Comparative Study On Physiological Mechanism Of Response Of Stay Green Sorghum And Maize To Drought Stress

Researches into stay green sorghum and maize were conducted under pot cultivation inthe experimental base of Shenyang Agricultural University from2010to2011. The aim ofthe study was to seek out difference between stay green sorghum and maize in physiologicalmechanism under drought stress and to provide academic basis of promoting the applicationof stay green and guiding to the improvement of crop resistance. The main results were asfollows:1. Compared with the non-stay green sorghum and maize, stay green sorghum and maizeshowed higher root dry weight, root/shoot, total root length, root surface area and rootreducing capacity. Under water stress, root morphology indexes and reducing capacity ofstay green sorghum and maize decreased in smaller extents than did non-stay green sorghumand maize. Compared with stay green maize, stay green sorghum had higher root/shoot, androot reducing capacity decreased in smaller extents than those of did stay green maize underdrought stress.2. Under normal water condition, Chla, Chlb and total Chl content of stay green sorghumand maize were higher than those of non-stay green sorghum and maize. From floweringstage to filling stage, the content of Chla, Chlb and total Chl in stay green sorghum andmaize decreased less than those in non-stay sorghum and maize. Under drought stress, Chlcontents, Pn, Gs, Tr, φPSⅡ, qL, F0, FV/FMand rETR of stay green sorghum and maize wereless influenced than those of non-stay green sorghum and maize by water stress. Indexes ofphotosynthetic and fluorescence of stay green sorghum and maize decreased in smallerextents than those of did non-stay green sorghum and maize. The NPQ of non-stay greensorghum and maize was higher than that of stay green sorghum and maize under droughtstress. The PMand α of rapid light curves of stay green sorghum and maize decreased insmaller extents than did those of non-stay green sorghum and maize.There were different changes in Chl content, photosynthetic indexes and chlorophyllfluorescence parameters between stay green sorghum and maize under drought stress. TheChl content of stay green sorghum was larger influenced than that of stay green maize duringthe flowering stage and was smaller influenced than that of stay green maize during thefilling stage by water stress. From flowering stage to filling stage, the Chl content of staygreen sorghum decreased in smaller extents than did that of stay green maize under normalwater condition and drought stress. The Pn, Gs and Tr of stay green maize were sensitive towater stress during flowering stage. The Pn, Gs and Tr of stay green sorghum were sensitiveto water stress during filling stage. The φPSⅡ, qL, rETR, PMand α of stay green maizedecreased in larger extents than did those of stay green sorghum under drought stress. TheNPQ, FV/FMand F0of stay green sorghum were largely influenced than those of stay green maize during the flowering stage and were smaller influenced than those of stay green maizeduring the filling stage by water stress. In addition, from flowering stage to filling stage, thechlorophyll fluorescence parameters of stay green sorghum decreased in smaller extents thandid those of stay green maize under drought stress.3. The SOD, CAT, POD activity and·OH clearance of leaf and root in stay greensorghum and maize were bigger than those of non-stay green sorghum and maize. Theprotective enzyme activity of leaf and root in stay green sorghum and maize had littlesensitive to water stress and decreased in smaller extents than did that of non-stay greensorghum maize under drought stress. The content of MDA and O₂^-of leaf and root in staygreen sorghum and maize were lower than their control and increased smaller extents thandid those of their control under drought stress.There were different changes in protective enzyme activity of leaf between stay greensorghum and maize under drought stress. The SOD, POD activity and·OH clearance of leafin stay green sorghum increased larger extents than did those of stay green maize underdrought stress. From flowering stage to filling stage, the SOD, POD activity and·OHclearance of leaf in stay green sorghum decreased in smaller extents than did those of staygreen maize under normal water condition and drought stress. The regulative ability of leafCAT activity in stay green maize was better than stay green sorghum. The content of MDAand O₂^-of leaf in stay green maize increased larger extents than did those of stay greensorghum under drought stress. The trend of active oxygen metabolism of root in stay greensorghum and maize were the same as leaf under drought stress.The SOD and POD activity of leaf were bigger than root,and CAT activity of root wasbigger than leaf in sorghum and maize. The·OH clearance of leaf was the same as root. Theprotective enzyme activity of coordination of leaf and root in maize was worse than that ofsorghum. The correlation analysis between protective enzyme activity and Chl content ofsorghum and maize showed that CAT and·OH clearance were mainly regulators of maize;SOD and POD were mainly regulators of sorghum.4. Compared with the non-stay green sorghum and maize, stay green sorghum and