Effects Of Six Plant Growth Regulators On Growth And Development Of Tobacco Seedlings

In this experiment,tobacco variety NC102 was used as the experimental material,and polytropin-azole,indolebutyric acid,naphthyl acetic acid,kinetin,gibberellin and 6-BA were selected.The dynamic changes of agronomic characters,photosynthetic characteristics,chlorophyll parameters and other indexes of tobacco seedlings were measured to investigate the effects of six plant growth regulators on morphological indexes,photosynthetic indexes and physiological indexes of tobacco seedlings,and to provide a basis for the rational use of six plant growth regulators in floating tobacco seedlings.The main results are as follows:1.Effects of six plant growth regulators on the growth characteristics of tobacco seedlingsThe application of six plant growth regulators in hoagland nutrient solution had certain effects on the growth and development of tobacco seedlings.At the appropriate concentration,all the six plant growth regulators could reduce the plant height,increase the stem diameter,increase the dry weight of root and shoot,and improve the seedling index.The results showed that the indobutyric acid treatment of 0.4 mg/L had the best effect,and the dry weight of root system increased by 6.94%⁹7.44%,and the seedling index increased by 6.25%¹09.96%.2.Effects of six plant growth regulators on photosynthetic characteristics of tobacco seedlingsPlant growth regulators of different concentrations also had certain effects on SPAD value and photosynthetic system of tobacco seedlings.The net photosynthetic rate?Pn?,transpiration rate?Tr?and stomatal conductance?Gs?of leaves first increased and then decreased with the increase of growth regulator concentration,while the intercellular CO₂concentration?Ci?first decreased and then increased with the increase of growth regulator concentration.The study found that 0.2 mg/L polytropisole treatment had the best effect,and there were significant differences between the Pn,Tr and Gs values of leaves and the control group,which increased by 63.33%,43.53%and 103.06%,respectively.The Ci reached the minimum value,which was 112.18%lower than the control treatment.3.Effects of six plant growth regulators on physiological characteristics of tobacco seedlingsPlant growth regulators at different concentrations had different effects on the content of protective enzymes and malondialdehyde in tobacco seedlings.The results showed that the application of 0.4 mg/L kinase had the best effect,and the activities of SOD,POD and CAT reached the maximum,which were significantly different from the control group,with the increase of 81.66%,32.64%and 55.95%respectively,while the content of malondialdehyde?MDA?reached the minimum value,which was significantly reduced by 51.16%compared with the control group.The results showed that the optimal concentration of naphthylacetic acid and kinetin was0.2 mg/L.Based on the physiological characteristics of tobacco seedlings,the optimal concentration of naphthylacetic acid and kinetin was 0.4 mg/L.Compared with the control group,0.2 mg/L prilotrozole and gibberellin had the best overall effect and the highest seedling index.When indolebutyric acid and 6-BA were applied at a concentration of 0.4 mg/L,the effect of promoting root development was the most obvious.