تاثير تغذيه نيكل و منبع نيتروژن بر انباشت نيترات و اوره و برخي از واكنش هاي اكسيد اتيو در كاهو در محيط آبكشت

چكيده انگليسي :

98 Nickel Nutrition and Nitrogen Source Effect on Nitrate and Urea Accumulation and Some Oxidative Reactions in Lettuce in Hydroponic Culture Fatemeh Hosseini f hosseini@ag iut ac ir November 1 2009 Department of Agriculture Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiA H Khoshgoftarmanesh amirhkhosh@cc iut ac irM Afyuni afyuni@cc iut ac irAbstractNickel Ni is the most recently discovered essential element for higher plants It has been found that Nideficiency depresses urease enzyme activity and other enzymes responsible for nitrate reduction and as aresult increases accumulation of urea nitrate and several amino acids in plant tissues Urea is an importantnitrogen fertilizer in today s agriculture and its suitability for field crops has been well evaluated Urea is awidely used fertilizer because of its low costs easy in handling and high nitrogen content However urea incomparison to nitrate is not a desirable N source for hydroponic grown plants Our knowledge of thecomplete biological significance of nickel for plant productivity is still quite limited However with thedemonstration of the essentiality of nickel in different plant species and the increased use of urea as anitrogen source the importance of understanding the chemistry and biology of nickel and its potential impacton agricultural production has never been greater The impact of Ni nutrition on yield quality and nitratecontent of leafy vegetables such as lettuce is still unknown This work therefore was designed to study theimpact of nickel nutrition and nitrogen source on lettuce yield and quality and accumulation of urea andnitrate in lettuce as one of the freshly consumed leafy vegetables In this study nitrogen was supplied with urea or nitrate ammonium at three concentrations 5 10 and 20mM The lettuce plants were exposed to two nickel levels 0 and 0 04 M in the form of NiCl2 The plantswere harvested 6 weeks after transplanting and the fresh weight of shoots and roots were determined Theshoot nitrate and urea concentrations urease enzymatic activity in the leaves shoot N Fe and Zn contentsand the membrane permeability of root cells were also measured The results of this study indicated that Ninutrition significantly promoted the growth of urea fed plants although it had no significantly affect on thegrowth of nitrate fed plants In this study the shoots and roots fresh weight of the urea fed plants increasedwhen nickel was supplemented The shoot NO3 N concentrations in both nitrate fed and urea fed plants weresignificantly affected by the nickel nutrition Nitrate concentration in the shoots of lettuce plants decreasedsignificantly with nickel nutrition particularly of the high nitrogen levels 20 mM Ni supplement increasedthe urease activity in the leaves significantly The shoot concentrations of urea in the urea fed plants withoutnickel supplement were relatively high in the absence of Ni while it decreased significantly with the nickeladdition The leaf concentrations of total N in the urea fed plants increased with the nickel supplement whileNi had no significant effect on the leaf concentrations total N in the nitrate fed plants It is suggested thatapplication of low levels of Ni in the nutrient solution improve the lettuce yield and quality In addition theplant leaves are safer for human consumption since their nitrate and urea contents are significantly reduced Key Words Nickel Urea Urease enzyme Nitrate Membrane permeability Lettuce

حسيني، فاطمه

تاثير تغذيه نيكل و منبع نيتروژن بر انباشت نيترات و اوره و برخي از واكنش هاي اكسيد اتيو در كاهو در محيط آبكشت

آنزيم اوره آز , نفوذ پذيري غشا و كاهو