In this issue, we bring you the effects of 5-ALA on the growth index and antioxidant enzyme activity of cucumber. Let's get started without further ado

　　01 Materials and methods

　　02 Results and analysis

　　Effects of exogenous ALA on growth indexes of cucumber

　　Effect of exogenous ALA on dry and fresh quality of cucumber seedlings

　　It can be seen from the above figure that the changes of dry and fresh quality of different cucumber varieties without 5-ALA treatment are also different under different lighting conditions. The increase of dry mass under h02 shading was significantly lower than that without shading, while the increase of fresh mass was significantly increased. The change trend of h082 is opposite to that of h02. The increase of dry and fresh quality of Chuanlv No. 1 under unshaded light is higher than that under shaded light.

　　Effects of exogenous ALA on plant height and stem diameter of cucumber seedlings

　　As can be seen from the above table, shading can promote the increase of plant height of cucumber seedlings, while reducing the increase of stem diameter. The thinner the stem, the more unfavorable the growth of cucumber seedlings. After application of exogenous ALA, the increase of plant height and stem thickness of cucumber seedlings increased to different degrees than that of CK, and the effect was most obvious after 1mg/L treatment, but the high concentration of ALA treatment had a tendency to reduce the plant height and stem thickness of cucumber seedlings.

　　Effect of exogenous ALA on leaf area of cucumber seedlings

　　It can be seen from the above table that the leaf area of cucumber seedlings can be effectively increased by applying a certain concentration of ALA under both shaded and unshaded conditions. Under shading, the leaf area of h02 and Chuanlu No.1 increased more significantly than CK at 1mg/L, while the leaf area of h082 increased more at 0.1 and 1mg/L. The leaf area of the three cucumber varieties increased the most at 1mg/L without shading, and h02, h082 and Chuanlu No. 1 increased 35.3%, 41.4% and 73.3%, respectively, compared with the control. With the increase of ALA treatment concentration, the leaf area under shading and unshading had a decreasing trend.

　　Effect of exogenous ALA on antioxidant enzyme activity of different cucumber varieties

　　Effects of exogenous ALA on MDA content in cucumber leaves

　　It can be seen from the above figure that applying exogenous ALA can reduce MDA content in cucumber seedling leaves. FIG. 1 shows that on the second day after ALA application, MDA content in cucumber leaves treated with 5 concentrations decreased, among which the effect of 1mg/L treatment was more prominent, and the content of MDA in 3 cucumber varieties decreased by 13%, 45% and 24% compared with CK, respectively. Figure 2 shows that the 6dMDA content of h02 and h082 under shading mostly increased after treatment, but the increase rate decreased compared with CK. On the sixth day of 1mg/L treatment, the content increased the most compared with other treatments, 24% and 44% respectively. Chuanlv No.1 decreased significantly compared with CK at 0.1 and 1mg/L, but other effects were not obvious. The MDA content of h02 and h082 increased significantly, while the change of Chuanlu-1 was not significant, indicating that Chuanlu-1 had low degree of lipid peroxidation and little cell membrane damage, and low light had little effect on it.

　　Effects of exogenous ALA on SOD activity in leaves of different cucumber varieties

　　As can be seen from Figure 3, SOD activity of h082 and Chuanlu 1 increased by about 50% and 25% compared with CK on the second day after 1mg/L ALA treatment of the three cucumber varieties under unshaded conditions, and h02 had little change. As can be seen from FIG. 4, under the shading condition, SOD activity of cucumber seedlings after application of exogenous ALA2d was higher than that of CK, and in the treatment of 5 concentrations, the effect was most obvious when exogenous ALA concentration of 1mg/L was applied during the whole treatment period.

　　Effects of exogenous ALA on SOD activity in leaves of different cucumber varieties

　　As can be seen from FIG. 5, when exogenous ALA is applied without shading, the concentration of 1mg/L has the best effect. 6 days after treatment, the POD of h02 and h082 increases by 39% and 27%, respectively, compared with CK, while the other concentrations of ALA have little difference with CK after application. There was no significant change in POD activity of Chuanlu-1 after applying ALA. As can be seen from FIG. 6, the activity of h02POD treated with 0.1 and 1mg/LALA showed a trend of increasing, and was slow in the later stage. On the 6th day after treatment, the POD activity of 1mg/LALA was increased by 40% compared with CK. The treatment of h082 and Chuanlu-1 showed a trend of first increase and then decrease, and the POD activity of Chuanlu-1 decreased significantly, indicating that Chuanlu-1 was relatively more resistant to low light and could better adapt to low light environment. Overall, the effect was most obvious when 1mg/LALA was applied.

　　In this period, cucumber was used as a test material to deeply study the effects of exogenous ALA on the growth indexes and antioxidant enzyme activities of cucumber. The results showed that: Exogenous ALA with a certain concentration can improve plant growth, enhance POD and SOD activities, reduce MDA content, alleviate low light stress of cucumber to a certain extent, and improve plant vitality, and the best effect is 1mg/L ALA treatment. This result, combined with our previous articles, can once again confirm a conclusion: 5-ALA has a very significant function of stress resistance, so the amount of it can be reduced accordingly during application (such as irrigation and fertilization), and the cost of fertilizer can be better controlled.