EFFECTS OF SALINE STRESS ON GROWTH AND CROP YIELD OF DIFFERENT MAIZE ( ZEA MAYS ) GENOTYPES

Effects of saline stress (NaCl) on yield and vegetative characteristics of eight maize cultivars were studied. The cultivars K3615/1, S.C704, B73, S.C302, Waxy, K3546/6, K3653/2, and Zaqatala were cultivated in two plots of the Astara region: one was with normal soil and the other – with salty one. Salinization reduced the plant height, ear length, ear diameter, number of plant leaves, stem diameter, number of rows in an ear, number of grains in a row, and dry plant mass in all cultivars. Maximal ear length was observed in Zaqatala, B73, and S.C704, and the least one was detected in K3653/2. Salinization decreased crop yield of all the cultivars. Certain correlations between studied parameters were found.


Introduction
Saltiness is one of the restrictive environmental factors for producing agricultural crops that highly causes decrease in agricultural products.From among the whole lands of the world about 100 million hectares (5 %) have high salinity of soil that influences the plant producing and growth [5; 6].Producing the agricultural crops in dry and semi-dry regions of the world is quite low.This is due to the accumulation of salt in the soil [1; 11].Saltiness causes the adverse effects on plant growth that can be provoked by the high osmotic pressure of soil solution (osmotic stress), and especially ionic effects (salt stress), nutritional imbalance or combination of these two factors [2; 10].All the above mentioned factors cause particular negative effect on plant growth and development of biochemical and physiological processes [1; 12].

Materials and Methods
The effects of salinization on growth and yield characteristics of maize were studied in Iran and Azerbaijan in 2007-2008.Seeds of 8 maize cultivars including K3615/1, S.CDS704, B73, S.C302, Waxy, K3546/6, K3653/2, and Zaqatala were cultivated on two plots in Astara: one plot had normal soil but the other one -salty soil.The experiment was carried out as a randomized complete block design made by three replications.During the experiment, characteristics of the plant growth, such as plant height, leaf numbers, leaf relative water content (LRWC), stem diameter and dry mass of the single plant as well as yield characteristics such as the ear length, ear diameter, number of rows in the ear, weight of 100 grains and crop yield per hectare, were measured.
Leaf relative water content (LRWC) was calculated on the basis of Yamasaki & Dillenburg method [15].Two leaves were randomly chosen from middle part of a plant for each replication.At first, leaves were separated from the stems and their fresh mass (FM) were calculated.In order to measure the turgid mass (TM), they were placed in the distilled water into closed containers for 24 hours under 22°C.Being reached the biggest turgid mass the leaves were weighed.Then leaves were placed inside the electrical oven for 48 hours under the 80°C and the dry mass of the leaves (DM) were calculated.All the weightings were done with the scales of 0.001 g accuracy.The LRWC was calculated according to the following formula: In order to measure the plants' dry mass, they were cut as a whole.The grains, ear shanks, stems and leaves were dried at the oven at 60°C for 72 hours and then their dry mass was recorded.Statistical analysis was done on the basis of randomized complete block design.The Duncan's new multiple range test at the 0.05 significance level was used for statistical analysis.

Results and discussion
Data obtained from the experiment showed significant differences between cultivars regarding the most of studied characteristics.As compared to normal conditions, salinization had caused reduction in characteristics' values.The greatest LRWC was found in cultivar B73 under normal conditions and its least amount was found in S.C302 under the saltiness influence.Levent Tuna et al showed that the salinization stress entails a reduction in the LRWC capacity, plant height, stem diameter, number and weight of ear in maize [9].There were significant differences among the cultivars in the plants' heights under the normal and salty conditions.For all the cultivars the salinization caused a decrease in the plants' height.The greatest height was for S.C704 and Zaqatala under normal conditions.In case of both normal and salty conditions, the least amount of the plants' height was seen in K3545/6 (table 1).
Due to the salinization, leaves numbers in all the cultivars were decreased.Under normal and salty conditions, Waxy had the least leaves numbers among the cultivars and there weren't any significant differences among other cultivars under normal conditions.Salty conditions caused decrease in stem diameter in all the cultivars.The greatest stem diameter was seen in S.C704 and its least amount in Waxy under the salty conditions.In an experiment done by Hussain there was shown that saltiness reduces the plant height, leaves number, length of cob, grains number and the total grains number in the ear [8].As compared to the normal conditions, saltiness reduced the ear length in all the cultivars.The greatest ear length was seen in Zaqatala, B73 and S.C704, and the least amount -in K3653/2.Similar results were reported by Blanco et al.They showed that salinization reduces dry masses of ear, leaves, stems and the whole plants significantly [4].The salty condition is known to cause the decrease in water absorption by plants.For example, an experiment done for the purpose of determining the relation between water and tomato plant, showed that irrigating the plant with the salty water caused decrease of both the plant growth and the amount of absorbable water [14].Ear diameter was also reduced due to the saltiness.Under normal conditions, the least amount of ear diameter was found in S.C302 that significantly differs from the other cultivars.The least amount of the ear diameter was seen in K3653/2 (table 1).
The greatest ear mass was found in S.C704 that didn't have any significant difference with Zaqatala and B37.Together with the investigation of vegetative growth under salty conditions, some yield parameters are also studied.The most important parameters are plant height, stem diameter, and yield characteristics of the plants [3].Salinization caused reduction in the number of rows in an ear and the number of grains in a row (table 2).Weight of 100 grains was decreased because of the salinization.The greatest weight of 100 grains was recorded in Zaqatala cultivar and its least amount was seen in K3653.2.Dry mass of the plant was also decreased and the greatest dry mass was found in S.C704 that didn't have any significant difference with B73, K3653.2,S.C704, and K3615.1 cultivars.Hussain et al showed that increase in saltiness level had caused decrease in maize height, stem diameter, leaves numbers, leaf areas and dry mass of the plant [7].As compared to the normal environment, under salty conditions yield of cultivar grains was decreased.S.C704 bears the greatest grain yield and under salty conditions and K3615.1 had the least grain yield (table 2).
Correlations between the characteristics under both normal and salty conditions are presented in tables 3 and 4.Under normal conditions there was a significant and positive correlation between the plant height and ear length, and the number of grains in a row.A positive and significant correlation was seen among the stem diameter and ear diameter, and the number of grains in a row.

Table 3 Simple Correlation between Crop Yield and Some Growth Characteristics under Normal Conditions
Significant difference at the 0.05 significance level; ** significant difference at the 0.01 significance level. *