Water Consumption And Responoses To Regulated Deficit Irrigation Of Capsicum Annuum In Arid Desert Area

The effect of regulated deficit irrigation(RDI) on water consumption, water consumptionmodulus, water consumption intensity, plant growth, fruit production, physiological andbiochemical characteristics in the leaves were researched taking the fresh Capsicum (Longjiao2)and drying Capsicum(Meiguohong) as materials, designing four irrigation level including fullirrigation(CK), light RDI, medium RDI and severe RDI at planting-fruit setting stage, middlefruiting and late fruiting stage, respectively aiming at researching water consumption of Capsicumin arid desert area, discussing mechanism of drought resistence, water saving and yield increasingunder RDI and providing some theoretical basis for rational irrigation and high efficient plantingof Capsicum in arid area. The results are as follows:1. Water consumption was significantly positively correlated to irrigation amount ofCapsicum cultivated in open field (P<0.05, r=0.955). Compared with full irrigation,waterconsumption of Long jiao2(LJ) was reduced by7.49%,11.00%and14.21%,15.83%under mediumand severe RDI at planting-fruit setting and middle fruiting stage, water consumption ofMeiguohong(MGH) was reduced more with reduction of9.55%,11.80%and18.33%,20.08%.Total water consuption of MGH(470.08mm) was significantly lower than of LJ (514.14mm)under full irrigation. The water consumption modulus of the two varieties showed in the order ofmiddle fruiting stage(46%), planting-fruit setting stage(40%), late fruiting stage(14%), waterconsumption intensity of the two varieties also appeared in the same order and water consumptionintensity at each growth stage of MGH(4.81mm/d,4.18mm/d,2.79mm/d) was markedly lower thanof LJ (5.32mm/d,4.31mm/d,3.46mm/d). RDI significantly decreased water consumption modulusand intensity of the stage ued RDI and water consumption intensity of MGH was significantlylower than that of LJ under medium RDI at planting-fruit setting stage and RDI at middle and latefruiting stage. The crop coefficient(K c) at middle fruiting stage was the maximum for Capsicumcultivated in in arid desert region, and of LJ and MGH changed in the order of middle fruitingstage(1.16and1.05), planting-fruit setting stage(0.88and0.85), late fruiting stage(0.85and0.69)under full irrigation. RDI significantly reduced and difference in of the two varieties wassignificant under RDI at middle and late fruiting stage.2. Medium and severe RDI at planting-fruit setting and middle fruiting stage significantlydecreased plant height, plant diameter and leaf area index (LAI) of Capsicum, and plant growth ofLJ was more sensitive to water deficit than MGH. Under severe RDI at planting-fruit setting andmedium and severe RDI at middle fruiting stage, fruit number per plant, fruit weight, per plant yield and total yield of LJ reduced significantly and fruit number per plant, per plant yield and totalof MGH also decreased distinctly. Capsicum yield was maximaly decreased by water deficit atmiddle fruiting stage being water critical period.3. Under medium RDI at planting-fruit setting stage, water use efficiency of LJ and MGHbased on water consumption(13.29kg. m-3and7.44kg. m-3) and on irrigation amount (18.76kg.m-3and10.08kg. m-3) reached the maximum. Dry matter accumulation per plant returned to thecontrol level and ratio of dry matter distributed in stems, leaves and roots was proper, whichimproved the fruit production and significantly increased the content of Vc and total soluble solid.Taking above data into consideration, soil water content should be controlled between55%and65%of field water capacity at planting-fruit setting stage and75%to85%at middle and latefruiting stage, which can realize high yield, good quality and water saving cultivation of Capsicumin arid desert area.4. RDI reduced photosynthetic pigment content, net photosynthetic rate(Pn), transpirationrate(Tr), gas conductance(Gs) and PSâ…¡activity in the leaves of Capsicum. There was no obviouschanges in the content of Chla+b, Car and PSâ…¡activity under light RDI, but Pn