以7个马尾松(Pinus massoniana)一代种子园自由授粉家系为材料, 设置同质低磷(P)胁迫和异质低P胁迫模拟的盆栽试验, 系统研究马尾松家系对不同类型低P胁迫的适应机制和P效率变异规律。结果表明, 参试马尾松家系的苗高、地径和生物量等P效率指标均表现出显著的家系变异, 主要P效率指标的家系遗传力均较高, 干物质积累量的广义遗传力大于0.80, 揭示了马尾松P营养效率的较大遗传改良潜力。马尾松对不同类型低P胁迫的适应机制有所差异。在同质低P胁迫下, ‘3201’、‘1217’等高P效率家系的根系主要参数均高于低P效率家系, 表明整体根系参数的适应性变化是P效率和生物量形成的决定因素。在异质低P胁迫下, 高P效率马尾松家系在表层富P介质的根系分布量、分布比例均显著增加, 表层根系参数与马尾松家系P效率呈显著正相关, 揭示根系空间构型的适应性变化是决定马尾松高P效率的重要生物学基础。表层根系生物量、表层根相对比例的家系遗传力达0.88和0.72, 证实了以马尾松根构型的适应变化为突破口, 选育具有理想根构型和较高P效率的马尾松家系。

<p><em>Aims</em> Our aim was to investigate the genotypic variations among semi-sib families of <em>Pinus massoniana</em> for adaptive changes in root morphology and architecture in response to different types of low soil phosphorus (P) availability and their relationships to plant growth and P efficiency.</br><em>Methods</em> Pot experiments were conducted during the 2010 growing season in a nursery located in Chun&rsquo;an County of Zhejiang Province, China. Seven semi-sib families of <em>P. massoniana</em> contrasting in root architecture and P efficiency were compared for their root morphological and architectural traits and their relationships to plant growth and P efficiency under both heterogeneous and homogeneous low P conditions.</br><em>Important findings</em> Large genotypic variations were observed under different types of low-P conditions. The adaptive mechanism for P deficiency was different under heterogeneous and homogeneous low-P conditions. Under homogeneous low-P conditions, adaptive responses of root growth parameters were present in genotypes with high-P efficiency such as &lsquo;3201&rsquo; and &lsquo;1217&rsquo;, while it was not observed in genotypes with low-P efficiency. Root architecture was not closely related to plant P efficiency under homogeneous low-P conditions. Under heterogeneous low-P conditions, root architecture was found to closely related to P efficiency. Genotypes with shallow root architecture had optimal root parameters including root length, surface area and biomass in the top layer of soil, thus having the greater ability for P absorption and having higher P efficiency and biomass. The heritability for the root biomass and the proportion of root in the top soil layer was 0.88 and 0.72, respectively. A significant interactive effect between patterns of low-P conditions and P efficiency was observed. Given that <em>P. massoniana</em> has great genetic potential for adaptation to low-P soils, the selection of high-P efficiency genotypes with optimal root architecture may significantly increase wood production of <em>P. massoniana</em> under low-<em>P conditions</em>.</p>

辽东栎（Quercus liaotungensis）是中国暖温带落叶阔叶林的主要优势树种之一。铆钉菇（Gomphidius viscidus）和臭红菇（Russula foetens）是在自然环境中与其共生形成外生菌根的真菌。在前期工作证明铆钉菇和臭红菇接种对辽东栎幼苗生长有明显促进作用并以两菌种混合接种效果较好的基础上，探讨了不同的接种量和两个菌种不同比例的混合接种对辽东栎幼苗生长和氮、磷养分的影响。对应于试验的12、18、24 g&middot;pot-1 3个接种量处理，随着接种量的增加，辽东栎幼苗的菌根侵染率增加，铆钉菇菌根的比例增加，而臭红菇菌根的比例减少。辽东栎幼苗的生物量、株高、净光合速率和全株的全氮、全磷含量，均以18 g&middot;pot-1接种量的最高。当接种物中铆钉菇∶臭红菇的比例分别为2∶1、1∶1、1∶2时，辽东栎幼苗的菌根侵染率分别为96.54%、91.02%、92.13%，但彼此间差异不显著。随着接种物中铆钉菇比例的减少，铆钉菇菌根所占比例由42.49%降为23.33%，而臭红菇菌根的比例由57.51%增加为76.67%。辽东栎幼苗的生物量和净光合速率均是以接种比例为1∶1的最高。接种比例为1∶1的辽东栎幼苗的全氮含量也是最高的，并且与另两种接种比例处理的差异显著，而对于全株的全磷含量，则是随着接种物中臭红菇的比例增加而增加。

