BIOSÍNTESIS DE HIDRATOS DE CARBONO NO ESTRUCTURALES Y SU DISTRIBUCIÓN EN PLANTAS DE FRIJOL EJOTE

Resumen

Sucrose and starch are the main products of photosynthesis in higher plants, sucrose being the main sugar transported from the leaves to the rest of the plant. Sucrose, in addition to providing carbon and energy to developing organs, is important in responses of defense and tolerance against environmental stress. One of the main
factors regulating both sugar metabolism and the source-sink relationship (distribution) is the nutritional state of N. In the present study, we examined the responses of these physiological processes in relation to N conditions ranging from deficiency to toxicity. That is, N was applied to the nutrient solution as NH₄NO₃ at the following
rates: 1.5, 3.0, 6.0, 12.0, 18.0 and 24.0 mM. N deficiency stimulated the sucrose synthesis, yielding the highest values for fructose-1,6- biphosphatase and sucrose phosphate synthase activities. Under these stressful conditions sucrose translocation to the roots increased, thus explaining why root growth was un affected. On the contrary, N toxicity not only stunted general growth, but also stimulated significantly sucrose degradation associated with the highest activities of sucrose
synthase, as well as of the acidic and alkaline invertases. Finally, the sucrose/starch quotient could be considered a good indicator of N sufficiency in green beans.