| Abstrakt: |
Air temperature regulates the photosynthesis and growth of mangrove plants, but the effect of soil (root-zone) temperature is unclear. To clarify the mechanisms underlying change in mangrove growth in relation to soil temperature, we examined how root-zone cooling inhibited the photosynthesis and growth of Kandelia obovata Sheue, H.Y. Liu & J. Yong, which is a relatively cold-tolerant mangrove species. We collected K. obovata propagules in a subtropical region and planted them in sand-filled pots in a glasshouse. The seedlings were divided into two groups, with soils completely submerged in 20°C or 30°C water. The relative growth rate of K. obovata seedlings was lower at a soil temperature of 20°C than of 30°C, and K. obovata leaves had significantly lower maximum carboxylation rates (Vcmax) at a soil temperature of 20°C than of 30°C. Vcmax was significantly positively correlated with the leaf NO3–N content, root length, and leaf sugar and starch contents, suggesting that the carboxylation capacity of K. obovata was regulated by inorganic nitrogen availability rather than by negative feedback regulation associated with end-product accumulation. Our results suggest that the growth and photosynthesis of mangrove species in a subtropical region are reduced not only by low air temperature, but also by low soil temperature. These findings partly support the hypothesis that the distribution of mangrove plants is affected by sea surface temperature (which affects the soil temperature), and that their latitudinal limits often coincide with a winter sea surface temperature of 20°C. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink