| In this work, three Chinese Kale cultivars with different maturity, including “Xiacui Chinese Kale”(Early maturing), “Qiusheng Chinese Kale”(medium maturing) and “Chihua Chinese Kale”(Late maturing)were chosen as material for hydroponic cultivation. Samping was done at the following six grow stages, before flower bud differentiation, flower bud differentiation stage, after flower bud differentiation, squaring stage, harvest stage and flowering. The quality formation and active oxygen metabolism of the three Chinese Kale varieties during the growth and development were studied. Furthermore, main nutrient distribution and active oxygen metabolism of major organs in different parts were investigated in “Chihua Kale”. The results showed that:1?The variation trend of soluble protein content in the growth and development were similar between the Chinese Kale varieties with different maturity, but the variation range was different, showing a trend of “up- down- up- down – up”. The soluble protein content was low after flower bud differentiation, but the highest at the squaring stage. The highest soluble protein content was observed in early maturing variety and the lowest in the late maturing variety. The free amino acid content of all the three Chinese Kale varieties was rapidly increased before flower bud differentiation, and peaked at flower bud differentiation stage, followed with a rapid decline after flower bud differentiation. However, free amino acid content was decreasing all the time in early variety from after flower bud differentiation stage to flowering stage, while it gradually rose in the squaring stage to reach a small peak following the rapid decline in the middle and late maturing varieties. In medium maturing of free amino acid content in different growth periods of high, early maturing variety second, and lowest in late maturing variety.2?Except the late maturing variety, which showed a decline in Vc content, during harvest period content, the medium and early maturing Chinese Kale cultivars showed gradual increase from the before flower bud differentiation stage to harvest period. In the harvest period, the content of Vc in early and medium maturing varieties were significantly higher than that of the late maturing variety, but there was no significant difference in early and middle maturing varieties.3?The content of nitrate increased gradually during the growth and development of Chinese Kale varieties with different maturity. It reached the peak after the flower bud differentiation. Unlike the middle maturity variety, in which the nitrate content increased in the picking time, other maturing varieties began to show a downward trend from the squaring stage. The highest nitrate salt content was observed in the early variety, followed by medium variety, and late maturing variety had the lowest content. The nitrite content was not significantly different from before flower bud differentiation stage to picking time.4?The changes of sugar content in the three Chinese Kale varieties were different in the growth and development process, and there were some differences in the variation range. In early maturing variety and middle maturing variety, the soluble sugar content decreased significantly from before flower bud differentiation stage to flower bud differentiation period, but it increased significantly in early maturing variety after flower bud differentiation, and such difference in middle maturing variety after flower bud differentiation was not significant. Soluble sugar content in late maturing variety in the process of growth and development showed gradually rising trend, but the difference was not significant from the before flower bud differentiation stage to squaring period. The fructose content of early maturing variety decreased rapidly before the flower bud differentiation, and increased significantly in the squaring stage, and decreased during the picking time; in medium maturing variety, it first decreased in the period of flower bud differentiation, then increased significantly after flower bud differentiation and changed little after squaring stage; in late maturing variety, it showed no obvious change before and after the flower bud differentiation period, but continuously went up after the flower bud differentiation. The sucrose content of Chinese Kale varieties showed no significant difference before flower bud differentiation to the flower bud differentiation. But in the squaring stage, it decreased significantly in the medium maturing variety. It was rising from the beginning of the squaring stage for early maturing variety and rising from after flower bud differentiation for late maturing variety.5?For early maturing variety, the highest glucosinolate content was observed in front of the flower bud differentiation, followed with a significant reduction during flower bud differentiation period. After flower bud differentiation, the glucosinolate content showed no significantly change. For medium maturing variety, the content of glucosinolate was significantly decreased at the stage of flower bud differentiation, but significantly increased and kept at a certain level after the flower bud differentiation period. In late maturing variety, the glucosinolate content in flower bud differentiation period first went down, hardly changed during flower bud differentiation, and then went up after the budding period.6?The variation of sugar metabolism-related enzyme activity were significantly different in the tree Chinese Kale varieties. The activity of neutral invertase(NI) in early and middle maturing varieties was decreased from the stage of flower bud differentiation, significantly increased in the squaring stage, and decreased