Manipulation of light and CO(2) environments of the primary leaves of bean (Phaseolus vulgaris L.) affects photosynthesis in both the primary and the first trifoliate leaves: involvement of systemic regulation

摘要

Possible involvement of systemic regulation of the photosynthetic properties of young leaves by the local environments and/or photosynthate production of the mature leaves were examined using Phaseolus vulgaris plants. When primary leaves (PLs) were treated with air containing 150 microL CO(2) L(-1) with the other plant parts in ambient air at a photosynthetic photon flux density (PPFD) of 300 micromol photon m(-2) s(-1), decreases in the photosynthetic rate measured at 360 microL CO(2) L(-1) and a PPFD of 300 micromol photon m(-2) s(-1) (A(360)) were markedly retarded in both PLs and the first trifoliate leaves (TLs) as compared to plants treated with 400 microL CO(2) L(-1). Conversely, when PLs were treated with 1000 microL CO(2) L(-1), decreases in A(360) were accelerated in both PLs and TLs. Shading of PLs accelerated the decrease in PL A(360), and delayed the decrease in TLs. In the CO(2) treatments, changes in A(360) in TLs were mainly attributed to the changes in ribulose bisphosphate (RuBP) carboxylation rate, while the shading of PLs caused increases in both the RuBP carboxylation and regeneration rates in TLs. The ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity on chlorophyll basis, an indicator of sun/shade acclimation, differed both among PLs and among TLs in accordance with the redox state of photosystem II (PSII) in PLs. Although carbohydrate contents of TLs were not affected by any manipulation of PLs, changes in the photosynthetic capacities of TLs acted to compensate for changes in PL photosynthesis. These results clearly indicate that the CO(2) and shade treatments of PLs not only affect photosynthetic properties of the PLs themselves, but also systemically affected the photosynthetic properties of TLs. Possible roles of the redox state and photosynthate concentration in PLs in regulation of photosynthesis in PLs and TLs are discussed.