Effect Of Different Combinations Of Nitrogen, Phosphorous And Potassium On The Growth And Development Of Dahlia Pinnata S

Taking Dahlia pinnata ‘Shenmeihong’as experiment material, the effects of N, P and Kformulated fertilization on morphological, physiological and biochemical parameters of dalialeaves, nutrients contents in leaves and contents of soil available nutrients through potexperiment with “3414” incomplete regression-orthogonal design were studied. Through theresponse mechanism of the above indexes under different N, P and K, the paper explored thelodging-resistant mechanism and screened appropriate lodging-resistant index. The resultsprovided the basic data for the future cultivation. It also provided the scientific theoreticalfoundation for applying fertilizer rationally in dahlia. The main results of this paper were asfollows:1. N, P, K affected dahlia’s growth. In a certain range, stem diameter, leaf area, functionleaves, total flower numbers, petals, flower diameter, florescence and tuber weight increasedwith the quantity of fertilizer increased. But excessive fertilization inhibited the growth ofDahlias. It is concluded that moderate fertilizering promoted its growth and development,delayed its aging and improved ornamental value of dahlia ‘Shenmeihong’, but excessivefertilizer brought inhibition.2. N, P, K affected dahlia’s nitrogen metabolism. When the ratio of N and K isreasonable, chlorophyll content and photosynthetic rate were higher, the period of high lighteffect is long. It is profitable for accumulating the assimilation product and improving theactivities of nitrate reductase (NR). Then it affected the nitrogen metabolism directly,promoted nitrogen absorption and increased the total nitrogen contents. Nitrogen contentreflected the physiological activity in a way.3. N, P, K affected physiological characteristics of dahlia. If usage of N, P and K wasreasonable, dahlia’s superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) alsoimproved significantly. It is concluded that moderate fertilizering promoted the activity of theprotective enzyme, improved cell to scaveng capability to active oxygen free radicals,effectively controled membrane lipid peroxidation levels, maintained the stability of plasmamembrane to greatest extent and delayed its aging process. Malondialdehyde (MDA) contentdecreased significantly, the stability of plasma membrane was enhanced, the penetration ofmembrane was restrained, and the protective function of cell membrane was strengthened. If using excessive or too little fertilizer, the plant suffered salt stress in a level. Production andremove of free radical was out of balance, and then the membrane lipid peroxidationhappened by the metabolic disorder and plasma membrane was damaged, which led to theleak out of massive ions and the accumulation of MDA. If usage of N, P and K is notreasonable, stress resistance of dahlia was weakened and was vulnerable to stress of adversityin growing process. Superoxide dismutase activity, catalase activity and peroxidase activity ofdahlia’s leaves decreased, proline content increased shaply.4. The effects of different fertilizing treatments on N, P, K contents of plant weredifferent. NPK single factor analysis indicated that N, P and K fertilization improvedsignificantly N, P and K contents; no obvious interactions were found between nitrogen andphosphorus, nitrogen and potassium, phosphorus and potassium, respectively, however, thevalue of N, P and K contents were greatly influenced by phosphorus dosage. Compared withthe control, contents of soil available nutrients in different fertilizing treatments all increased.Significant correlations existed between N, P and K applications and soil available nutrientcontents, positive correlation between nitrogen application and soil available nitrogen,positive correlation between phosphorus application and soil available phosphorus, positivecorrelation between potassium application and soil available potassium. It is concluded thatfertilizer can greatly increase the contents of total N, P, K in leaves. With the increasing of theapplication rates, nutrients contents in leaves increased gradually. The amount of availablenutrient in soil can be greatly improved with application of N, P and K in flowering period.As the application rates inereased to the level of N3, P3and K3, contents of soil availablenitrogen, available phosphorus and available potassium respectively reached at most.Under this experimental conditions and synthesizing each index, the effects of N2P2K2was the most significant to dahlia.