不同种源油松幼苗的光合色素和非结构性碳水化合物对模拟氮沉降的短期响应

以不同种源(内蒙NM、北京BJ和山西SX)的3年生油松幼苗为研究对象,研究不同种源油松幼苗的光合色素以及非结构性碳水化合物(NSC)对氮沉降增加的短期响应。实验中设置5个氮处理:CK(0 kg hm-2a-1)、N1(15 kg hm-2a-1)、N2(25 kg hm-2a-1)、N3(50 kg hm-2a-1)、N4(150 kg hm-2a-1)。研究结果表明:(1)不同生长季,3个种源油松幼苗的光合色素对氮沉降增加的响应存在差异,但是只有BJ种源油松幼苗的叶绿素含量在生长季中期受到了氮沉降增加的显著促进作用,并在N4水平下达到最大值。(2)氮沉降的增加促进了3个种源油松幼苗NSC的转移和消耗,在生长季初期和中期,随着氮沉降水平的升高,3个种源油松幼苗的可溶性糖(SS)含量、淀粉(ST)含量以及总非结构性碳水化物(TNC)含量呈不同程度的降低。生长季末期,3个种源油松幼苗的SS和TNC明显积累。N4水平抑制了NM种源油松幼苗SS和BJ种源油松幼苗ST的累积,促进了NM种源油松幼苗ST含量和BJ种源油松幼苗SS含量的提高。氮沉降的增加显著抑制了SX种源油松幼苗NSC的积累,延长了幼苗的生长期,推迟了幼苗进入休眠的时间。

Short term responses of photosynthetic pigments and nonstructural carbohydrates to simulated nitrogen deposition in three provenances of Pinus tabulaeformis Carr. seedlings

Nitrogen (N) deposition has noticeably increased in China in recent years, which is expected to have influenced the physiological characteristics of Pinus tabulaeformis Carr. To improve our understanding about the effects of elevating N deposition on P. tabulaeformis, the short-term responses of the photosynthetic pigments and nonstructural carbohydrates (NSC) in seedlings with three provenances were studied. We set up a simulated N experiment with three provenances of 3-year-old P. tabulaeformis seedlings on Lingkong Mountain in Shanxi Province. The three provenances were Neimeng (NM), Beijing (BJ), and Shanxi (SX). Five N treatments with three replications were designed, including CK (0 kg hm^-2 a^-1), N₁ (15 kg hm^-2 a^-1), N₂ (25 kg hm^-2 a^-1), N₃(50 kg hm^-2 a^-1) and N₄ (150 kg hm^-2 a^-1). The source of N was NH₄NO₃ and fertilization was carried out five times in 2012. The contents of the photosynthetic pigment and nonstructural carbohydrate in the seedlings with three provenances were measured under different N treatments in June, August, and October, 2012. The results showed that: in different growing seasons, photosynthetic pigments exhibited various responses to elevated N deposition in P. tabulaeformis seedlings, regardless of provenance. In the early growing season, the photosynthetic pigment contents showed no significant response to the addition of N in any of the seedlings. In the intermediate growing season, the chlorophyll content of BJ provenance seedlings increased significantly under elevated N deposition treatments, reaching a maximum under the N₄ treatment. There was no significant increase in the chlorophyll content of provenances NM and BJ increased after adding N. In the late growing season, the photosynthetic pigment content of provenance SX was lowest under the N₁ treatment and increased under the N₂, N₃, and N₄ treatments, with no significant differences to CK. The photosynthetic pigment contents of NM and BJ provenances seedlings were not affected by N deposition. Elevated N deposition promoted the transfer and consumption of nonstructural carbohydrate (NSC) in all three seedlings. In the early growing season, N addition significantly reduced soluble sugar (SS) and total nonstructural carbohydrate (TNC) content in the NM provenance seedlings, the TNC content in BJ provenance seedlings, and the SS content in SX provenance seedlings. In the intermediate growing season, the SS, starch (ST), and TNC contents in NM provenance seedlings were lowest under the N₄ treatment. In contrast, in SX provenance seedlings, these three indexes reached minimum values under the N₃, N₁, and N₂ treatments, respectively. The SS, ST, and TNC in BJ provenance seedlings showed no significant responses to N deposition. In the late growing season, SS and TNC content noticeably increased in the seedling needles of all three provenances; however, they exhibited various responses to different N deposition levels. The TNC contents in the seedlings of NM and BJ provenances were not significantly influenced by elevated N deposition. High N deposition (N₄ treatment) inhibited SS accumulation in NM provenance seedlings, but increased SS content in BJ provenance seedlings. In addition, high N deposition clearly inhibited ST in BJ provenance seedlings, but increased ST content in NM provenance seedlings. Elevated N deposition significantly inhibited NSC accumulation in SX provenance seedlings, which delayed seedling dormancy and extended the growing period of seedlings.