Photosynthetic Characteristics of Two Semi-mangrove PlantsThespesia populnea andCerbera manghas
Thespesia populnea and Cerbera manghas, two semi-mangrove species with medicinal and ornamental values, play important roles in coastal ecosystems. In this paper, we examine the photosynthetic characteristics of the two species, including specific leaf areas, chlorophyll contents, chlorophyll fluorescence parameters, and photosynthesis-light response curves. Light saturation point (LSP) and light compensation point (LCP) ofT. populnea were 519.301 and 42.178μmol·m-2·s-1 respectively; and LSP and LCP ofC. manghaswere 268.287 and 29.862μmol·m-2·s-1 respectively. Therefore,T. populnea and C. manghas are typical heliophyte and mesophyte species.T. populnea had higher photochemical fluorescence quenching (NPQ, 2.264) and instantaneous water use efficiency (IWUE, 9.640μmol·mmol-1), indicating higher photo-protection and water use capacities in high-light conditions. When light intensity was higher than LSP, the photosynthetic rate ofT. populnea did not decline, suggesting stronger resilience to high-temperature and high-light intensity. With higher specific leaf area (SLA, 99.07 cm2·g-1) and chlorophyll a/b ratio (3.519)C. manghas could effectively absorb and transform light energy in low-light environments, thus could better adapt to low-light intensity environment. These results showed that in coastal zone greening,T. populnea can be a pioneer species, whileC. manghas could be cultivated with heliophyte plants or be planted at forest edges.
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