Effect Of Water And Fertilizer Regulation On Growth And Physiological Characteristics Of Euaclypt Seedlings

In south of China, commercial seedling production technology of Eucalypt was promotedand used in large area, and achieved good effect. In south provinces of China, with theuneasing expansion of Eucalypt plantation, Eucalypt seedlings demand was rising constantly,so this raised pressing requirements on the current factory nursery cultivation. At presentfactory nursery cultivation of eucalyptus in China mainly used light matrix, but lacked of theresearch on the management of water and fertilizer for container seedling; at the same time,this study researched the management of water and fertilizer on Eucalypt seedling plantation tosolve the issue of disconnection between seedling cultivation and plantation work.The article was based on Eucalypt seedling as test material, at first researched the changeof growth and physiological characteristics performance of2-month old Eucalyptus urophylla×E．grandis seedlings, and then studied the growth and physiological characteristics changesof Eucalyptus urophylla×E.grandis seedlings in different proportion of nutrient solution, at lastfound out suitable soil water content and proportion of nutrient solution for Eucalyptusurophylla×E.grandis seedlings growth; secondly studied the change of Eucalyptus urophylla×E．grandis seedlings photosynthetic physiological parameters and chlorophyll fluorescenceparameters; finally researched the coupling effects of water and fertilizer N、P on the biomassand physiological character of the Eucalyptus urophylla×E.grandis seedlings and establishedthe coupling regressing model of the biomass, finally getting results as following:（1）Form growth and biomass Eucalyptus urophylla×E．grandis seedlings were present todecrease with the decline of soil water content. Every growth index in treatment of80%~90%FC、70%~80%FC were obviously higher than those of60%~70%FC、50%~60%FC,However, there were no significant difference between the80%~90%FC and70%~80%FC,meanwhile root shoot ratio of each treatment was on the rise. The net photosynthetic(Pn)、Transpiration rate(Tr)、Stomatal conductance(Gs)、Fv/Fm and ФPS Ⅱwere trend to decreaseafter increasing, however, Intercellular CO2concentration(Ci) was trend to rise after decrease. Free proline content、MDA、POD activity in the treatment of70%~80%FC decreasedsignificantly, but increased under60%~70%FC and50%~60%FC, root activity decreasedsignificantly, but chlorophyll content increased and there were no significant differencebetween the treatment of80%~90%FC and70%~80%FC、70%~80%FC and60%~70%FC.The correlation analysis showed that there were some correlations among each single index.Principal components analysis showed that the growth and physiological indexes’s qualityevaluation of Eucalyptus urophylla×E．grandis seedlings under different soil water content:70%~80%FC>80%~90%FC>60%~70%FC>50%~60%FC.（2）The different proportion of nutrient solution significantly influenced the growth andphysiological characteristics of Eucalyptus urophylla×E.grandis seedlings, height, diameterand total bilmass in high-nitrogen of Eucalyptus urophylla×E.grandis seedlings weresignificantly higher than those of middle-nitrogen and low nitrogen, height and diametergrowth in low-phosphorous was promoted significantly; The net photosynthetic rate (Pn) ofEucalyptus urophylla×E.grandis seedlings increased with the increasing level of nitrogen,while increased first and then decreased with the increasing level of phosphorous andpotassium. As the change of time(April-June), the chlorophyll and soluble sugar content’schange trend in the leaf was opposite, high nitrogen、phosphorous and potassium couldsignificantly increase the content of chlorophyll, middle-nitrogen could significantly increasethe soluble sugar content of the leaf. The analyses of the growth and physiologicalcharacteristics of Eucalyptus urophylla×E.grandis seedlings indicated that Eucalyptusurophylla×E.grandis seedlings had good performance on the growth and physiologicalcharacteristics in the treatment of high–nitrogen、low-phosphorous、middle-potassium.（3）Water moisture content decreased significantly under the drought stress, thechlorophyll content decreased sharply on the22th day, leaf area did not changed significantly;With the increase of drought stress, Eucalyptus urophylla×E．grandis seedlings leaves netphotosynthetic rate (Pn)、transpiration rate (Tr)、stomatal conductance (Gs) declined continuely,water use efficiency (WUE) increased firstly then reduced, the limiting factor of Pn decreasewas from stomatal limitation to non-stomatal limitation in the13to15days; the maximum photochemical efficiency of PSⅡ(Fv/Fm) and PSⅡactual photochemical quantum yield (ΦPSⅡ)declined than before significantly in the15to17days of the stress, photochemical cu destroycoefficient (qP) and the photochemical cu destroy coefficient (qN) increased firstly thenreduced, and all decreased sharply in the17d, the PSⅡ response center was damaged or lostreversible live. The research showed that Eucalyptus urophylla×E．grandis seedlings couldgrow normally with the soil moisture content>19.2and drought stress duration was less than15d.（4）The sequence of water、nitrogen and phosphorus fertilizer influenced the Eucalyptusurophylla×E.grandis seedlings biomass was soil water content>nitrogen>phosphorus; singlefactor border effect showed that the biomass of the Eucalyptus urophylla×E.grandis seedlingsincreased with the increase of water, but deceased with the increase of nitrogen and phosphorus;The coupling of water and nitrogen had a significant positive interactive effect,but nonsignificant between water and phosphorus fertilizer and between nitrogen and phosphorusfertilizer. The optimal combination of the coupling on the water and fertilizer was79.90%fieldcapacity,5.04g nitrogen fertilizer and12.60g phosphorus fertilizer, at present, the biomass ofEucalyptus urophylla×E.grandis seedlings reached maximum at119.81g.