Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Absorción y asimilación de nitrato y amonio en Opuntia ficus-indica (L.) Mill. en condiciones de hidroponia

Auteur : Gallegos Vázquez, Clemente

Université de soutenance : UNIVERSIDAD AUTONOMA DE NUEVO LEON

Grade : DOCTOR EN CIENCIAS AGRICOLAS 1998

Description
Purposes and Methods of Study : The nitrogen (N) is the element of higher influence in the growth of cactus pear (Opuntia spp). The objectives of this research work were ; a) to understand the ion kinetics absorption of NO3’ and NHj+ , b) study the cffcct of several relationships among N-NO3 and N-NH4 in the activity of the enzymes nitrate reductase (NR) and Glutamate synthase (OS), and c) evaluate the effect of the nitrate and ammonium nutrition on the level and accumulation of nutriments and their relationship with some physiologic processes of plants of Opuntia ficus-indica (L.) Mill. For such effect, two consecutive experiments were developed in hydroponics conditions. In the Experiment I, Ca (NOj^tk O was used and (NH4)2S0 I like N sources to get a concentration of 150 mg L"’ of N. An experimental design of random blocks was used, with seven replications. The ion speed absorption was evaluated by the depletion method. In the Experiment 2, five N-NO^N-NFL relationships were studied, 1:0 (150 mg I/1 ofN-N0 3 : 0 mg I/1 of N-NH4), 2:1 (100:50), 1:1 (75:75), 1:2 (50:100) and 0:1 (0:150)]. An experimental design of random complete blocks was used, with four replications with a factorial arrangement of treatments, Several organs of the plant, root, the activity of the enzymes, nitrate reductase (ANR), glutamate synthase (AGS), NO3 and protein content were "in vivo" evaluated, at 21 days after establishment of the experiment. It was measured the pH and the tritable acidity m growing buds of cladodes, each 4 h during 24 h of the day. In the final stage of the research work, it was carried out a destructive sampling, in order to determine the content of N, P, K, Ca and Mg of mother cladodes and roots
Contributions aud Conclusions  : In the results can be observed a high absorption of nitrogen, when N-NO3 was used as a nitrogen source in the nutritious solution ; this bigger absorption of N-NOj can be associated with a higher production of dry matter from buds and a increment in the pH of the nutritious solution compared with the N-NH4. It was registered a high activity of the enzymes nitrate reductase and glutamate synthase when the nutritious solution was subministered with a higher relationships of N-N03:N-NH4, confirming the dependence of the RNA from the concentration of N-NOj in the nutritious solution. Both enzymes had a similar behavior, registering their higher activity in the root. The average nitrates content in the vegetable tissue was higher according to the supply of N-NO) from the relationships N-NOjiN-NFU in the nutritious solutions, corroborating this dependence of the concentration of N-NO3 in the external media. The highest content of soluble proteins, it is associated to bigger concentrations of N-NH4 in the nutritional solution, locating the concentrations of this nitrogen form in the root. The concentration of N, P, K, Ca, and Mg of the of prickly pear plant was not influenced for the supply of several relationships of N-NO3 and N-NH4, detecting high significant differences in function of the age and type of organ of the plant. The microclimatic and plant variables showed sharp fluctuations during days. The night accumulation of acid, expressed in % of malic acid, it constitutes an appropriate indicator of the levels of absorption of CO2 in the cactus pear plant.

Mots clés : Arid Land Agriculture, Plant Nutrition and Cactus Pear Ecofisiology and Productivity

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