Phenotypic Analysis And Physiological Study Of Lowland Octoploid Panicum Virgatum L.

Panicum virgatum L.is a perennial herbaceous C₄ plant native to North America.In this study,the tetraploid low-land switchgrass species Alamo?4-1?was used as the research material,and the callus induced was treated with colchicine.A high-efficiency chromosome doubling system of switchgrass was established by tissue culture,and ploidy of three tetraploid low-land switchgrass varieties Alamo?4-1?,Kanlow?83-2?and Newyork?84-1?were evaluated.The phenotypes of the three lowland switchgrass octaploid plants were systematically evaluated by field experiment,and their photosynthetic physiology and salt tolerance physiology were analyzed.The main findings are as follows:?1?The callus was induced by immature spike from the lowland tetraploid switchgrass Alamo?4-1?,and the callus was treated with 0.1%colchicine for 0 d,2 d,3 d,5 d and7 respectively.Results showed that the treatmentwith 3 d had the highest induction rate which was as high as 48.7%.The ploidy of three tetraploid lowland switchgrass cultivars was identified by stomatal morphology and flow cytometry.The results showed that the number of stomata in octoploid leaves within one unit of viewwas significantly less than that of tetraploid,but stomata size in octoploid was ignificantly larger.Flow cytometry identification showed that the relative DNA content of octoploid was about twice that of tetraploid.?2?Phenotypic analysis of low-land octoploid switchgrass.The octoploids and tetraploid controls of three low-land type switchgrass varieties planted in the field for2 years were used as research materials.Agronomic traits such as plant height,tiller,stem diameter and leaves of octoploid lowland switchgrass were systematically analyzed.And results showed that the plant height and tillers of octoploid and tetraploid of three switchgrass varieties increased gradually during different growth periods.Among them,the plant grew faster at the beginning of July,and gradually stabilized in mid-August;the tiller reached the first peak in mid-August,and reached the second peak when the growth stopped in autumn;The trend line of plant height and tillering of three tetraploid switchgrass varieties was higherthan that of octaploid.Compared with the tetraploids,the plant height,the tiller and fresh weight were reduced significantly in their octaploids,while the pollen size and single tiller weight increased.?3?Analysis of photosynthetic physiological differences betweenoctaploids and their tetraploid control in three lowland switchgrass varieties.Compared with the tetraploid control,the net photosynthetic rate,intercellular CO₂ concentration,transpiration rate and stomatal conductance of the three lowland switchgrass octaploids increased significantly.Further analysis of the leaf structure showed the ovulation of mesophyll cells switchgrass increased,the mesophyll cells arranged closely,the number of chloroplasts and chlorophyll content increased significantly,and the vascular bundle sheath of the leaves increased significantly in octaploids of the three switchgrass varieties.?4?The seed characteristics of octaploids and their tetraploid control were compared in the three lowland switchgrass varieties s.Compared with the tetraploid control,the seed size and 1000-grain weight of octoploids increased significantly.The seed germination rate,seedling bud length,root length and fresh weight of three lowlandoctaploid switchgrass and its tetraploid control in different salt solutions?0,60,120 and 180 mmol/L NaCl?were determined.The results showed that salt tolerance of Alamo seeds was the best;further studies were conducted treated with different salt solutions?0,100,200 mmol/L NaCl?at the seedling stage,and results showed that the cell membrane permeability of leaves was lower in octaploids than that in tetraploid control,while the chlorophyll content,proline content,antioxidant enzyme activity,etc.were significantly enhanced,which suggested the salt tolerance of octaploids was enhanced.