seedling growth

In order to study the allelopathic effect of dried common saltwort plant (Salsola kali) on some crops seed germination characteristics and seedling heterotrophic growth, a study was conducted in the laboratory of agriculture and natural resources faculty in Mohghegh Ardabili University. The aquatic extract of common saltwort in three consistency (1-3 and 5 %) and control in a completely randomized basic design (CRD) was evaluated on germination percentage, speed of germination, root and shoot length and seedling dry matter of safflower, sunflower, wheat, vetch, alfalfa, barley, corn and rapeseed. The results proved the allelopathic effect of common saltwort because all the evaluated germination characteristics of the studied crops showed a significant decrease comparing to the control. Due to the allelopathic effect of common saltwort, germination and primary seedling growth of crops encountered impressive damages so that, germination percentage, speed of germination, root and shoot length,  and seedling dry matter reduction leads to  diminution of crops yield. It seems that sunflower, wheat and corn receive less damage from allelochemicals of common saltwort plant. So these crops are more recommendable in contaminated lands.

To evaluate salinity and drought stresses as experiments in a completely randomized design with three replications, the present research was conducted at the seedling stage. Plants under study were Trifolium pratense, Vicia sativa, Sanguisorba minor and Secale cereale. Salinity and drought levels applied to the seven levels of NaCl (control, 2, 4, 8, 16, 32 and 64 bar) and nine levels of mannitol (control, 2, 4, 6, 8, 10, 12, 14 and 16 bar). The results showed that root length, shoot length, root and shoot weight of seedlings were decreased with the increase of the concentrations of NaCl and Mannitol in comparison with the control treatment. Vicia sativa had the maximum length of roots and shoots among the four examined plants which were respectively 34.06 and 43.5 cm. According to the results of the present study, Vicia sativa had the highest tolerance to salinity and drought stresses while Secale cereale, Sanguisorba minor and Trifolium pratense had the minimum tolerance to salinity and drought stresses.

In order to study the effect of different green manures and nitrogen fertilizer levels on early growth characteristics, grain yield and yield components of wheat, a field experiment was conducted on Agricultural Faculty of Shahid Chamran University of Ahvaz during 2010-2011. The experimental design was split plot based on RCB with three replications. Main plot including nitrogen fertilizer (Urea) rates (i. e. 0, 50, 100, 150 kg ha-1) and sub-plot including green manures (i.e. control, millet, sesbania, amaranth, cowpea and mungbean). This study was madin two stages. First sowing and incorporated of green manures on to the soil and then, sowing of wheat crop. Results showed that, both green manures and nitrogen fertilizer levels had positive effect on early growth of wheat seedling. Effect of green manures on dry matter and LAI of wheat seedling in lower nitrogen rates were significantly more than higher nitrogen rates. Highest seedling dry matter and LAI were obtained by application of 100 kg N ha-1 along with cowpea as green manure. Application of green manures had significant effects on grain yield and yield components of wheat crop in all nitrogen rates. In ecological point of view, the best grain yield and biological yield were obtained by use of 50 kg N ha-1 along with legume green manures especially cowpea and mungbean. Therefore, since application of 100 kg N ha-1 is recommended nitrogen rate for this region, use of legume green manures especially mungbean and cowpea along with 50 kg N ha-1, in addition of achieving high qualitative and quantitative yield, amount of used nitrogen fertilizer reduced.

Allelopathic potential of wheat and genotypic variation among cultivars has been observed in several studies. An experiment was conducted using 70 wheat genotypes, in order to recognize and screening wheat cultivars with high allelopathic potential against Avena fatua and Hordeum spontaneum. Wheat genotypes sown in pot and after seedling development, they divided to different parts including leaf, stem and root. After drying four concentrations including 0, 25, 50 and 100% of water extract were studied on germination of wild barley and wild oat. For each weed germination percentage, radicle and hypocotyle length were measured. The results showed considerable variation in inhibitory potential of wheat genotypes. Among different plant parts, leaf and stem have higher allelopthic effects than root. The highest inhibitory effects on observed in Rasool, Mahdavi, Navid, Karaj1, Adl1, Gaspard, Gascogen, Arvand, Baiat and Azadi respectively against the both weeds. The results indicated that some wheat genotypes had more allelopathic potential that can be used in weed management programs. There is also, a selective inhibitory in wheat allelopathic properties.