and Tr decreasedsignificantly with more decline in Tr, when Pn reduced, Gs and interlellular CO2concentration(Ci)also cut down but stomatal limitation(Ls) increased, which indicated that the reduction of Pn wasmainly caused by stomatal limitation. Medium RDI at planting-fruit setting stage caused moresignificant reduction in Tr than in Pn reaching maximal WUE at leaf level, maximal photochemicalquantum efficiency of PSâ…¡(Fv/Fm) and actual photochemical quantum yield of PSâ…¡ (PSâ…¡)appeared no significant reduction and heat dissipation increased, which showed stomatal limitationwas still the main factor causing Pn reduction. Under severe RDI at planting-fruit setting stage andmedium and severe RDI at middle fruiting stage, the content of photosynthetic pigments, Pn, Trand WUE decreased significantly, Fv/Fm and PSâ…¡of PSâ…¡were markedly inhibited, thermaldissipation decreased, non-stomatal limitation was responsible for reduction in Pn. The changerange of photosynthetic parameters were smaller in MGH than in LJ and MGH maintained higherWUE at leaf level and photochemical PSâ…¡activity under the same RDI level, which indicates thatMGH better adapts to dry desert-oasis environment.5. RDI caused significant decrease of relative water content(RWC) and increase of watersaturation deficit(WSD) and ratio of bound water to free water(Va/Vs) enchancing droughtresistence of Capsicum. Under light and medium RDI at planting-fruit setting stage, proline(Pro)and soluble sugar(SS) might be the main osmotic regulation substances for LJ drought resistence,Pro mainly carried out osmotic adjustment in MGH and played improtant osmotic regulation rolein the two varieties under severe RDI. Under medium and severe RDI at middle fruiting stage, Pro and SS played main osmotic regulation function and SP accumulated significantly under severeRDI taking an important role in osmotic adjustment. Medium RDI at planting-fruit setting stageresulted in some membrane peroxidation in the leaves of Capsicum, but superoxidedismutase(SOD) and catalase(CAT) were induced to reduce peroxidation extent. Lipidperoxidation was intensified significantly under severe RDI and anti-oxidative capability decreasedmarkedly and it was SOD, CAT and asorbic acid(AsA) that reduced lipid peroxidation in MGH.Under medium and severe RDI at middle fruiting stage, the ability of antioxidant system toscanvege active oxygen markedly decreased, which resulted in significant membrane impairment.The membrane impairmment of LJ was sigificantly more than MGH by severe RDI atplanting-fruit setting stage and medium RDI at middle fruiting stage.6. Rewater at middle fruiting stage after light and medium RDI at planting-fruit setting stageproduced compensatory effect in the plant diameter, LAI, photosynthetic pigment content ofCapsicum, osmotic regulation and antixodant system produced some biochemical compensatoryrole and memberance system was healed but rewater after severe RDI could not producecompensatory effect for Capsicum.The above results show that under medium RDI at planting-fruit setting stage Capsicumcultivated in arid desert area accumulated Pro and SS in the leaves to improve osmotic potentialensuring growth and photosynthetic processes, protected membrane structure and maintainedphotochemical activity of PSâ…¡by mechanisms of scavenging reactive oxygen of SOD and CATand thermal dissipation, improved WUE at leaf level by stomatal regulation, distribution ofphotosynthates promoted fruit production and rewater produced compensatory effect in plantdiameter, leaf area, photosynthetic pigment content, which is helpful to attain the goal of watersaving, high efficiency and good fruit quality preventing from significant yield reduction. MGHshows better adaptability to drought and potential of water saving and yield increasing.The research determined reasonable RDI period and degree of Capsicum cultivated in ariddesert area, and revealed the mechanisms of drought resistance, water saving and yield increasing,which has practical significance in making scientific irrigation schedule and exploiting productivepotential of Capsicum.