Drought is still limited in most crops is produced. Morphological and physiological knowledge to improve drought resistance under drought conditions created problems important is the fact each of these genetic relationships and processes associated with the exact amount of important plant and grain yield is unknown. The other hand, heritability of grain yield under water is reduced. Improve the performance of drought tolerant cultivars based on morphological and physiological components of plant modification as an important solution is proposed. One of the key predictions of climate change is that, in some regions, droughts are likely to increase in frequency and severity. This will have significant implications for the long-term viability of plant populations, especially where water availability plays a key role in delineating species ranges. However, while drought and overall aridity are known to be strong determinants of plant species distributions at the landscape level, much less is known about the ways in which plant populations respond to changes in drought regime, or the long-term impacts that extreme droughts have on plant community composition, structure, and function. While it is known that drought can cause significant re-structuring of plant communities, relatively few studies have quantified the environmental and biological factors that promote plant survivorship under acute moisture stress, especially in topoedaphically heterogeneous landscapes. The capacity for evolution to rescue plant populations faced with increasingly severe drought from extinction is also poorly understood. This places severe restrictions on our ability to predict the impacts of climate change on plant populations in many environments worldwide. In this paper a review Effects of climate change and Drought-stress on plant physiology.

Improved product quality, sustainable cultivation systems, and reduced production costs are among the objectives of modern agriculture despite the global and local climate changes that have faced crops with a variety of stresses. Biostimulants seem to be capable of helping plants in their struggle against these stresses toward the goals of modern agriculture. These compounds include humic substances, seaweed extracts, amino acids, microbial inoculants, and minerals such as useful elements and inorganic salts including phosphates and antiperspirants. While application of biostimulants has witnessed a dramatic increase in the world and in Iran over the past few years, it must be noticed that they might have different effects on different species and even on different varieties of a given plant species. Their application for agricultural and horticultural purposes must, therefore, be duly modified in accordance with local and regional research findings. It is the objective of this paper to provide a better understanding of plant biostimulants based on scientific findings and practical experience in agriculture and horticulture. It will be shown that plant biostimulants are capable of improving crop production, enhancing plant resistance to abiotic stresses, and elevating crop quality. Future research in this area should aim at the determination of the mechanism(s) underlying the activities of such materials since a better understanding of their activities and effects will be necessary for achieving sustainable agricultural production systems.

Phytoremediation of lead using plants in lead-contaminated soils is a new and safe environmental technology. By adding chelators and increasing plant extraction, the efficiency of this technology can be increased. In this regard, we evaluated the effect of adding EDTA chelates to lead-contaminated soils to investigate the amount of lead accumulation in a medicinal plant, Calendula officinalis. We designed a factorial experiment in the form of a completely randomized, with three replicates in pots and two factors including EDTA at two levels (0, 50 mg kg-1) and lead at four levels (0, 30, 90, and 270 mg kg-1). In this plant, the accumulation of lead was accompanied by an increase in the amount of lead in the soil due to the addition of EDTA to the soil. The results showed that EDTA significantly increased the lead translocation of lead from roots to the aerial part of the plant.Total Chl. and shoot dry weight decrease significantly in EDTA treatment than control specific at a high level of Pb in the soil. Also, the results showed that EDTA increased lead removal from soil to soil solution and increased lead translocation from roots to the aerial part of the plant of Calendula officinalis. In general, the results of this research showed that with the careful management and EDTA use in lead extraction, it has provided a cost-effective and safe environmentally strategy.