Impact of Essential Micronutrient, Zn, on Growth and Chlorophyll Biosynthesis in Young <i>Zea mays</i> Seedlings

Abstract

The present study analyses growth and chlorophyll biosynthesis in young maize seedlings in response to Zn supply over a wide range of concentrations. Supply of 0 - 5 mM ZnCl 2 to 3 days old light grown maize seedlings led to gradually increased accumulation of Zn in the shoot tissue, while in the root tissue substantial increase was observed at/and above 0.1 mM ZnCl 2 . Zn supply significantly reduced the overall growth of maize seedlings mostly at 1 - 5 mM ZnCl 2 exerting strong correlation and the observed effect was more substantial for root tissue. Amongst the biochemical parameters, increase in protein and proline content was more prominent in root tissue than the shoot, while RNA content was reduced in shoot tissue. Zn treatment to light grown seedlings significantly increased the chlorophyll, carotenoid content, while in dark grown seedlings it had marginal/no effect. Delta amino levulinic acid (ALA) content in both the regimes was increased at higher Zn concentrations. Also ALA synthesis was increased in both the regimes, but non significantly. Zn enhanced ALA dehydratase (ALAD) activity of light as well as dark grown seedlings being significant in former. The results demonstrate that the Zn accumulation and growth effect at higher Zn concentrations in maize depend upon the tissue with root as the target site and shoot growth are mainly influenced by ALA and subsequently ALAD in maize seedlings.