Effects Of Light Environment Changes On Photosynthesis Of The Sporophyte And Gametophyte Of Pteris Vittata And Its Adaptation

Light is one of the most important environmental factors that affects the survival, growth and regeneration of plants, and also is a variable factor when habitats of plant or vegetation changes. Ferns are one of important groups of the plant kingdom, and the pioneer plant group in the proceeding of conquering the terrestrial environment. Ferns have two independent generations in their life history, the sporophyte and the gametophyte. They can survive separately on their own, but their morphology and habitats are very different form each other. Therefore, it is quite important to research the photosynthesis characteristics and the response mechanism to the light environmental change in the sporophyte and gametophyte of ferns.Pteris vittata is one kind of ferns living in high light surroundings. In this paper, the photosynthesis and adaptation to the light environment in the sporophyte and gametophyte of P. vittata after light change were studied in a laboratory condition.The results showed that:1. The chlorophyll fluorescence was detected in the geminating spores of P. vittata after germinated for 3 days. Significant differences of photosynthesis in the four development stages of P. vittata gametophyte were observed. While the gametophyte was developing, the photochemical efficiency of PSII (Fv/Fm), electron transfer rate(ETR), light capture ability(ΦPSII) and photochemical capacity(qP) was risen, and the heat dissipation(qN) was reduced. That demonstrated the photosynthetic capacity was enhanced during the development of gametophyte of P. vittata.2. The chlorophyll content, photochemical efficiency of PSII (Fv/Fm) of the shade leaves of P. vittata was reduced in full sunlight treatment, and the electron transfer rate(ETR), light capture ability(ΦPSII), photochemical capacity(qP) and LMA was significantly enhanced after adaptation to the high light.3. The chlorophyll content, photochemical efficiency of PSII (Fv/Fm) of the full sunlight leaves of P. vittata was reduced in the shade treatment, and the electron transfer rate(ETR), light capture ability(ΦPSII), photochemical capacity(qP) and LMA was significantly reduced in the shade. Constantly stayed in a low light condition, the sporophyte of P. vittata could survive by coming into new leaves, but suggested a decreasing photosynthesis and a low adaptation to the light environment change, which directly affected the growth of the fern. All of the photosynthesis characteristics of sporophyte and gametophyte reflected that P. vittata is a typical sun fern. Therefore, it is much more important that management planning and activities for conservation and resource use should take into account both habitat heterogeneity and biogeographic differences, which help maintaining the species diversity of forest vegetation.4. The photochemical efficiency of PSII (Fv/Fm), electron transfer rate(ETR), light capture ability(ΦPSII) and Photochemical capacity(qP) in the sporophyte of P. vittata were significantly higher than those of the gametophyte. It showed that the photosynthesis was significantly improved in the sporophyte than the gametophyte. Compared to the sporophyte, a strong light inhibition was found under the high light treatment of gametophyte of P. vittata. It illustrated that the adaptation to high light stress in the gametophyte is much lower than in the sporophyte. Light was essential to the germination of spores of P. vittata. But a high light intensity did not required in the growth of the gametophyte, which was appropriate for sporophyte. The increased photosynthetic capacity and the light adaptability of fern sporophyte played an important evolutive role for ferns to developing the terrestrial environment.