<p>Quercus liaotungensis, a special Quercus species of China, is one of the dominant species in the warm temperate deciduous broad-leaved forests, China. Gomphidius viscidus and Russula foetens are two species of ectomycorrhizal fungi being symbiosis and formation of ectomycorrhizae with Q. liaotungensis in the natural circumstance. The positive effect of the inoculation with G. viscidus and R. foetens on Q. liaotungensis seedling growth, and the improvement induced by co-inoculation with a mixed inoculum of G. viscidus and R. foetens have been reported in our early work. In the present paper, a controlled experiment was conducted in pots to investigate the effects of different inoculation amounts and different inoculation ratios of G. viscidus and R. foetens. Q. liaotungensis seeds were collected in autumn of 2001 from the natural forest of Mt. Donglingshan in the Beijing area. Before germination, seeds were rinsed in running tap water overnight, surface disinfected by shaking for 60 min in 0.5% KMnO4 and washed in four changes of sterile distilled water. Seeds were germinated in sterile sand, and seedlings were transplanted to pots (diameter 20 cm, depth 20 cm) with a sterile mixture of soil and sand in a greenhouse. The sterile mixture had a pH of 6.9, an organic matter content of 3.76%, and total N, P, K levels of 0.30%, 0.12% and 2.61%, respectively. On June 2, 2002, every 15 pots of Q. liaotungensis seedlings were randomly grouped for inoculation treatment. Three levels of inoculation amount of 12, 18 and 24 g&middot;pot-1 were created at the ratio of 1∶1 of G. viscidus∶R. foetens, and three ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus∶R. foetens were inoculated at the inoculum amount of 18 g&middot;pot-1. After 3 months of inoculation, the mycorrhizal infection rate and the percentages of G. viscidus and R. foetens mycorrhizae were observed. The height, dry weight, nitrogen and phosphorus contents of root, stem and leaf, net photosynthesis rate of the mycorrhizal seedlings and non-mycorrhizal seedlings were measured, and biomass, nitrogen and phosphorus contents of the whole plant, root/shoot ratio and leaf water content were calculated.The infection rate of mycorrhizae of Q. liaotungensis seedlings and the percentage of G. viscidus mycorrhizae increased but the percentage of R. foetens mycorrhizae decreased when the inoculation amount was higher. The maximum biomass, height, net photosynthesis rate and total nitrogen and phosphorus contents of whole plant of Q. liaotungensis seedlings all showed in plants with inoculation amount of 18 g&middot;pot-1. As to inoculation ratio, with the inoculum ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus and R. foetens, the infection rates of total ectomycorrhizae were 96.54%, 91.02% and 92.13% respectively, and no significantly difference among them. As the proportion of G. viscidus in the inoculum decreased, the percentage of G. viscidus mycorrhizae decreased from 42.49% to 23.33%, and that of R. foetens mycorrhizae rose from 57.51% to 76.67%. With an inoculation amount of 18 g&middot;pot-1 at a ratio of 1∶1 G. viscidus∶R. foetens, the seedlings of Q. liaotungensis have maximal biomass, net photosynthesis rate, and total nitrogen content of the whole plant which was significantly higher than seedlings under other inoculation ratio conditions. Total phosphorus content of the whole plant of Q. liaotungensis was enhanced by the increasing ratio of R. foetens.</p>

