To understand the mechanisms causing yield limitations in defoliated plants subjected to water deficiency, the experiments were laid out as a randomized complete block design with split-plot arrangement. Soil-water regimes consisted of moderate irrigation until physiological maturity (W 1 ) or short severe water stress periods (W 2 ) at V 8 stage of ontogenesis, and tasseling which allotted to the main plots. Defoliation times (V 8 and tasseling) and intensities (cutting of one or two thirds of leaf blade) combinations and one control level (five Source restriction treatments) were allotted to subplots. Early defoliation caused reduction in grain yield at W 1 and W 2 by 19.2 and 14.8%, respectively. On the other hand, water deficiency reduced grain per ear by 23.9% and increased individual grain weight by 37.0% (plasticity of sink capacity). These results show that under water deficiency, grain yield limitation was mostly due to a reduction in dry matter allocation to grains (sink capacity) than a result of lower dry matter production (source strength). Findings suggest that in non-irrigated corn, breeders must direct their selection program to increase grain set and decrease surplus leaves.

Background: Grass pea (Lathyrus sativus L.) is a crop of immense economic significance. It is one of the most resilient to climate changes and to be survival food during drought-triggered famines. Methods: In a field study split factorial experiment based on a randomized complete block design with 3 replications were used, effects of irrigation regimes (50, 75 and 100% evaporation of Pan class A) and different rates of phosphorous fertilizer (triple superphosphate 0, 60 and 120 kg/ha) on growth and yield of two grass pea ecotypes (Lalehzar and Sharekord) in Lalezar area (Kerman province, Iran) was carried out during 2018 and 2019. Result: The results showed that drought stress reduced grass pea seed yield (401 kg/ha-1) and biological yield (863 kg/ha-1) and this reduction was depended on the severity of stress. In the other side, application of phosphorous fertilizer (60 kg/ha-1) increased grass pea yield (2401 kg/ha-1). This means that phosphorus fertilizer could partiaiiy offset the effect of drought stress and had a significant effect on the water use efficiency and phosphorus agronomic efficiency. Finally, drought stress, either no-application phosphorus fertilizer, could decrease yield. Overally, Shahrekord ecotype showed the higher and most desirable grain yield (2401 kg/ha-1), biological yield (5612 kg/ha-1), grain water use efficiency and biological water use efficiency, respectively, with (0.74 and 1.72 m3 water/ha-1) and phosphorus agronomic efficiency (18.76 kg yield/kg P) to the applied treatments (75% irrigation+ triple superphosphate fertilizer 60 kg/ha).

SUMMARYReproductive development and growth stages of crops are especially important for seed production and affect seed quality. In order to evaluate the effect of planting date via canopy temperature during reproductive growth stages on soybean seed germination and vigor, an experiment was conducted at two locations, experimental farm of seed and plant certification and registration institute in Karaj and experimental farm of agricultural and natural resources center of Moghan, Ardabil, Iran, in 2013

The present work aimedto establish a morphological characterization of 10 sorghum (Sorghum bicolor L. Moench) cultivars sampled from farmers of OuedRigh valley. The study wasbased on the evaluation of 20 agro-morphological parameters of which 14 are quantitative and 6 qualitative.Principal components analysis (ACP) of the results suggested interdependence of evaluated parameters and showedsignificant differences amongcultivars. The study revealed eight highly significant correlations, including four positive and four negative. The cultivars of the Blidet Amorregion, Bouhnik"BA1"and Mahjoubi "BA3",and the cultivar of the Nezla region, Boucetta "N4" expressed the best values for the number of tillers, the length of the seed and the weight of 1000 seeds.