RESPONSE OF TWO NEWLY DEVELOPED CORN GENOTYPE (Zea mays, L) TO SOME TRACE ELEMENTS UNDER SALT STRESS THROUGHOUT THEIR GROWTH LIFE SPANE: 1- MORPHOLOGICAL AND GROWTH CHARACTERS

Two pot experiments were carried out at the greenhouse and laboratories of the Agricultural Botany Department, Faculty of Agriculture, Mansoura University, Egypt during the two seasons of 2002 and 2003 to study to what extent the experimented treatments of some trace-elements applied either as a spray or as a soil feeding may improve salt tolerance and reduce of salt induced necrosis in maize plants; Zea mays, L. Two newly cultivars were chosen; Bachaier 13 single cross and TWC 310 denoted cultivar (1) and cultivar (2), respectively. Four levels of artificial saline sea water having E.C. values of 0.36, 2.5, 5 and 7.5 dsm-1 were used and denoted control, low, high and highest level respectively. Zn, Fe and /or Mn trace-elements were investigated. The experiments were laid out as a factorial complete randomized block design system with 8 replication, four of them were used for the morphological as well as growth characters and analyzed statistically. The general observation was the higher values of growth parameters in cultivar (1) than those obtained with cultivar (2) throughout the experimental period during the two growing seasons. The plants in the two cultivars were growing slowly under salinity and were dwarfing, stunting, inferior in size and unhealthy in general appearance. The effect of salinity was more pronounced in cultivar (2) than cultivar (1). Plants were shorter, thin and the rate of leaf production and leaf size were much reduced. Plants showed obvious changes in colour if compared to the control plants. As the salinity level increased the stunting was more noticeable; the leaves of the two cultivars become dull coloured, often bluish-green, and frequently coated with a waxy deposit. Plants of cultivar (2) failed to grow up to the 2nd sample; tassiling stage, under salinity even at 2.5 dsm-1. With respect to the power of survival which is taken as a criterion of salt tolerance, it was found that cultivar (2) plants could not tolerate any level of salinity even at 2.5 dsm-1, while cultivar (1) plants tolerate salinity up to 5 dsm-1 and died only at the level of 7.5 dsm-1. Salinized plants started to bloom earlier than did in the control in cultivar (1). Such effect was increased with an increase in salinity level and amounting to 5-7 days at the 7.5 dsm-1. The effects of trace-elements indicated that Zn, Fe and/or Mn, especially Zn treatments, improved growth of the two cultivars during the two growing seasons. The proven efficiency of these elements was more pronounced in cultivar (1) plants than did in cultivar (2) and depending on the salinity levels. The interactions treatments indicated that, micronutrients treatments counteracted the harmful effect of salinity on cultivar (1) plants compared with the corresponding control. Therefore, the treated plants tolerate salinity up to the highest level of salinity; 7.5 dsm-1. In cultivar (2) plants, Zn treatments only improved their tolerance but up to the high level; 5 dsm-1 only whereas other nutrients failed to improve the plants to grow under the salt stresses used, since the salinized plants died before tasseling stage.