Study On The Growth And Physiological Characteristics Of Creeping Ramets Of Phragmites Australis Population In Alkali Habitat In Songnen Plain

As a typical clonal plant and cosmopolitan species,Phragmites australis has extensive ecological adaptability.In Songnen Plain,it is differentiated into several growth forms,which have obvious differences and relatively stable morphological and physiological characteristics in the long-term adaptation to the heterogeneous habitats.In bare alkali habitat,creeping ramets of P.australis population have the typical characteristics of "guerrilla" plants,also have their unique ecological characteristics,which is the result of long-term adaptation of P.australis population to the habitat.In this paper,by field observation and sampling in two years,a study on the creeping ramets of P.australis population was carried out in the bare alkaline extreme habitat,which was about the growth and physiological characteristics and the law of the distribution and integration of material,to provide scientific accumulation for the in-depth study of the ecological adaptation theory of clonal plants.The main results are as follows:?1?During the growing season,the elongation and growth of P.australis creeping ramets had unique ecological characteristics.In June,40 days after reviving,P.australis creeping ramets entered the vigorous growth period,which the elongation rate was significantly higher than that of the control group.The average elongation rate of the growing season was about 10 times higher than that of the control group,and the plasticity was greater.The time variation of total length was in accordance with logistic growth model.The elongation rate showed the process of change with slow firstly and then fast,at last slow.About sixty-fourth days after reviving,the elongation rate reached a maximum of about 16.22 cm/d.?2?The internode length of P.australis creeping ramets had a large plasticity,and its distribution had relatively stable ecological characteristics.At the end of the growing season,in 2015,the number of intenodes per plant was 9 to 39,with the average internode length of 3.77 cm.Most of the stolons produced 12 to 18 internodes,with the general total length of 36 to 56 cm,and the longest up to 364.30 cm;In 2016,the number of intenodes per plant was 13 to 60,and the average internode length was 6.09 cm.Most of the stolons produced 17 to 21 internodes,with the general total length of 52 to 68 cm,and the longest up 718.66 cm.In addition,it had nothing to do with the number of internodes,the distribution of internode length and the cumulative length of internodes had universal ecological characteristics.With the increase of internode sequence,the length of internodeshowed normal distribution,while the cumulative length showed logistic growth model,which indicated that the internodes in the middle sequence were the longest and the elongation rate was the largest,and the internodes at both ends were the shortest and the elongation rate was the smallest.?3?The quantitative characteristics of the spacer of P.australis creeping ramets had large plasticity and the spacer had a unique distribution pattern.In the two years,268 and205 spacers were obtained respectively,and their length distributions showed logarithmic normal distribution,with the general length of 6.24 25.7 cm and 10.12 56.43 cm,and the average spacer lengths were 12.12 cm and 28.93 cm.In 2016,the length of the spacer was more plastic.?4?The law of material distribution of P.australis creeping ramets had its unique ecological characteristics.During the whole growing season,the stems and leaves of the creeping ramets were allometry.The biomass ratio of stem in the two years was more than50%.The stem was the main contribution to population in both length and biomass.In addition,the number of basal ramets had little effect on the growth and development of the population,while the total biomass had a positive correlation with stem,leaf,ramet biomass and length,indicating that the P.australis population had a growth pattern of two modules both increasing.?5?The photosynthetic physiological characteristics of P.australis creeping ramet leaves were different from the other growth forms.The net photosynthetic rate,stomatal conductance and transpiration rate of the creeping ramet leaves showed the same trend with the increase of the age class,showing logistic growth model,which mature leaves and young leaves were significantly higher than that of aged leaves,while the intercellular CO₂ concentration had no significant difference but had opposite trend.It showed that mature leaves and young leaves had higher photosynthetic capacity,and they were the main position of material production.The photosynthetic physiological indexes of slanting basal ramets,erect basal ramets and nodes ramets leaves showed a quadratic curve variatio with the increase of the age class.It showed that the mature leaves were the main photosynthetic production part of the three growth forms.?6?N¹⁵isotopes have been physiologically integrated between P.australis ramets.The N¹⁵ natural abundance of the creeping ramets in the N¹⁵ isotope treatment group was significantly higher than that of the untreated control group.At the same time,the natural abundances of N¹⁵ between different organs and different parts were also different,which the average abundance of the lower stem reached 131.65‰,was significantly higher than the other parts,which indicated that the material was transported and transferred between the ramets which the basal ramets as "source" and creeping ramets as "sinks",and the integration had a transport direction that along the stolon to the top,with priority transportto the stem,followed by the leaf sheath,and finally the leaves.?7?In different years,the creeping ramets of P.australis showed a large ecological plasticity in morphology,physiology and so on.The differenecs of the internode length,ramet length,spacer length and the biomass of each module of the creeping ramets between the two years,were related to temperature and precipitation in the two growing seasons.It apparently showed that P.australis creeping ramets had strong adaptability to the environment.