Abstract
Magnolia wufengensis L.Y. Ma et L. R. Wang, a rare species which has been introduced and cultivated from southern China to northern China, frequently suffers from freezing injuries. To figure out the influence of ethephon (ETH) application on the cold tolerance during the natural overwintering of M. wufengensis, one-year shoots subjected to ethephon application at four concentrations (0, 700, 1000, and 1500 mg·L−1) were collected to measure the physiological and biochemical changes from September 2017 to 1 April 2018. The fall ETH application increased the freezing tolerance of M. wufengensis, and the optimum concentration for M. wufengensis was 1000 mg·L−1 (T2), which not only improved the shoot freezing tolerance by 1.4 times, but also led to a 25.0% faster cold acclimation rate and 13.7% slower de-acclimation rate. Moreover, 1000 mg·L−1 ETH delayed bud-burst in the spring by 10. 7 d, which was helpful for effectively avoiding cold spells in the spring, and improved the rates of bud survival by 47.1%. The improved freezing tolerance under exogenous ETH application was associated with an increased dehydration and accumulation of proline content. It seems that exogenous ETH application may be used on M. wufengensis grown in northern China to protect against freezing tolerance during the overwintering period.
Highlights
Magnolia wufengensis, a new Magnolia species (Magnoliaceae), was discovered in natural secondary forests growing with other native species in Wufeng county, Hubei Province, southern China [1,2].M. wufengensis has a narrow distribution range because of biological characteristics and anthropogenic disturbance, with only 2000 individuals making up the wild community [3].More seriously, fragmented habitation makes it much more difficult for M. wufengensis to be renewed under natural conditions, leaving it in a critically endangered state [3]
Compared with the seedlings under T0 (Figure 3), exogenous ethephon applications decreased both the relative growth rate (RGR) and days to growth cessation (DGC) values of M. wufengensis, and the RGR of shoot length decreased by 0.0019 mm·d−1 under T2
Days to growth cessation in the shoots of Magnolia wufengensis under ETH treatments is shown in the line graph
Summary
A new Magnolia species (Magnoliaceae), was discovered in natural secondary forests growing with other native species in Wufeng county, Hubei Province, southern China [1,2].M. wufengensis has a narrow distribution range because of biological characteristics and anthropogenic disturbance, with only 2000 individuals making up the wild community [3].More seriously, fragmented habitation makes it much more difficult for M. wufengensis to be renewed under natural conditions, leaving it in a critically endangered state [3]. A new Magnolia species (Magnoliaceae), was discovered in natural secondary forests growing with other native species in Wufeng county, Hubei Province, southern China [1,2]. M. wufengensis has a narrow distribution range because of biological characteristics and anthropogenic disturbance, with only 2000 individuals making up the wild community [3]. Fragmented habitation makes it much more difficult for M. wufengensis to be renewed under natural conditions, leaving it in a critically endangered state [3]. It is necessary and urgent to preserve and expand the geographic distribution of M. wufengensis. On the one hand, we have preserved the wild environment of Wufeng, and have bred Jiaohong No., which represents a new of cultivar with striking red flowers (Figure 1) [3]. Popular for urban greening, M. wufengensis has considerable ornamental and economical value owing to its colorful flowers (pure, dark, or pale red) and varied flower petal numbers (9–25, 32, or 46) [4]
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