 and 106 x 10, respectively. Complete acid hydrolysis of 4K-U and 24K xyloglucans gave glucose, xylose, galactose and fucose in mole % 48.3 : 33.5 : 13.8 :4.4 and 45.3 : 30.9 : 19.6 : 4.3, respectively. Treatment of epicotyl segments with IAA (0.1 miu) caused a decrease in the amount of 24K xyloglucans and an increase in 4K-U xyloglucans, whereas the total amount of the two xyloglucans remained constant. Furthermore, TAA treatment caused a decrease in the molecular weight of 24K xyloglucans from 106X 10 to 78 X 10 without causing changes in their sugar compositions. With 4K-U xyloglucans, IAA caused an increase in the mole % of xylose and a decrease in the mole % of galactose and fucose.

Differentiation of Photorespiratory Activity between Mesophyll and Bundle Sheath Cells of C4 Plants I. Glycine Oxidation by Mitochondria

Abstract: Mitochondria were isolated from mesophyll protoplasts and bundle sheath protoplasts or strands which were obtained by enzymatic digestion of six C4 species: Zea mays, Sorghum bicolor, Panicum miliaceum, Panicum capillare, Panicum maximum and Chloris gayana, representative of three C4 types. Photorespiratory glycine oxidation and related enzyme activities of mesophyll and bundle sheath mitochondria were compared. Mesophyll mitochondria showed good P/O ratios with malate and succinate as substrate but lacked the ability to oxidize glycine. On the other hand, mitochondria isolated from bundle sheath protoplasts of P. miliaceum and bundle sheath strands of Z. mays possessed glycine oxidation activity similar to that of mitochondria from C3 plant leaves. The two enzymes involved in glycine metabolism in mitochondria, serine hydroxymethyltransferase and glycine decarboxylase, were also assayed in the mitochondria of the two cell types. The activities of the two enzymes in bundle sheath mitochondria were in the range found in C3 mitochondria. In contrast, the activities in mesophyll mitochondria were either not detectable or far lower than those in bundle sheath mitochondria and ascribed to contaminating bundle sheath mitochondria. The present results indicate the deficiency of a complete glycine oxidation system in mesophyll mitochondria and also a differentiation between mesophyll and bundle sheath cells of C4 plants with respect to the photorespiratory activities of the mitochondria.

Changes in Microtubules in Onion Leaf Sheath Cells during Bulb Development

Abstract: Cortical microtubules are oriented transversely to the cell axis in leaf sheath cells of onion plants (Allium cepa L. cv. Osaka-Okute) that have not started bulb formation. As the bulb develops and the leaf sheath cells swell, the microtubules become disoriented and scattered and finally disappear. The microtubule inhibitors colchicine and cremart [O-ethyl O-(3-methyl-6-nitrophenyl)N-i«c-butylphosphorothioamidate] cause swelling of leaf sheath cells and make the basal part of the plant bulbous. The cortical microtubules may have an important role in regulating bulb development in onion plants.