In recent years, drought stress was strongly affected on the development and yield of tomatoes. There are increasing interests in the study of physiological transformations in adaption to stress in plants In this study, effects of drought stress (mannitol at different concentration) on the development of tomato shoot were studied. Morphological and physiological changes during the development of shoot under drought stress conditions were analyzed. Based on the analysis results, the combination of cytokinin and gibberellin was treated to increase the drought stress tolerance of plants. Results showed that mannitol at 20 g/L induced tomato drought stress. Shoot height, number of leaves, leaf area, and the number of roots significantly decreased in the drought stress condition compared to the control. The formation superoxide (O2-) and hydrogen peroxide (H2O2) occurred in the meristem, elongation region and cap of the roots in the drought stress condition instead of only cap root in the control. In the drought stress condition, there was an increase in respiration intensity, proline and carotenoid content, and abscisic acid activity. In contrast, the content of chlorophyll, photosynthesis intensity, cytokinin and gibberellin activity decreased in comparison with the control. The combination treatment of zeatin 0.5 mg/L and GA3 0.5 mg/L improved the drought stress tolerance of plants. The shoot height, number of leaves, leaf area and number of roots of the treated plants were higher than those of the control plants.
In this study, NaCl at varrious concentrations of 4 – 10 g/L was used to investigate the salt tolerance of in vitro shoot cuttings of Chrysanthemum indicum. Morphological, physiological and biochemical changes during the response of shoot cuttings in the salinity stress were analyzed. NaCl at 6 g/L reduced the development of shoot cuttings. Under salinity stress conditions, there have just a little reduction of the chloroplast in parenchymal cells near the midrib of leaf before they turn brown and die. Besides, carotenoid, starch content, and photosynthesis intensity were decreased. In contrast, respiration rate, proline and total soluble sugar content, and the activity of IAA and gibberellin were strongly increased. The application of IAA 0.25 mg/L, zeatin 0.1 mg/L and GA3 0.1 mg/L improved the shoot development in the salinity stress condition. Shoots in MS medium supplemented with BA 0.2 mg/L, NAA 2 mg/L and NaCl 6 g/L grow better in salinity stress condition.
Fish mint (Houttuynia cordata Thumb.) is a popular medicinal plant grown primarily because of its pharmacological values. Drought stress has on the relationship between growth and physio-biochemical changes, especially flavonoid content. The impacts of various drought stress conditions on the fish mint development were investigated, including 85% of field capacity (FC), 75% FC, 65% FC and 55% FC in 14, 21 and 28 days. Agronomic, physiological and biochemical parameters during the growth of fish mint plants under drought stress conditions were assessed. According to the results of variance analysis, drought stress results in a considerable drop in the measured parameters (shoot height, leaf number, leaf area and fresh weight). Similarly, all of the above-mentioned parameters were also decreased with increasing the number of drought days. Furthermore, drought period and level caused a drop in respiration, photosynthetic rate, chlorophyll and starch content. The concentration of carotenoids and flavonoids, on the other hand, increased dramatically as drought stress periods and levels increased. In comparison to the control, the drought treatment (65% FC) in 7 days maintained the growth rate and increased flavonoid accumulation from 2.42 mg to 3.04 mg. These findings might give a scientific foundation for growing fish mint plants under drought stress to boost flavonoid content.
Chrysanthemum indicum cultivar Sakura is one of the daisy cultivars. It is beautiful, but the vase life of cutting flowers is very short. The decrease in flower quality during storage and transportation is a big problem in the flower export. In this study, the morphological, physiological, and biochemical changes during the vase life of cutting flowers were analyzed. The effects of plant growth regulators and sucrose at different concentrations on the vase life of cut flowers were investigated. The vase life of Sakura cutting flowers includes two stages: (1) the growing and blooming of flower, (2) senescence of cutting flowers. During the growing and blooming, the color of disk flowers changed from green to yellow, and the ray flowers continued to expand the dimension leading to an increase in the diameter of the head flower. The senescence of cutting flowers was initiated by the reduction of chlorophyll content in the leaf, which was located at the base. Then, the ray flowers were discolored. In the senescence stage, the respiration rate and the content of the abscisic acid of head flower increased continuously. In contrast, the water absorption, the content of starch, total sugar, salicylic acid, auxin, cytokinin, and gibberellin decreased strongly. The treatment of 10 g/L sucrose, 2 mg/L NAA, 5 mg/L BA, and 20 mg/L salicylic acid in 24 hours extended the vase life of Sakura cutting flowers and the diameter of the head flower.
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