Nitrogen (N) uptake and utilization in seedlings of six full-sib families of coastal Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) known to differ in growth rate were assessed at the whole plant and root levels. Seedlings were grown in soil or aeroponically with high and low nutrient availability. Consistent family differences in growth rate and N utilization index were observed in both soil and aeroponic culture, and high-ranking families by these measures also had greater net N uptake in soil culture. Two of the three families found to be fast-growing in long-term field trials exhibited faster growth, higher N utilization indices and greater net N uptake at the seedling stage. Mean family net influx of ammonium (NH4+) and efflux of nitrate (NO3-) in the high- and low-nutrient treatments were significantly correlated with measures of mean family biomass. The high-nutrient availability treatment increased mean net fluxes of NH4+ and NO3- in roots. These results indicate that efficiency of nutrient uptake and utilization contribute to higher growth rates of trees. Nutrient-related traits should be considered in tree breeding programs, as the indications are that assessments may be made at an early stage.

为探究氮沉降和接种菌根真菌对长白落叶松苗木根系构型和根际土壤酶活性的影响，以1年生长白落叶松（Larix olgensis）的盆栽菌根苗（简称+M，混合接种8种外生菌根真菌）和非菌根苗（简称-M，未接种处理） 为研究对象，设置4个氮沉降处理（不施氮（0N，0 kg·N·hm^-1·yr^-1）、低氮（LN，15 kg·N·hm^-1·yr^-1）、中氮（MN， 30 kg·N·hm^-1·a^-1）和高氮（HN，60 kg·N·hm^-1·a^-1）），测定直径0~0.5 mm根系的总根长、总表面积、总体积和根尖数等根系形态指标，对比分析氮沉降和接种菌根真菌处理对苗木根际土壤酶（β-1，4葡萄糖苷酶（BG）、亮氨酸氨基肽酶（LAP）、β-1，4-N-乙酰-氨基葡糖氨糖苷酶（NAG）、酸性磷酸酶（ACP）和碱性磷酸酶（ALP））活性的影响。结果表明：①长白落叶松苗木直径0~0.5 mm根系的总根长、总表面积、总体积和根尖数均随氮浓度的递增呈下降的趋势；在0N、LN和MN处理下，-M处理的根系形态指标均高于+M处理。②随氮浓度增加，+M和-M处理苗木根际土壤中BG、LAP、ACP和ALP活性均呈先增加后下降的趋势，而NAG活性呈下降的趋势。③+M和-M处理下，长白落叶松直径0~0.5 mm根系的形态指标与根际土壤BG活性均呈显著负相关关系（P&lt;0.05）；除根尖数外，其它根系形态指标与NAG活性相关性均为正相关（P&lt;0.05）。综上所述，苗木菌根化处理削弱了氮沉降对落叶松苗木根系构型的影响；而低氮处理下，+M处理对苗木根际土壤酶的活化程度高于-M处理。

• Biologically essential elements--especially nitrogen (N) and phosphorus (P)--constrain plant growth and microbial functioning; however, human activities are drastically altering the magnitude and pattern of such nutrient limitations on land. Here we examine interactions between N and P cycles of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial biomes. • We synthesized results from 34 separate studies and used meta-analysis to evaluate phosphatase activity with N, P, or N×P fertilization. • Our results show that N fertilization enhances phosphatase activity, from the tropics to the extra-tropics, both on plant roots and in bulk soils. By contrast, P fertilization strongly suppresses rates of phosphatase activity. • These results imply that phosphatase enzymes are strongly responsive to changes in local nutrient cycle conditions. We also show that plant phosphatases respond more strongly to fertilization than soil phosphatases. The tight coupling between N and P provides a mechanism for recent observations of N and P co-limitation on land. Moreover, our results suggest that terrestrial plants and microbes can allocate excess N to phosphatase enzymes, thus delaying the onset of single P limitation to plant productivity as can occur via human modifications to the global N cycle.© 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.