maizeshowed higher bound water content and relative water content. Under drought stress, the freewater content, relative water content and nitrate reductase of stay green sorghum and maizedecreased in smaller extents than those of did non-stay green sorghum and maize; watersaturation deficit and relative conductivity of stay green sorghum and maize increasedsmaller extents than those of did non-stay green sorghum and maize. Compared with thenon-stay green sorghum and maize, the soluble sugar and soluble protein content of leaf androot in stay green sorghum and maize were higher and the soluble sugar and proteinadjustment ability of leaf and root in stay green sorghum and maize were better under drought stress; the proline content of leaf and root in stay green sorghum and maize wassignificantly increased under drought stress.There were different changes in leaf water, cell permeability and regulating substancebetween stay green sorghum and maize under drought stress. Under water stress, the freewater content, relative water content and water saturation deficit of stay green maizedecreased larger extents than those of did stay green sorghum, and bound water content ofstay green maize increased larger extents than that of did stay green sorghum whichindicated the leaf water of stay green maize was lower than stay sorghum. The relativeconductivity of stay green sorghum increased in smaller extents than that of did stay greenmaize, and nitrate reductase activity deceased in smaller extents than that of did stay greenmaize under water stress.The increasing amplitude of proline of leaf and root in stay green sorghum was higherthan stay green maize; the increasing amplitude of soluble sugar content was smaller thanstay green maize; the decreased degree of soluble protein was smaller than stay green maizeunder drought stress.There was significant positive correlation or a significantly positive correlation betweenrelative water content and photosynthetic system in sorghum and maize. The correlationanalysis among proline, soluble sugar and soluble protein of sorghum and maize showed thatsoluble protein was mainly regulators of sorghum and maize; proline and soluble sugar ofsorghum had influence on F0; proline of maize had influence on Chl content, and solublesugar of maize was little influence on photosynthetic system.5. Compared with the non-stay green sorghum and maize, stay green sorghum and maizeshowed higher cytokinin content and lower abscisic acid content under normal watercondition. Hormonal regulation of stay green sorghum and maize was better under droughtstress. In order to adapt to changes of water, cytokinin content of stay green sorghum andmaize could decrease properly, and abscisic acid content could increase effectively.Compared with the stay green maize, the increasing amplitude of abscisic acid content ofstay green sorghum was higher and the decreased degree of cytokinin content was smallerunder drought stress.The correlation analysis among photosynthetic system, leaf water and regulatingsubstance of sorghum and maize showed that regulation of cytokinin and abscisic acid werethe same in sorghum and maize.6. Under drought stress, the changes of chloroplast ultrastructure in non-stay greensorghum and maize showed that the chloroplasts became irregular shape, the starch granulesin chloroplasts disintegrated, the grana became loosely, fat droplets increased in number, anda little of thylakoids could be picked out. The chloroplast lamellae distinguished hardly and arranged disorderly. The chloroplast ultrastructure and chloroplast lamellae in stay greensorghum and maize had little influence by drought stress.There were different changes in chloroplast ultrastructure and chloroplast lamellaebetween stay green sorghum and maize under drought stress. The chloroplast ultrastructureof stay green sorghum had regular shape, and the organelles in chloroplast ultrastructurearranged densely. The chloroplast ultrastructure of stay green maize had loosely shape, andbecame irregularly. There were air space between one organelle and another in chloroplast ofstay green maize. The chloroplast lamellae structure of stay green sorghum was clear, andthylakoids and starch granules could be distinguished easily. Some cylindrical granaesexisted in stay green sorghum leaf cells. Although the grana and thylakoid could bedistinguished in chloroplast lamellae structure of stay green maize, the shape of granaes andthylakoids were unclear and some organelles tended to disintegrate.7. Compared with the non-stay green sorghum and maize, dry matter weight of leaves,sheath, stem and era（panicle） of stay green sorghum and maize decreased in smaller underdrought stress. The yield of stay green sorghum and maize decreased in smaller extents thanthat of did non-stay green sorghum and maize under drought stress. The drought resistanceindex of stay green sorghum and maize were bigger.Leaf, sheath and era（panicle） dry matters of stay green sorghum decreased in smallerextents than those of did stay green maize under drought stress. The yield of stay greensorghum decreased in smaller extents than that of did stay green maize under drought stress.Compared with stay green maize, the drought resistance index of stay green sorghum wasbigger.