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  • Author or Editor: Nan Ma x
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Dwarfing rootstocks can improve the plant architecture of apple trees and increase production. Gibberellins (GAs) are crucial for plant growth and dwarfing traits. The receptor, GIBBERELLIN INSENSITIVE DWARF1 (GID1), plays an important role in the regulation pathway. However, the growth regulatory mechanism of GID1 in dwarf apple rootstock seedlings is not clear. In this study, we selected dwarf apple rootstock ‘SH6’ and its cross parents as materials to clone the GA receptor gene GID1c. There were two different sites in the alpha/beta hydrolase domain. The expression of GID1c in ‘SH6’ was lower than that in Malus domestica cv. Ralls Janet, with the decrease of GA content. We further conducted GA3 treatment and overexpression of GID1c in tissue culture seedlings of ‘SH6’, and the results showed that the expression of GID1c and biosynthesis genes increased and promoted the accumulation of hormone contents, which ultimately regulates the growth of ‘SH6’ dwarf apple rootstock seedlings. Our results suggest that GID1c may affect the plant architecture and dwarf traits of dwarfing rootstock and accelerate its application in orchards.

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The relationship between spatial and temporal dynamics of major salt ions and their toxicology is still unclear, particularly in perennial orchard fields. A seasonal soil sampling was conducted from Apr. to Oct. 2011 in a salinized orchard soil in semiarid northwest China. Soil moisture content and concentrations of total soluble salt and eight salt ions were measured every 2 weeks in the soil at 0 to 2, 2 to 5, 5 to 10, 10 to 15, 15 to 20, 20 to 25, 25 to 40, 40 to 60, 60 to 80, and 80 to 120 cm during the growing period of apple trees. Soil moisture content decreased early in the growth season (Period 1) but with increasing rainfall in the middle of growing season (Period 2 and Period 3) and reached a maximum at late season (Period 4) at all depths. Soil salt concentration increased along with soil profile, particularly in the 60- to 120-cm soil layer at all periods. The highest soil salt level was observed in Period 4. The contents of HCO3 , Ca2+, and Mg2+ were almost uniform in all soil layers, but the contents of Cl, SO4 2–, and Na+ increased with soil layer. The content of K+ decreased from the upper to the deeper layers of soil profile. The distribution of CO3 2– had a high temporal and spatial heterogeneity with soil depths and season. Analysis of the charge balance on positive and negative salt ions indicated that the horizontal movement of ions and the transfer of soil water were likely the driving factors affecting soil salinization. The movement of Na+ and Mg2+ ions in the top soil may be responsible for rhizospheric ions composition and toxin effect to restrain apple tree growth in the early growth period.

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