| Abstrakt: |
Introduction: Zinc (Zn) plays an important role in plant growth and tolerance to stress and increasing their yield, but it has been reported that zinc nanoparticles have a better role on improving the growth of plants under water stress conditions. One of the factors limiting the growth of sorghum forage plant is water stress. Studies have shown that zinc nanoparticles have a positive impact on plants response to water shortage conditions through improving photosynthesis and enzymatic activity. Therefore, this study was conducted to investigate the effect of foliar application of nanosized and non-nano zinc oxide on some physiological and forage yield of three sorghum (Sorghum bicolor L.) cultivars under water deficit condition. Materials and Methods: This study was performed at the research farm of Shahrood University of Technology in the growing season of 2018-19. The experiment was arranged as split plot factorial based on randomized complete block design with three replications. Water deficit stress treatment in two levels of 10 and 20 days irrigation interval were assigned as main plots and sub plots were the combination of the two factors; sorghum cultivars at three levels: Eresk, Speedfeed and Pegah, and foliar application of zinc in three levels of control, micro and nano-particles forms at concentration of 2 gr l.-1. Foliage spraying of Zinc was performed before flowering stage of sorghum. Sampling and measuring of sorghum pigments, leaf protein, leaf zinc contents and proline were done at flowering stage. Wet and dry forage yield of sorghum was measured at the end of growing season on the 2 squares meter in each plot. All data collected were subjected of analysis of variance (ANOVA) using MSTATC software. Significant differences between means refer to the probability level of 0.05 by LSD test. Results and Discussion: The results showed that by increasing the irrigation interval from 10 to 20 days, chlorophyll a, chlorophyll b, carotenoids, leaf protein, leaf zinc content, fresh and dry forage yield decreased significantly. The results indicated that the minimum fresh forage yield (61.48 ton/ha) and dry forage yield (12.03 ton/ha) was observed with non-application of zinc in irrigation interval of 20 days. Water deficit stress causes damage to photosynthesis pigments, stomatal conductance and finally the growth and yield of plants. The results showed that application of zinc in nano or conventional form causes a significant increase in chlorophyll a, chlorophyll b, carotenoids, proline, leaf protein, zinc content, fresh and dry forage yield under stress conditions. The highest fresh and dry forage yield were observed at the rate of 97.4 and 18.8 ton.ha-1 respectively in irrigation interval of 10 days treatment by application of ZnO nano particles. Also, the results showed that, foliar application of zinc in nano and conventional form increased fresh forage yield of sorghum by 37.58 and 32.49 percent compared with control in water deficit stress condition respectively. This can be due to the role of ZnO nano particles that can enhance the rate of photosynthesis by improving gas exchange, chlorophyll fluorescence, carbonic anhydrase activity, and enhanced proline content in plants. Results also showed that in the most of physiological and yield traits and forage yield the local Ersek cultivar was better significantly than Speed Feed and Pegah cultivars. Conclusion: The foliar application of ZnO conventional and nano particles significantly mitigated water deficit stress and enhanced photosynthesis pigments, proline, leaf protein and zinc contents as well as improved the fresh and dry yield of sorghum. [ABSTRACT FROM AUTHOR] |
