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滩涂消浪林是中国沿海防护林体系的前沿阵地,在防浪促淤、保岸护堤和防御海洋自然灾害等方面具有重要的作用。以中亚热带泥质海岸的两种消浪树种海滨木槿(Hibiscus hamabo)和蜡杨梅(Myrica cerifera)一年生幼苗为实验材料,根据半日潮滩涂的淹水时间和淹水深度,设计5种实验处理,即在每个半日潮中,两个树种的平均淹水时间和淹水深度分别为1 h和15 cm(处理1)、2 h和25 cm(处理2)、3 h和35 cm(处理3)、4 h和45 cm(处理4)以及无水淹的对照处理(用淡水正常浇灌)。在模拟海水水淹胁迫下的70 d中,研究两树种幼苗向阳面叶片的光合作用日变化及其与叶片其他生理生态因子的关系,揭示其主要影响因子。结果表明,各处理下,海滨木槿幼苗叶片净光合速率(Pn)日变化(6︰00~18︰00)曲线为单峰曲线;在水深较浅、时间较短的水淹处理下,海滨木槿幼苗叶片Pn主要受光合有效辐射(PAR)影响,在水深较深、时间较长的水淹处理下,则主要受叶片气孔导度(Gs)和胞间CO2浓度(Ci)的影响;在水淹初、中期,蜡杨梅幼苗叶片Pn日变化曲线为双峰曲线,但在水淹后期,其为单峰曲线;在水深较浅、时间较短的水淹处理下,蜡杨梅幼苗叶片Pn主要受PAR和Gs影响,而在水深较深、时间较长的水淹处理下,其主要受Ci和饱和水蒸汽压亏缺影响。
Tidal flat is the forefront of the coastal shelter forest system in China, and plays an important role in preventing siltation, preserving the bank and protecting the marine natural disasters. Taking Hibiscus hamabo and Myrica cerifera annual seedlings as test materials, two kinds of surf-breaking shrub species in the subtropical muddy coast were used as experimental materials. According to the flooding time and the depth of flooding, That is, the average flooding time and flooding depth of the two species were 1 h and 15 cm (treatment 1), 2 h and 25 cm (treatment 2), 3 h and 35 cm (treatment 3 ), 4 h and 45 cm (treatment 4) and no flooded control (normal watering with freshwater). The diurnal variation of photosynthesis and its relationship with other physiological and ecological factors in leaves of sunlit leaves of two tree species were studied during the 70 days simulated by seawater flooding to reveal the main influencing factors. The results showed that the curve of net photosynthetic rate (Pn) diurnal variation (6︰00 ~ 18︰00) of Hibiscus makinoi seedlings under each treatment was a single peak curve. Under the condition of shallow water depth and short time flooding, Pn of seedling leaves was mainly affected by photosynthetically active radiation (PAR). Under deeper and longer flooding treatments, Pn was mainly affected by leaf stomatal conductance (Gs) and intercellular CO2 concentration (Ci) The diurnal variation curve of Pn in leaves of A. waxya seedlings was bimodal at the beginning and the middle of flooding, but it was a single-peak curve at the later period of flooding. Under the condition of shallow water depth and short flooding, Affected by PAR and Gs, under deep and prolonged flooding, it is mainly affected by Ci and saturated water vapor pressure deficit.