Differential Responsiveness in Zonal Growth of Cocklebur Seed Axes to Co_2, C_2H_4, O_2 and Respiration Inhibitors

概要

論文の詳細を見る
The axial growth of de-coated cocklebur (Xanthium pennsylvanicum Wallr.) seeds, whose axes were divided into 4 zones, was examined in relation to the temperature-dependent shift of the effect of C_2H_4 on germination. At 23℃, where both C_2H_4 and CO_2 stimulated germination, CO_2 promoted the axial growth at the radicle tip zone, whereas C_2H_4 promoted growth in the proximal portion of the axis. At 33℃, C_2H_4 inhibited germination, and strongly suppressed the growth at the radicle tip, whereas the effect of CO_2 did not change. The inhibition of growth at the radicle tip zone was alleviated by O_2 enrichment, which also reversed the inhibition of germination. It is thus apparent that the temperature-dependent shift of the action of C_2H_4 is associated with a temperature-dependent responsiveness of the radicle tip zone to C_2H_4. Growth of the radicle tip zone was sensitive to NaN_3, whereas the proximal portion was sensitive to benzohydroxamic acid, an inhibitor of alternative respiration, suggesting that there may be an increase in the operation of the alternative respiration path along a gradient of axial tissue from the tip towards the cotyledonary side. The effects of CO_2 and C_2H_4 are discussed in relation to the different respiratory activities in each axial zone of cocklebur seeds.