Study On The Photosynthetic Capacity Of Kosteletzkya Virginica(L.) Presl During The Growth And Development Of Leaf

Kosteletzkya virginica (L.) Presl is a newly introduced halophytes, in recentyears, more and more studies had been conducted on this plant，but less were carriedout on the leaves during the whole growth and development. To explore thephotosynthetic capacity in leaves of Kosteletzkya virginica (L.) Presl during thewhole growth and development, a combined measurement of basic physiologicalindex, gas exchange, chlorophyll fluorescence as well as chlorophyll fluorescencetransient were conducted. The main results are as follows:1. At the first three weeks, leaves expanded very quickly. The photosyntheticapparatus has been basically developed within four to five weeks along with the fullexpanding of leaves. During the development, the photosynthetic capacity increasedrapidly, and reached the peak before the biggest leaf area. Leaf chlorophyll,carotenoids, anthocyanins accumulated gradually, but decreased rapidly when leaveswere old. Leaf chlorophyll content was reduced after long time of salt treatment.2. During the growing process, the limiting factor of photosynthetic capacityhas experieced changes from non-stomatal factor to stomatal factor and thennon-stomatal factor again. Mature leaf has the highest ability to utilize light and CO2,while salt stress inhibited the ability to use strong light and low concentration ofCO2.3. The function of the PSII reaction center constantly optimized and has neverbeen damaged until the senescence of the leaves. It can be seen the fast fluorescenceparameters has no significant differences between control groups and the leaves aftersalt treatment,100mmol/L NaCl treatment did not much affect on acceptor side anddonor side of PSII.4. NPQ increased significantly in both old leaves and leaves under salt stress,which showed Xanthophyll cycle-dependent photoprotection played an important role in leaves of Kosteletzkya virginica (L.) Presl. The accumulation of carotenoidand anthocyanin in the leaf was conducived to consume excess energy. The ROSscavenging system was also very important.5.100mmol/L NaCl treatment shortened the leaf longevity by3weeks, andaccelerated the senescence of leaf. After long time treatment of salt stress, leaflength, leaf width and SOD activity were affected significantly while little influencewas found on other parameters. Salt treatment for a short time had little effect onphotosynthetic capacity, and some of the parameters were even higher. However,with the prolongation of treatment time, the effect of salt stress gradually showed up.6. From the results of this experiment it can be seen Kosteletzkya virginica (L.)Presl established adaptability to a low-salt environment. Leaves could grewnormally in100mmol/L NaCl environment though the vegetative period wasshortened. It is consistent with the growth status of the native coastal ones.7. Previous salt treatment study were mostlyconducted after two weeks of salttreatment, and the results (such as enzyme activity, photosynthetic parameters, etc.)were consistented with this experimental. However, the effect of salt stress on plantsvary with time. We propose to monitored the growth and physiologicalcharacteristics for a long period of time.