Photosynthesis, respiration, and growth patterns of Rhizophora stylosa seedlings in relation to growth temperature

Key message: Rhizophora stylosa Griff. exhibits thermal acclimatization of leaf respiration, but does not maintain high photosynthetic performance under new growth temperatures. Abstract: Mangrove plants are distributed across the majority of the world’s tropical and subtropical coastlines. How they respond to new growth temperatures is poorly understood. To obtain this information, we collected Rhizophora stylosa Griff. diaspores from a subtropical region with average daily mean and maximum temperatures of 24.0 and 26.7 °C. After 1-year-old seedlings had been grown in four glasshouse chambers at an air temperature of 15, 20, 25, or 30 °C for about 50 days, we evaluated photosynthesis, respiration, and growth. Seedlings grown at 15 and 20 °C showed PSII photoinhibition, especially in newly emerged leaves. The assimilation rate was greatest at 25 °C. Thermal acclimatization of respiration was observed at 20–30 °C in both newly emerged and pre-existing leaves, was unclear in stems, and was absent in roots. Stem growth rate was greatest at 25 °C, but seedlings grown at 30 °C produced the largest number of new leaves and marginally decreased biomass allocation to roots, which lacked thermal acclimatization capacity. These results indicate that R. stylosa growing in subtropical regions adapts its photosynthesis to the average daily mean or maximum temperatures, and minimizes carbon loss due to warm temperatures by use of the thermal acclimatization capacity of leaf respiration and plasticity of biomass allocation, which contribute to optimizing growth performance.