Estimation of physiologically active zinc in maize by biochemical assay

Abstract

The enzymes ribonuclease, aldolase and carbonic anhydrase were evaluated as biochemical assays for physiologically active zinc in maize. Seedlings were cultured for 14 or 30 days on a black-earth soil with factorial combinations of phosphorus and zinc fertilizers so as to produce in the leaves varying levels of active zinc at a constant level of total zinc. Enzyme activity was correlated with plant growth, leaf nutrient composition and the occurrence of visual symptoms of zinc deficiency.Ribonuclease and aldolase activities in leaf tissues were insensitive to the changes in active zinc concentration, though aldolase activity was sensitive to phosphorus deficiency. In contrast, leaf carbonic anhydrase activity correlated well with the onset and correction of zinc deficiency symptoms and, as early as 14 days after emergence, was more sensitive to the deficiency than was plant growth.The sensitivity of carbonic anhydrase to changes in active zinc and its specificity for such changes were further examined in 10 to 30 day-old plants grown in solution culture. Zinc was added to plants which had been cultured without zinc for 16 days. A 2.5-fold increase in carbonic anhydrase activity preceded responses by either zinc concentration or plant growth.We propose the use of leaf carbonic anhydrase as an index of active zinc in maize, particularly to supplement inorganic analysis in the diagnosis of zinc deficiency when much of the zinc in the plants is inactive. The assay is simple, is sensitive to and specific for zinc status, and enables early detection of a deficiency before irreversible biochemical events predispose a large yield reduction. 395Plant and Soil 63, 395-406 (1981).

Effect of magnesium or zinc supplementation at the background of nitrogen rate on nitrogen management by maize canopy cultivated in monoculture

“…These relationships indirectly stress the significance of both nutrients in controlling leaf photosynthetic activity and explain the importance of this plant part as a starch donor for developing grains (Rajcan and Tollenaar 1999). While the data obtained in treatments NPK + Mg can be related to the presence of Mg in the chlorophyll molecule, in those outlined from NPK + Zn, the effect of zinc on the extended length of the period of carbohydrates synthesis by leaves was reported by Gibson and Leece (1981) and Guliev et al (1992). Total nitrogen content (TNC) in maize plant parts at its physiological maturity showed the year-to-year variability, with the lowest coefficient of variation (CV) attributed to kernels and cob cores.…”

Cumulative and Residual Effects of Zinc Sulfate on Grain Yield, Zinc, Iron, and Copper Concentration in Corn and Wheat

“…Corn is a sensitive plant to Zn deficiency. Zinc deficiency resulted in a decline in the activity of carbonic anhydrase, aldolase and ribonuclease and a declined Zn concentration and a dry matter decrease in aerial parts (shoots) in corn (Gibson and Leece, 1981). In Iran, there are greater than 400,000 hectares cultivated for corn production.…”

Improving key enzyme activities and quality of rice under various methods of zinc application

“…As combined soil+foliar application of Zn increased the concentration of physiologically active Zn in the leaves, it enhanced the CA activity in leaves. It was earlier reported that activity of CA decreased in many plant species as a consequence of Zn deficiency (Gibson and Leece 1981). A Zn inefficient wheat genotype when grown under Zn deficient conditions showed reduced activity of CA (Hacisalihoglu et al 2003).…”