Effects Of La On The Yield, Quality And Physiological Indicators Of Grafted Watermelon

The paper studied the application of rara earth element La in grafted watermelon production. Watermelon(Citrullus lanatus) cultivars "Heifeicui" and "Jinshuai" on the foliage at straw period, incipient blooming period and fruit expansion period were sprayed with 0,60,120,180 and 240 mg/L of La(NO3)3 solution. The yield, quality and physiological indicators of grafted watermelon leaf were studied. The main results were as follows:1. The 120 mg/L concentration of La³⁺ could increase the contents of chlorophyll and photosynthetic rate in different genotypes grafted watermelon leaf. The 240 mg/L concentration of La³⁺ could decrease the contents of chlorophyll and photosynthetic rate in different genotypes grafted watermelon leaf.2. La³⁺ could regulate antioxidant system in different genotypes grafted watermelon. The 120 mg/L concentration of La³⁺ was used for regulating the activities of SOD and POD in different genotypes grafted watermelon, decreasing MDA content and cell membrane permeability, improving the biological properties and adversity resistance of grafted watermelon, delaying senescence of leaf and keeping photosynthetic performance of functional leaves.3. Low concentration La³⁺ increased the yield and fruit quality of grafted watermelon. Effects of high concentration La³⁺ were on the contrast of those. The 120 mg/L concentration of La³⁺ could increase the per plant fruit setting number, single fruit weight yield and fruit quality little, but make the yield and fruit quality of grafted watermelon decreased.4. The 120 mg/L concentration of La³⁺ was beneficial to the growth of different genotypes grafted watermelon and decreasing the activities of AAO and PPO in functional leaves, which lead consumption of respiration decreased. But it was favorable for the accumulation of photosyn - thetic products and transport in fruits. The 120 mg/L concentration of La³⁺ could decrease the activities of PAL in growth grafted watermelon functional leaves.5. The most suitable concentration of La³⁺ is 120 mg/L for different genotypes grafted watermelon. The concentration of La³⁺ which is higher than 180 mg/L could was detrimental to genotypes grafted watermelon.