Effects of methionine-selenium added in soil on physiological characteristics and quality of muskmelon

【Objectives】This paper explored the regulation functions on the growth and physiological characteristics and the enrichment effect of selenium (Se) in muskmelon (Cucumis melo) with methionine-selenium (Met-Se) treatment, as well as the variation trend of soil Se. 【Methods】 In this study,the effects of Met-Se on the growth, yield, photosynthesis characteristics, quality and Se content of the muskmelon ‘M135’, as well as the effects of total Se content in different tissues and organs, and the variation trend of different forms of Se in soil were determined by the method of adding Met-Se into the soil to make soil Se content to 4, 10 and 16 mg/kg respectively, with a pot experiment, soil without Met-Se as control. 【Results】 The treatments with 4, 10 and 16 mg/kg Se all could lead to an obvious increase in pigment content, photosynthetic rate, growth and yield, and the contents of organic and inorganic Se, soluble sugar, protein, free anomic acid and vitamin C in fruit. Especially, 10 mg/kg Se treatment has the best effect on the quality of muskmelon fruit. For example, the yield of per plant of 10 mg/kg Se treatment was increased by 19.53% compared with control, and the contents of soluble sugar, protein, free anomic acid and vitamin C in treatment fruit increased by 14.82%, 49.88%, 23.42% and 25.03%, respectively. Additionally, the content of organic Se in muskmelon sarcocarp was 36.87 μg/kg, which was about 82.91% of total Se(44.74 μg/kg)and met the selenium-rich standard. Further study found that, although the activity of nitrate reductase, the content of nitrate and nitrite in sarcocarp were raised with the increasing of soil Se concentration, the content of nitrite in 4, 10 and 16 mg/kg Se treatments sarcocarp were 1.499, 1.907 and 2.131 mg/kg, respectively, and were far below the national standard limit(20 mg/kg). In this study, the contents of Se in different tissues and organs, including root, stem, petiole, leaf, pericarp, sarcocarp and seed were raised with the increasing of soil Se concentration. In addition, the Se concentration in leaf was higher than in root, stem and petiole when soil without Met-Se added. While the root has the highest Se content when adding Met-Se into the soil, following was stem, leaf and petiole. Furthermore, the seed has higher Se concentration than sarcocarp and pericarp with or without Met-Se treatment. In the upper soil, the content of total Se and inorganic Se6+ was decreased after planting without application of Met-Se, while the contents of organic Se and inorganic Se4+ has no significant changing. In the soil with adding 4, 10 and 16 mg/kg Met-Se, the contents of organic Se, total Se and inorganic Se4+ were all reduced after planting, while the content of inorganic Se6+ was firstly increased, and then decreased. 【Conclusions】 The Se utilization rate of muskmelon was lower by adding Met-Se into soil, but it had improved the Se content of the muskmelon sarcocarp, enhanced the photosynthetic capacity, promoted the growth, as well as improved the yield and integrated quality, and the optimum concentration of Se for soil was 10 mg/kg.