Responses Of Biological Characteristics Of Different Barnyard Grass To Different Photoperiod Treatments

As a new type of high-quality forage grass for the development of green livestock products,Echinochloa can be reasonably grown to obtain a large and stable amount of forage fodder,which is beneficial to the development of regional livestock industry.Photoperiod,as one of the key ecological factors regulating plant growth,development and nutritional quality,can directly influence the growth and development of crops,and thus regulate their yield and quality.Therefore,it is of great scientific significance to investigate the mechanism of different photoperiods on plant growth and development and their regulation to predict and guide crop introduction and high-yield cultivation.Based on this,we used Echinochloa crusgalli(L.)Beauv.var.mitis(Pursh)Peterm.’Ningxia’,Echinochloa frumentacea(Roxb.)Link and Echinochloa crusgalli(L.)Beauv.crusgalli(L.)Beauv.’Chaomu 1’ were subjected to different photoperiodic treatments in the artificial climate chamber,with five treatments and three replications for each treatment,8 h/16 h(Ph8),10 h/14 h(Ph10),12 h/12 h(Ph12),14 h/10 h(Ph14)and 16 h/8 h(Ph16).The effects of different photoperiodic treatments on the growth indicators and the formation of antioxidant enzymes,photosynthesis,chlorophyll content,chlorophyll fluorescence,C and N contents of the three barnyard grasses at different developmental stages were investigated.We investigated the effects of different photoperiod treatments on the growth and development of three species of barnyardgrass,clarified the barnyardgrass types and their critical photoperiodic day length according to the response of plant flowering to photoperiod.And we revealed the response mechanism of three species of barnyardgrass to photoperiod.Thus,the optimal photoperiod for breeding and cultivation of barnyardgrass can be screened,which provides a theoretical basis for the proper cultivation and planting of high-quality forage grasses in China.The main research results are as follows:(1)Photoperiod had significant effects(P<0.05)on plant height,stem diameter,leaf width,leaf length and leaf number,and highly significant effects(P<0.01)on above-ground biomass,seed yield,flag leaf area and spike characteristics of E.crusgalli(L.)Beauv.var.mitis(Pursh)Peterm.’Nngxia’,E.frumentacea(Roxb.)Link and E.crusgalli(L.)Beauv.’Chaomu 1’.The plant height,leaf length and above-ground biomass of the three barnyard grasses showed an increasing trend with increasing light duration,while stem diameter,leaf width,leaf number,flag leaf area,filling rate and spike characteristics all showed an increasing and then decreasing trend.The overall performance of each index under different photoperiod treatments was as follows:E.frumentacea(Roxb.)Link>E.crusgalli(L.)Beauv.’Chaomu 1’>E.crusgalli(L.)Beauv.var.mitis(Pursh)Peterm.’Ningxia’.(2)Photoperiod had significant effects(P<0.05)on the relative cellular membrane permeability,malondialdehyde content,osmoregulatory substance content,antioxidant enzyme activity,chlorophyll content,photosynthetic parameters and chlorophyll fluorescence parameters of the three barnyard grasses.The relative membrane permeability,malondialdehyde content,intercellular CO2 concentration(Ci),osmoregulatory substance content and antioxidant enzyme activity of the three barnyard grasses tended to decrease and then increase,while chlorophyll content,net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)tended to increase and then decrease at each reproductive stage with the increase of light duration,and chlorophyll content tended to decrease with the advance of reproductive stage.In addition,the C and N contents in the leaves of the three barnyard grasses showed a trend of increasing and then decreasing as the fertility period progressed;and the C and N contents as a whole showed significantly higher under the long daylight treatment than the short daylight treatment.(3)All three barnyard grasses were short-day plants,and flowering was significantly delayed under the long-day(16 h)treatment,and the barnyard grasses did not spike and flower.The critical photoperiodic day length was 13.7778 h for E.crusgalli(L.)Beauv.var.mitis(Pursh)Peterm.’Ningxia’;13.5926 h for E.frumentacea(Roxb.)Link;and≤14 h for E.crusgalli(L.)Beauv.’Chaomu 1’.(4)Among the growth and physiological indicators of the three forage grasses,aboveground biomass showed significant positive correlations with flag leaf area,spike weight,chlorophyll content,net photosynthetic rate,PSII maximum photochemical efficiency and PSII potential activity,and significant negative correlations with cell membrane permeability,malondialdehyde and proline content.In summary,E.crusgalli(L.)Beauv.var.mitis(Pursh)Peterm.’Ningxia’,E.frumentacea(Roxb.)Link and E.crusgalli(L.)Beauv.’Chaomu 1’ are short-day plants,the growth and physiological characteristics of three barnyard grasses are regulated by photoperiod.The medium light duration(12 h)can significantly promote the synthesis of chlorophyll in the leaves of three species of barnyard grasses,which is conducive to the accumulation of photosynthetic pigments,thus enhancing the efficiency of light energy transfer and utilization by the leaves,enhancing photosynthesis,synthesizing and accumulating more photosynthetic products,thus increasing the yield of forage grasses to a greater extent in a shorter period of time through suitable light duration,which can provide a theoretical basis for the proper cultivation of high-quality forage grasses,contributing to the sustainable development of livestock industry in China.