State Key Laboratory of Desert and Oasis Ecology, Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, Xinjiang, China.
Xinjiang Key Laboratory of Conservation and Utilization of Plant Gene Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, Xinjiang, China.
BMC Plant Biol. 2023 May 16;23(1):257. doi: 10.1186/s12870-023-04245-4.
Wild apple (Malus sieversii) is under second-class national protection in China and one of the lineal ancestors of cultivated apples worldwide. In recent decades, the natural habitation area of wild apple trees has been seriously declining, resulting in a lack of saplings and difficulty in population regeneration. Artificial near-natural breeding is crucial for protecting and restoring wild apple populations, and adding nitrogen (N) and phosphorous (P) is one of the important measures to improve the growth performance of saplings. In this study, field experiments using N (CK, N1, N2, and N3: 0, 10, 20, and 40 g m yr, respectively), P (CK, P1, P2, and P3: 0, 2, 4, and 8 g m yr, respectively), N20Px (CK, N2P1, N2P2, and N2P3: N20P2, N20P4 and N20P8 g m yr, respectively), and NxP4 (CK, N1P2, N2P2, and N3P2: N10P4, N20P4, and N40P4 g m yr, respectively) treatments (totaling 12 levels, including one CK) were conducted in four consecutive years. The twig traits (including four current-year stem, 10 leaf, and three ratio traits) and comprehensive growth performance of wild apple saplings were analyzed under different nutrient treatments.
N addition had a significantly positive effect on stem length, basal diameter, leaf area, and leaf dry mass, whereas P addition had a significantly positive effect on stem length and basal diameter only. The combination of N and P (NxP4 and N20Px) treatments evidently promoted stem growth at moderate concentrations; however, the N20Px treatment showed a markedly negative effect at low concentrations and a positive effect at moderate and high concentrations. The ratio traits (leaf intensity, leaf area ratio, and leaf to stem mass ratio) decreased with the increase in nutrient concentration under each treatment. In the plant trait network, basal diameter, stem mass, and twig mass were tightly connected to other traits after nutrient treatments, indicating that stem traits play an important role in twig growth. The membership function revealed that the greatest comprehensive growth performance of saplings was achieved after N addition alone, followed by that under the NxP4 treatment (except for N40P4).
Consequently, artificial nutrient treatments for four years significantly but differentially altered the growth status of wild apple saplings, and the use of appropriate N fertilizer promoted sapling growth. These results can provide scientific basis for the conservation and management of wild apple populations.
野苹果（Malus sieversii）在中国属于二级国家保护植物，是全世界栽培苹果的直系祖先之一。近几十年来，野苹果树的自然栖息地面积严重减少，导致幼苗数量减少，种群难以再生。人工近自然繁殖对于保护和恢复野苹果种群至关重要，而添加氮（N）和磷（P）是提高幼苗生长性能的重要措施之一。本研究采用 N（CK、N1、N2 和 N3：分别为 0、10、20 和 40 g m yr）、P（CK、P1、P2 和 P3：分别为 0、2、4 和 8 g m yr）、N20Px（CK、N2P1、N2P2 和 N2P3：N20P2、N20P4 和 N20P8 g m yr）和 NxP4（CK、N1P2、N2P2 和 N3P2：N10P4、N20P4 和 N40P4 g m yr）处理（共 12 个水平，包括一个 CK），连续四年进行野外实验。在不同养分处理下，分析了野苹果幼苗的嫩枝性状（包括四个当年生茎、十个叶片和三个比值性状）和综合生长性能。
N 加显著促进了茎长、基径、叶面积和叶干质量的生长，而 P 加仅对茎长和基径有显著促进作用。N 和 P 的组合（NxP4 和 N20Px）处理在中等浓度下明显促进了茎的生长，但在低浓度下 N20Px 处理表现出明显的负效应，在中高浓度下表现出正效应。在每种处理下，随着养分浓度的增加，比值性状（叶强度、叶面积比和叶茎质量比）下降。在植物性状网络中，养分处理后基径、茎质量和嫩枝质量与其他性状紧密相连，表明茎性状在嫩枝生长中起着重要作用。隶属函数表明，单独添加 N 后，幼苗的综合生长性能最大，其次是 NxP4 处理（除 N40P4 外）。
因此，人工养分处理四年显著但不同地改变了野苹果幼苗的生长状况，适当的氮肥促进了幼苗的生长。这些结果可为野苹果种群的保护和管理提供科学依据。
