Hot pepper (Capsicum annuum cv. Battle) was grown in a 1:1 v/v sand-to-cotton stalk compost and subjected to four irrigation treatments: 100% of water-holding capacity (control) and 85%, 70%, and 55% of water-holding capacity, which were considered deficit irrigation treatments. All treatments were given to the plants at the first day of transplanting and continued during the whole growing season. Our results demonstrated that deficit irrigation had a negative effect on plant growth and yield. Increasing irrigation deficiency exhibited a reduction in vegetative growth, fruit parameters, and yield and a nonsignificant increase in irrigation water use efficiency and a corresponding reduction in the amount of irrigation water. Vitamin C content in fruit was significantly decreased by deficit irrigation treatments at various ripening stages. Water-holding capacity of 100% and 85%, respectively, resulted in the highest content of vitamin C obtained at the ripening stage. We concluded that ‘Battle’ hot pepper is sensitive to deficit irrigation. Supplying this cultivar with water at 85% of water-holding capacity could be a practical irrigation technique for high value of vitamin C production as well as saving a large amount of water, which outweighs the decrease in total fresh yield of fruit, especially in areas suffering from water shortage.
The application of plant growth regulators (PGRs), such as abscisic acid (ABA), putrescine (Put), and 2,4-epibrassinolide (EBR), has been shown to enhance a plant's resistance to various abiotic stresses. However, the protective effects of these PGRs on tomato (Solanum lycopersicum) seedlings under suboptimal temperature stress have not yet been evaluated. We also do not know the most effective method of application of PGRs for various tomato cultivars. We studied the effects of three rates of exogenous ABA, Put, or EBR in limiting damage from suboptimal temperature stress on two tomato cultivars, Zhongshu6 (considered sensitive to suboptimal temperatures) and SANTIAM (considered tolerant to suboptimal temperatures). Results showed that application of these PGRs at appropriate concentrations could effectively reduce the decline in the net photosynthetic rate (Pn) and the chlorophyll (Chl) content in leaves caused by suboptimal temperature stress in both ‘Zhongshu6’ and ‘SANTIAM’ and could promote an increase in organic osmolyte (proline and soluble sugar) contents and root 2,3,5-triphenyltetrazolium chloride (TTC)-reducing activity for ‘Zhongshu6’. However, these effects were inferior on ‘SANTIAM’. For both cultivars, the best treatment concentrations are 1 mm ABA, 0.1 mm Put, or 0.02 μM EBR. Results indicate that in tomato production, exogenous application of ABA, Put, or EBR at appropriate concentrations can effectively limit damage from suboptimal temperature stress.