Effect of arbuscular mycorrhiza on the growth of Camptotheca acuminata seedlings

Camptotheca acuminata seeds were sown in sterilized sands in the greenhouse in February of 2005. After 90-day growth, seedlings were inoculated with three species of arbuscular mycorrhizal fungi （AMF）, Acaulospora mellea, Glomus diaphanum and Sclerocystis sinuosa.. The height, biomass, and absorptions of nitrogen and phosphorus of C. acuminata seedlings inoculated with AMF were investigated. The results showed that the formation of AM promoted the height growth and biomass accumulation of seedlings significantly and improved the absorption of phosphorus in seedlings. The height and biomass of mycorrhizal seedlings were 1.2 and 1.6 times higher than those of the non-mycorrhizal seedlings. The absorption of nitrogen was less influenced by the formation of AM. The nitrogen content in mycorrhizal seedling was equal to that of non-mycorrhizal seedlings. Compared with non-mycorrhizal seedlings, the nitrogen content of mycorrhizal seedlings inoculated with A. mellea changed considerably in the root, stem and leaves. The difference in nitrogen content was not significant between mycorrhizal seedlings inoculated with G. diaphanum and S. sinuosa. The AM formation stimulated the absorption of phosphorus, especially in roots, and also changed the allocation of nitrogen and phosphorus in different organs of seedlings. Compared with non-mycorrhizal seedlings, the ratio of nitrogen and phosphorus in mycorrhizal roots increased, but reduced in stem and leaves.

Effect of Arbuscular Mycorrhiza on the Content of Nitrogen and Nitrogenous Matter in Amur Corktree Seedlings

[Objective] This study aimed to explore the effect of arbuscular mycorrhiza on the content of nitrogen and nitrogenous matter in amur corktree（Phellodendron amurense Rupr.）seedlings. [Method] The annual seedlings of Phellodendron amurense Rupr. were inoculated with four arbuscular mycorrhiza fungi in a pot experiment to study the influences of arbuscular mycorrhiza on the content of nitrogen and nitrogenous matter in Phellodendron amurense Rupr. [Result] After inoculation with arbuscular mycorrhiza fungi, the Phellodendron amurense Rupr. seedlings developed arbuscular mycorrhiza, leading to an enhancement of photosynthetic capacity. The leaf nitrogen content of those inoculated with Glomus mosseae increased to 1.28- 1.60 times as compared with the control. The chlorophyll content and chlorophyll a/b ratio were also raised, with an increase over 25% of chlorophyll a content. In addition, IAA content in plants increased to 1.65-2.41 times; and nitrate reductase activity was also enhanced, as well as soluble protein content, 1.67-2.49 times as high as the control, which improved the nitrogen metabolic ability, and promoted the plant growth, as well as the secondary metabolic ability. [Conclusion] This study provides a theoretical basis for the application of arbuscular mycorrhiza on Phellodendron amurense Rupr.

植株大小、枝龄和环境共同驱动红松枝性状的变异

许多枝性状的变异受植株大小、枝龄或环境的影响,但少有研究同时评估这些因素对枝性状种内变异的重要性。该研究以红松(Pinus koraiensis)为研究对象,通过测定69株胸径(DBH)0.3–100.0 cm范围内植株不同年龄枝的形态性状、化学性状和解剖性状,探讨植株大小(DBH或树高)、枝龄与环境因素(光照强度、土壤养分及土壤含水率)对枝性状的影响。结果表明:(1)DBH与树高对枝性状的影响存在差异:木质密度(WD)、木质部面积占比(RXA)、韧皮部面积占比(RPHA)及髓面积占比(RPA)对DBH更敏感,而树脂道总面积占比(RRC)和枝氮含量(WN)受树高影响更大;(2)枝龄是导致红松枝性状种内变异的最主要因素,植株大小次之,而环境因素的影响最小;(3)WD、RPHA与DBH显著正相关,RPA与DBH显著负相关,RRC、WN与树高显著正相关;除WN外,其余枝性状与枝龄均显著相关,且随着树木生长,RRC随枝龄增大而减小的速率加剧,相反,RPA随枝龄增大而减小的速率减缓。研究结果有助于了解局域尺度上枝性状种内变异的影响因素以及枝条应对环境变异的适应机制。

Seasonal changes in tannin and nitrogen contents of Casuarina equisetifolia branchlets

Seasonal dynamics of total phenolics (TP), extractable condensed tannins (ECT), protein-bound condensed tannins (PBCT), fiber-bound condensed tannins (FBCT), total condensed tannins (TCT), and protein precipitation capacity (PPC) in young, mature and senescent branchlets of Casuarina equisetifolia were studied at Chishan Forestry Center of Dongshan County, Fujian Province, China. In addition, nitrogen contents of branchlets at the different developmental stages were also determined. The contents of TP and ECT, and PPC in young branchlets were significantly higher than those in mature and senescent branchlets through the season. However, PBCT contents were significantly higher in senescent branchlets than those in young and mature branchlets; FBCT fluctuated with season. Young branchlets had the highest N content, which decreased during branch maturity and senescence. The highest contents of TP and the lowest contents of TCT and N in young and mature branchlets were observed in summer. There was a significant negative correlation between TP and N contents. In contrast, TCT contents were positively correlated to N contents. Nutrient resorption during senescence and high TCT:N ratios in senescent branchlets are the important nutrient conservation strategies for C. equisetifolia.

Leaf Longevity in a Timberline Tree Species Juniperus saltuaria in the Sergymla Mountains,Southeastern Tibet

Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain.Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs,leaf longevity is rarely studied in Cupressaceae species,which further limits our understanding of the leaf economic spectrum (LES) for these populations.Here,we investigated the leaf longevity,as well as mass-based leaf nitrogen concentration (N;),of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains,southeastern Tibet.We found that the mean leaf longevity was 4.2±1.2 years,and overall it did not differ significantly between different elevations.Along the vertical profiles of juniper canopies,the leaf longevity did not reflect a linear trend.With increasing leaf longevity,N;showed declining trends.We further analyzed the relationship between leaf longevity and the corresponding length of green twigs,and found that the length of green twigs could only explain 1%-3%of the variation in leaf longevity,indicating that the length of green twigs is a poor predictor for the variation in leaf longevity.In summary,for the J.saltuaria species in timberline or nearby subalpine forests,the effects of elevation and canopy depths on leaf longevity are minor,and the leaf trait analysis is in accordance with the prediction of LES.