The Photosynthetic Physiological Characteristics On Phragmites Australis For Different Growth Forms In Bare Alkali Habitat In Songnen Plain

Photosynthesis is a most important physiological processes in plant growth, photosynthetic pigment including chlorophyll and carotenoid, leaf can absorbs and transfers light energy selectively so as to turn inorganic substance into organic matter. Phragmites australis is a widely distributed plant, with a strong ecological adaptability, it can become dominant species in bare alkali habitat in Songnen Plain and has several growth forms, in which the proportion of prone shape, sloping shape and upright shape are general larger, and the creeping shape is smaller. In this paper, based on the measured regularly, I studied the time and space dynamic of photosynthetic pigment content and photosynthetic physiological characteristics in different leaf age of three different growth forms of P. australis in bare alkali habitat, to provide scientific accumulation of exploring different growth forms of P. australis’ s adaptation strategies to environment. The main findings are as follows:(1) In different growth forms of P. australis, the leaves in the middle of plant had the highest photosynthetic pigment content, the content of chlorophyll a in prone shape in June, the lower part of the aging leaves(4-5a) and younger leaves of the upper level(7-9a) had no difference, but with stronger age(5-6a) in the middle part are difference significantly; in August, there was no difference between 7-12 a leaves, but it has significant difference with the older leaves; in mid-June, the sloping shape had significant difference between 4 and 7 age leaves; in August, between 6 and 10 age had significant difference; upright shape only difference between the middle of the stronger age leaves(4-5a) and 3 age in mid-June was significant; August, only the lower part of the aging stage(4-5a) and the upper leaves of stronger age difference(7-12a) significant; there was no significant difference in each leaf age of three growth forms in July. The spatial variability and difference of indicators of chlorophyll b of three growth forms were generally similar to chlorophyll a.(2) The photosynthetic pigment content of the same leaf in different growth forms changes consistency in different sampling times. About the Chlorophyll a content, 4a and 5a of prone shape had significant difference in the early and vigorous growing season, 6-9a significantly different in the vigorous growing season, 10 a had no significant differences in each growing period; sloping shape’s 5-8a had significant difference between the early growing season and vigorous growing season, 9-11 a in various growing periods were not significant; the 3a of upright shape had significant difference between the early growing season and vigorous growing season, 4-7a leaves were significantly different between earlier and later growing period, 8-11 a did not reach significant level in each period. In a word, time variation of chlorophyll b content, total chlorophyll and carotenoid content of three growth forms are generally similar to the chlorophyll a.(3) In different leaf age in three growth forms of P. australis,the space variation of photosynthetic physiological characteristic were not same. Net photosynthetic rate in prone shape had no difference in each leaf age in June and July; in August, there was no significant difference among 7-13 a leaves which were in the upper part, but it was different from older leaves(5-6a) in the lower part; sloping shape only had significant difference between the leaves(5-9a) in the middle or upper part and older leaf(4a) in end of June; in upright shape, the highest one was the leaf(9-13a) in the middle in July, and difference among every leaf age was significantly. The time variation and the difference of stomatal conductance, transpiration rate and intercellular CO2 concentration of three growth forms were generally similar to net photosynthetic rate.(4) The photosynthetic physiological characteristic of different growth forms changes consistency in different sampling times. Among them, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration in every leaf age were highest in early July, and transpiration rate generally highest in late June in prone shape, sloping shape common to mid-July, upright shape generally highest in mid-June; physiological characteristics were commonly lowest in early or mid-August, and the difference between them were significant partly.(5) In different growth forms of P. australis, photosynthetic pigment content and photosynthetic physiological indexes in different leaf age had consistent regular pattern by reducing after the first increase of conic in different times. The peak appeared all in the middle leaf age. Among them, the highest net photosynthetic rates of prone shape were 6a, 9a and 10 a, and sloping shape were 7a, 7a and 9a respectively; upright shape were 6a, 9a and 10 a respectively in late June, early July and late July; the laws of stomatal conductance, intercellular CO2 concentration and transpiration rate were similar to net photosynthetic rate. It reflected that with the continue growth and development of plants, leaves which had stronger production capacity during photosynthesis constantly moving up orderly with the increased by the number of leaves.(6) Photosynthetic physiological characteristics of P. australis in three growth forms totally performance for prone shape was taller, and photosynthetic pigments content were significantly higher than sloping shape and upright shape which are dwarf in the early growing season; in the mid-growing season, three forms remained fairly level; but in the late-growing season, photosynthetic pigment content of upright shape were significantly higher than prone shape and sloping shape. It is possible relevant to the earlier reviving of prone shape and sloping shape from dormancy, and the upright shape can maintain strong growth for a long time.(7) The photosynthetic pigment content and photosynthetic indexes of P. australis leaves in two years, the carotenoid was significantly higher in 2014 than the same period in 2013, and chlorophyll a, chlorophyll b, carotenoids, total chlorophyll content and net photosynthetic rate, stomatal conductance and transpiration rate, basically performed that higher in 2013, this may related to the temperature, precipitation and other environmental factors in two growing season, it also reflected that the plant’s adaptation to the environment. The complementary relationship between carotenoid and chlorophyll is the result of long-term evolution of the photosynthetic physiological characteristics.