The effects of CO2 concentration on spore germination, growth, and net photosynthetic rate (PN) of gametophytes of a tropical epiphytic fern, Pyrrosia piloselloides, were investigated over a 100-d period. Increasing CO2 concentration stimulated spore germination and enhanced gametophytic growth. The appearance of sexual organs and formation of sporophytes were accelerated with higher CO2 during growth. Radiant energy saturated PN and dark respiration rate also increased with increasing CO2 concentrations during growth. and Bee-Lian Ong, C. K-K. Koh, Yeow-Chin Wee.
Plants grown at low irradiance were fertilized with 0, 60, and 600 g m-3 NH4NO3 once every fortnight. Plants treated with high N concentrations showed an increased growth, producing longer and broader fronds with larger areas, and were darker green in colour. Nitrogen also increased the content of chlorophyll (Chl) and carotenoids per leaf area unit. Different N treatments did not affect the photosynthetic efficiency of photosystem 2, as reflected by the high values of Chl fluorescence kinetics Fv/Fm, ranging between 0.81 to 0.84, and Fv/F0 of 4.30 to 5.10. An increase in photochemical quenching (qP), accompanied by a decrease in non-photochemical quenching (qN), was observed in sporophytes fertilized with increased concentrations of NH4NO3. Nitrogen availability allowed sporophytes of Acrostichum aureum to become more established under natural conditions. and R. S. Pillai, B.-L. Ong.
Leaf mass per unit area (LMA), carbon and nitrogen contents, leaf construction cost, and photosynthetic capacity (Pmax) of Adiantum reniforme var. sinensis, an endangered fern endemic to the Three Gorges region in southwest China, were compared in five populations differing in habitat such as soil moisture and irradiance. The low soil moisture and high irradiance habitat population exhibited significantly higher LMA, area-based leaf construction (CCA), and carbon content (CA), but lower leaf nitrogen content per unit dry mass (NM) than the other habitat populations. The high soil moisture and low irradiance habitat populations had the lowest CCA, but their cost/benefic ratios of CCA/P max were similar to the medium soil moisture and irradiance habitat population due to their lower leaf Pmax. Hence A. reniforme var. sinensis prefers partially shaded, moist but well-drained, slope habitats. Due to human activities, however, its main habitats now are cliffs or steeply sloped bare rocks with poor and thin soil. The relatively high energy requirements and low photosynthetic capacity in these habitats could limit the capability of the species in extending population or interspecific competition and hence increase its endangerment. and J. X. Liao ... [et al.].
One broad-leaved pioneer tree, Alnus formosana, two broad-leaved understory shrubs, Ardisia crenata and Ardisia cornudentata, and four ferns with different light adaptation capabilities (ranked from high to low, Pyrrosia lingus, Asplenium antiquum, Diplazium donianum, Archangiopteris somai) were used to elucidate the light responses of photosynthetic rate and electron transport rate (ETR). Pot-grown materials received up to 3 levels of light intensity, i.e., 100%, 50% and 10% sunlight. Both gas exchange and chlorophyll (Chl) fluorescence were measured simultaneously by an equipment under constant temperature and 7 levels (0-2,000 μmol m-2 s-1) of photosynthetic photon flux density (PPFD). Plants adapted to-or acclimated to high light always had higher
light-saturation point and maximal photosynthetic rate. Even materials had a broad range of photosynthetic capacity [maximal photosynthetic rate ranging from 2 to 23 μmol(CO2) m-2 s-1], the ratio of ETR to gross photosynthetic rate (PG) was close for A. formosana and the 4 fern species when measured under constant temperature, but the PPFD varied. In addition, P. lingus and A. formosana grown under 100% sunlight and measured at different seasonal temperatures (15, 20, 25, and 30°C) showed increased ETR/P G ratio with increasing temperature and could be fitted by first- and second-order equations, respectively. With this equation, estimated and measured PG were closely correlated (r2 = 0.916 and r2 = 0.964 for P. lingus and A. formosana, respectively, p<0.001). These equations contain only the 2 easily obtained dynamic indicators, ETR and leaf temperature. Therefore, for some species with near ETR/PG ratio in differential levels of PPFD, these equations could be used to simulate dynamic variation of leaf scale photosynthetic rate under different temperature and PPFD conditions., S.-L.. Wong ... [et al.]., and Obsahuje bibliografii