Screening And Physiological Mechanisms Of Sweet-waxy Maize Varieties With Resistant Low-phosphorus

This paper studied the effects of major morphological and physiological chara-cteristics of18sweet-waxy maize varieties in the seedling stage under tolerance to lowphosphorus condition. Relative crown dry weight, relative accumulation of phosphorus,relative shoot ratio and relative root dry of different varieties of sweet-waxy maize underlow phosphorus and high phosphorus condition were used as indicators and conductingcomprehensive evaluation, and the18sweet-waxy maize varieties were divided intoresistant low-phosphorus variety, sensitive of low-phosphorus variety, through screening,HuanuoNO.1and RuziniuNo.269belongs to resistant low-phosphorus variety,Caixiangnuo and PincainuoNo.2belongs to sensitive of low-phosphorus variety, andChuanyunuo No.1belongs to moderate resistant low-phosphorus variety. In order to studythe physiological mechanisms of tolerance to low phosphorus of different sweet-waxymaize varieties, using field experiment to study the effect of morphological characteristics,photosynthetic characteristics, phosphorus metabolism, yield and its components ofdifferent types of sweet-waxy maize varieties under different phosphorus levels.The resultswere as follows:1. The pot results that under low phosphorus stress condition, plant height, stemdiameter, shoot and root dry weight, phosphorus content and plant accumulation ofphosphorus declined, root to shoot ratio and acid phosphatase(ACP) activity of leafincreased. The degrees of influence between different varieties of sweet waxy maize varygreatly under low phosphorus stress, this showed significant differences of sweet waxymaize varieties of the tolerance to low phosphorus.2. Depending on the relative value of each indicator of the size of the coefficient ofvariation among species, crown dry weight, root dry weight, phosphorus accumulation andshoot ratio which could be used to evaluate and screen ability of resistance to low-phosphorus as important indexes were selected from the8indexes in the seedling stage.Using comprehensive evaluation method to evaluate the ability of tolerance to low-phosphorus, combining comprehensive fuzzy integrated evaluation method, the relativevalue of each index after normalization coefficient of variation(CV) among varieties weretaken as weight. By fuzzy membership function method,18sweet-waxy maize varietieswere divided classification. 3. The field test results showed that under low phosphorus stress condition, morph-ological characteristics:plant height, stem diameter, plant dry weight, ear height weredecreased; photosynthetic characteristics: chlorophyll content was decreased, netphotosynthetic rate was decreased, stomatal conductance was decreased, transpiration ratewas decreased, intercellular CO2concentration increased; physiological and biochemicalcharacteristics: nitrogen,phosphorus, potassium content and accumulation of their werereduced, root activity, soluble protein content decreased, but POD activity, soluble sugarcontent, ACP activity, free proline content increased. The more deeper level of lowphosphorus stress, the more obvious differences between the indicators, and there weresignificant differences between the varieties of sweet glutinous corn. Compared withsensitive of low phosphorus variety, each index of the phosphorus-resistant variety weresmaller decline and POD, ACP activity, free proline content increased range are larger, Asa result, this might be important physiological mechanism to strong ability resistance tolow phosphorus stress.4. The biological yield and amounts of phosphorus of different sweet-waxy maizevarieties were positively correlated. Under low phosphorus stress, the yield, single bractweight, grain number per row, ear length,1000-grain weight, rows per ear, the width of cob weredecreased significantly, while the resistant low-phosphorus varieties decreased were higherthan extent of the low-phosphorus sensitive varieties decreased. On the yield and itscomponents of indexes correlation analysis showed that yield and single bract weight, grainnumber per row, ear length,1000-grain weight, rows per ear, the width of cob was significantpositive correlation.