Growth And Physiology Of Maize Seedling Response Under Water Stress

The pot experiment with Liyu18researched on the effect of maize seedling morphology,root structure, biomass, root activity, protective enzyme system and photosyntheticfluorescence explore under different levels of water treatments in summer and spring sowing.In order to explore growth and physiology responses under water stress at maize seedlingstage, to provide a theoretical basis for revealing the drought resistance of maize seedlingsmechanism for of maize drought resources election and dryland cultivation research toprovide a reference. The main results were listed as follows:1. Mild water stress (LS) has little effect on plant height, moderate (MS) and severewater stress (SS) was significantly lower (P <0.05). Root length and plant height of springsowing are more consistent performance than the summer sowing. Water stress reducedmaize seedling stage of shoot and root biomass, the effect of aboveground part is greater thanthe roots. With the intensification of the degree of water stress, root shoot ratio increases; itshowed a downward trend with the duration of stress time in summer sowing and springsowing. With the duration of stress time, the former showed a downward trend, the aftererfirst increased and then decreased.2. Effect of different water stress on maize root morphology had differences. MS and SSbrought the total root length, root surface area, root volume as well as the different diameterof the root length and root surface area was significantly lower than CK (P <0.05), while theLS has little effect. All the water stress treatments in summer sowing could increase the ratioof fine roots (0.05~0.25mm) and reduce that of coarse roots (0.5~1mm), while springsowing showed the opposite trend.3. Root activity increased with stress intensified, showed a decreasing trend after thefirst increase with the duration of stress time. The chlorophyll a, chlorophyll b and carotenoidcontent of mild (LS) and moderate (MS) water stress increased compared with the CK in thesame period; With the prolonging of water stress, the chlorophyll a, chlorophyll b andcarotenoid content showed a downward trend. The SS of spring sowing in addition to aminimum of the15th day, the remaining days of chlorophyll a, chlorophyll b and carotenoidcontent were the highest. Chla/b of LS in summer sowing has no significant difference with CK during30days, while MS and SS also show that during former25days, until the30thdayit significantly reduce. With prolonged stress time, the content of chlorophyll a, chlorophyll b,and carotenoids are down, while Chla/b of summer sowing first down then up, while springsowing showed down.4. Summer maize suffered water stress, with increase of the degree of stress, MDAcontent increased more. The degree of oxidative damage about root membrane lipidperoxidation was more than leaf under water stress. The spring sowing trials indicated thatintermittent accumulation of MDA with the stress time prolonged; impact of water stress onthe root MDA content is much smaller than leaf, the leaf is the main place of the maize MDAaccumulation. Root soluble protein content was less than leaves in summer maize, the SStreatment soluble protein content were significantly decreased in roots and leaves, leaves ofMS treatment is no significant after15thday, whiel the root fluctuations; LS has always beenat a high level. The spring sowing tests showed, with the duration of stress time, solubleprotein content showed a trend of decreased and then increased; only25thday after sowingstress treatment significantly different (P <0.05), the rest of the period of stress tratments withCK in the same period differences are not significant.5. The lesf SOD of summer sowing seedling under water stress is not sensitive. RootCAT activity is less than the blade. With the intensification of the stress degree, showing firstincreased and then decreased; each treatment showed downward trend with the stress timeprolonged. Root POD activity was greater than leaf. Water stress increased POD activity inleaf, fluctuated in root; downward trend with the duration of stress time in leaf, and increasedfirst and decreased in root. The spring sowing test showed that, POD synchronization leavesand roots to reduce oxidative damage, SOD and CAT complementarity between the leavesand roots under water stress. In early stress (the15th,20thday), CAT than SOD, POD moresensitive in maize leaves; Maize root in moderate water stress mainly dependent CATreduced oxidative damage roots, while under severe water stress mainly relies on CAT andthe later CAT and POD together to reduce oxidative damage.6.The summer sowing tests showed that SS significantly reduces the photosynthetic rate,transpiration rate, stomatal conductance and instantaneous water use efficiency, increasedintercellular CO2concentration and stomatal limitation value (P<0.05); MS significantlyreduced transpiration rate and stomatal conductancedegree (P <0.05), LS significantlyincreased transpiration rate (P <0.05). LS, MS damaged PSⅡ, reduced photosyntheticelectron conversion ability, but to increase self-protection, through heat dissipation to avoidthe thylakoids was excessive. SS stress caused a large degree damage to photosyntheticstructure. The spring sowing results showed that water stress impacted transpiration greater than photosynthesis; Maize mainly reduce the transpiration rate to increase water useefficiency under water stress. PS II reaction center under water stress to antenna pigmentsabsorb excess light energy after thermal dissipation capability was still strong; the degree ofdamage to the photosynthetic apparatus was small.