rapidly after budding stage. In late maturing variety, it decreased significantly from before flower bud differentiation to flower bud differentiation, then increased significantly after flower bud differentiation period. Acid invertase(AI) activity in different maturity varieties of Chinese Kale in the process of growth and development showed a trend of gradual decline, but no significant change was observed for early and late maturing varieties in during flower bud differentiation, or for mid maturing variety from the after flower bud differentiation to squaring stage. In the early and late maturing varieties, the activity of sucruse synthase(SS) increased significantly in after flower bud differentiation stage, followed with a decrease during squaring stage, and rose again in harvest period; For medium maturing variety, SS activity showed a decline from the stage of flower bud differentiation to the squaring stage, followed with an increase, after the squaring period. For all varieties, the sucrose phosphate synthase(SPS) activity decreased significantly from before the flower bud differentiation to flower bud differentiation period. However, in early and middle maturing varieties, it increased after flower bud differentiation, declined during squaring stage decline, and then continued to rise after the squaring period, For the late maturing variety, it continued to riseafter the flower bud differentiation period.7?There were some differences in the changes of cell protective enzyme activities during the growth and development of Chinese Kale varieties with different maturity. Superoxide dismutase(SOD) activity of early maturing variety decreased significantly before the flower bud differentiation, increased from the stage of flower bud differentiation to the squaring stage, and decreased during the harvest period. In medium and late maturing varieties, SOD activity showed no obvious change from before the flower bud differentiation to flower bud differentiation period, rapidly went up after flower bud differentiation period and remained relatively at a stable level. In early maturing variety, the peroxidase(POD) activity did not change significantly before and after flower bud differentiation, increased significantly in the squaring stage and significantly decreased at harvest time. For middle maturing variety, POD activity showed no obvious change at different growth stages. In the late maturing variety, POD activity increased rapidly in the flower bud differentiation period and then decreased in the following period. In early maturing variety, the activity of catalase(CAT) did not change significantlyfrom before flower bud differentiation stage to flowering period; In middle maturity variety, no obvious change in CAT activity was observed in flower bud differentiation stage. In contrary, CAT activity in late maturing variety, were significantly increased, After flower bud differentiation stage, the change in early and late maturing varieties were not significant.8 ? In early and middle maturity varieties, proline(Pro) content in flower bud differentiation period increased significantly. However, Pro content showed a rapid declinein early maturing variety after flower bud differentiation, maintained at certain level until squaring period, and went up during harvest period. In middle maturing variety, Pro continued to rise from after flower bud differentiation to flowering period. For the late maturing variety, Pro content did not change significantly from before flower bud differentiation to squaring period, and rose from the budding period. Malondiadehyde(MDA) content in early and middle varieties did not change significantly in flower bud differentiation period, after flower bud differentiation was significantly increased, but did not change significantly after squaring stage; In late maturing variety, the content of MDA did not change significantly in growth and development.9?The contents of nutrients and the level of active oxygen metabolism exhibited remarkable differences among different organs and different parts of the same organ. In general, the content of soluble sugar, fructose, sucrose and free amino acids gradually reduced from top to the bottom parts of the same organ. Among different organs, the contents of soluble sugar, fructose, sucrose and free amino acids were found highest in flower stalk stem, followed with petiole and leaf. The content of nitrate and nitrite gradually increased from top to the bottom parts of the same organ. Among different organs, the contents of nitrite were the lowest in flower stalk stem and relatively high in petiole and leaf. Different parts of the same organ, changes of glucosinolate content trend of bolting stem, leaf and petiole were similar, both top>middle>bottom,the glucosinolate content in flower stalk stem is the highest, followed by petiole and the lowest in leaves. The activities of SOD, POD and CAT gradually decreased, and MDA content gradually increased from top to the bottom parts of the same organ. The highest level of SOD and POD activities were found in flower stalk stem and lowest in leaf. However, leaf had the highest CAT activity and MDA content. Based on these results, it can be clearly seen that the upper parts of kale and the flower stalk stem had the highest level of nutrients and the best edible safety. Along with the prolonged physiological age of kale plants, the active oxygen species-scavenging capability gradually decreased and the membrane lipid peroxidation gradually increased. Among different organs of Chinese kale, active oxygen species-scavenging capability was found highest in flower stalk stem, and lowest in leaf. |
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