Crop production will need to increase by about 60% to satisfy the demand of food for the fast-growing population globally. A number of recent studies have provided strong support demonstrating that improving the photosynthetic efficiency via different systems can provide an avenue to improve yield potential of crops. Photosynthesis a regulated system that drives biological processes including crop yields. Hence, this review focuses on improvement of the efficiency of photosynthesis via different mechanisms; decreasing photorespiration, transforming C3 crops to C4 pathway, optimization of Calvin Benson cycle / Rubisco, and electron transport. Further work should be done on transgenic crops with modified photosynthesis. Optimization of the activity of Rubisco may not be successful in some moisture stress areas, and consideration of photoprotection could offer some advantages. Optimization of source-sink relationship would represent another promising way to improve crop yield. A strong sink can increase crop yield even under stress conditions.

The present study elucidates the effect of matrix priming with vermicompost (VCP) on germination and seedling emergence of two onion seed lots under drought, salt and temperature stress conditions. Seeds treated with water was considered as hydropriming (HP) and untreated (NP) seeds were taken as control. Treated and untreated seeds were exposed to different levels of drought (10 and 15% PEG), salt (50 and 100 mM NaCl) and temperature (30 and 35°C) stresses. Priming with vermicompost improved the performance of onion seed as indicated by higher germination and seedling growth under stress conditions. Catalase, superoxide dismutase and ascorbate peroxidase activities were found to be significantly (P < 0.05) higher in the vermicompost treated seeds than hydroprimed and untreated seeds.

Onion (Allium cepa L.), a member of the family Amaryllidaceae, is the second most widely cultivated and oldest crop used as vegetable, spice and medicinal values. It is produced in many countries where China, India and Egypt being the top three producers. It is used as cousins and value addition for different dishes across the world. Onion is also produced and marketed under medium and small scale in urban and peri-urban areas of developing countries and is used as an income generating crop that improves the livelihoods along the value chain. However, because of its perishable nature, it is subjected to significant postharvest losses. Therefore, it is worth to know some preharvest production practices, and postharvest treatment and handling methods so as to produce best quality onion bulbs and maintain the quality for a relatively longer storage periods. Nutrient management, irrigation frequency and water requirement, use of growth regulators, harvest maturity and curing methods are vital factors to produce best quality onion bulbs and maintain the quality with minimum postharvest losses. The application of these practices will contribute in the production of quality bulbs and enhance their storability

Abiotic stresses are serious problems that hinder crop production. Seed germination and seedling development are stages which are sensitive to abiotic stress. Seed priming improves the performance of seeds/seedlings and provides faster and synchronized emergence under stress conditions. The present study aimed to investigate the effect of priming with biostimulants, vermicompost (5%), karrikinolide (10-7 M) and seaweed (5%) using the solid matrix method (5 days, dark, 15 °C, 2:1:3, seed:vermiculite:organic solution, w:w:w) on germination and seedling quality of carrot seeds under abiotic stress conditions. Biostimulants were used alone and in double and triple combinations. Drought stress was simulated by PEG-6000 (-0.3 MPa), salinity by using NaCl at 100mM, and high temperature by 30 °C. Dry control and distilled water treated were used as controls. Priming treatment with biostimulants improved performance of seeds and seedlings, though not always significantly (p=0.05). Seaweed alone and its combination with karrikinolide showed the best performance for all the parameters. The germination percentage for dry control of carrot seeds were 37, 63 and 72% in salt, drought and high temperature stresses while distilled water treated seeds had values of 74, 79 and 77%, respectively. Seeds treated with seaweed+ karrikinolide and seaweed alone had 80 and 89% germination. The same treatments stimulated seedling emergence from 57% to 84-88%, 25 to 69-76%, 71 to 85-87% under drought, salt and high temperature stress, respectively. Seedling criteria, seedling height, fresh weight, dry weight and root fresh weight were also higher with these treatments in all stress conditions. Catalase activity of treated seeds was higher for seaweed (0.400 EUg-1seed) and seaweed karrikinolide (0.411 EUg-1seed) treated seeds than for both controls (non-primed: 0.299, distilled water: 0.239 EUg-1seed). Biostimulants have potential as seed priming agents to enhance seed quality in carrots.