Rock phosphate and vesicular-arbuscular mycorrhiza effects on growth and nutrient uptake of Faidherbia albida (Del.) seedlings in an alkaline sandy soil

Response of Faidherbia albida (Del.) to five levels of Kodjari rock phosphate (KRP) application (0, 310, 620, 1240 and 2480 ppm P, equivalent to 0, 775, 1550, 3100 and 6200 kg P/ha) and vesicular-arbuscular mycorrhizal fungi (VAMF) Glomus manihotis Howeler, Sieverding & Schenck or Glomus aggregatum Schenck & Smith emend. Koske was evaluated in an alkaline sandy soil. The F. albida seedlings grew poorly without mycorrhizal colonization and without KRP applications. For non-VAM Faidherbia, the maximum growth response and both P and N uptake in shoots was achieved with the 620 ppm P. However, even without KRP application, VAM plants achieved better results in terms of biomass. VAM plants with G. manihotis and G. aggregatum improved plant growth and increased nutrient contents at any KRP application rate. Although mycorrhizal colonization was comparable at all levels of KRP application, the impact of nutrient content of the shoot varied. Finally, VAM plants did not accumulate more biomass than non-VAM plants at 620 ppm P and above. Growth response and mycorrhizal dependency decreased as KRP applied levels increased. These results suggest that VAM Faidherbia seedlings take up more P from soil and KRP than non-VAM.     

The influence of Desert False Indigo, <Emphasis Type="Italic">Amorpha fruticosa</Emphasis>, and three arbuscular mycorrhizae fungi on the growth of <Emphasis Type="Italic">Populus ussuriensis</Emphasis> seedlings

The influence of Desert False Indigo, Amorpha fruticosa, on the growth of Populus ussuriensis seedlings inoculated with three arbuscular mycorrhizae (AM) fungi (Glomus mosseae, Glomus intraradices, Glomus sinuosa) was studied using the nylon net method. The results showed that all three AM fungi infected P. ussuriensis seedlings and G. intraradices and also G. mosseae infected A. fruticosa. The AM fungi promoted growth of P. ussuriensis and Desert False indigo seedlings. Moreover, under co-cultivation with A. fruticosa, the biomass of P. ussuriensis increased significantly. The concentration of nitrogen in P. ussuriensis grown with A. fruticosa and the concentration of soluble nitrogen in the rhizosphere were also higher than when grown alone. Hypha were found on the two plant seedlings inoculated with G. mosseae and G. intraradices, suggesting that AM fungi may transport nutrients from seedlings of A. fruticosa to the rhizosphere of P. ussuriensis seedlings, which may have promoted the growth of P. ussuriensis. The AM fungi played a critical role on the effect of A. fruticosa on growth of P. ussuriensis.     

Growth of Nursery-grown Bamboo Inoculated with Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria in two Tropical Soil Typeswith and without Fertilizer Application

A nursery experiment was conducted to assess the effect of bioinoculants (Glomus aggregatum, Bacillus polymixa, Azospirillum brasilense) on seedling growth promotion of bamboo (Dendrocalamus strictus (Roxb.) Nees.) in two soil types (alfisol, vertisol) with or without fertilizer application. Bamboo seedlings were grown in the presence or absence of bioinoculants either individually or in all combinations for 180 days in field soil under tropical nursery conditions. Shoot, rhizome and root length, dry masses, nutrient concentrations and arbuscular mycorrhizal (AM) colonized root lengths were determined at harvest. Under the experimental condition tested combined inoculation of AM fungi, PSB and A. brasilense resulted in maximum growth response both under fertilized and unfertilized conditions in both soil types. Fertilizer application enhanced the efficiencies of N, P and K uptake, whereas reduced their usage efficiencies. Though soil type did not affect microbial inoculation response, fertilizer application significantly affected plant response to microbial inoculation.     

Improvement of early growth of two tropical peat-swamp forest tree species Ploiarium alternifolium and Calophyllum hosei by two arbuscular mycorrhizal fungi under greenhouse conditions

Tropical peat-swamp forests are one of the largest near-surface reserves of terrestrial carbon. However, many peat-swamp forest tree species have resulted in the reduction due to over-exploitation, forest fires and conversion into agricultural land in Indonesia. The objective of this study was to determine the effects of two arbuscular mycorrhizal (AM) fungi, Glomus clarum and G. aggregatum, on the early growth of two slow-growing peat-swamp forest tree species, Ploiarium alternifolium and Calophyllum hosei, under greenhouse conditions. Cuttings of P. alternifolium and C. hosei were uninoculated or inoculated with G. clarum and G. aggregatum and grown under greenhouse conditions for 6 months. Percentage AM colonization, plant growth, phosphorus (P) concentration and survival rate were measured. The AM colonization of P. alternifolium and C. hosei ranged from 27 to 32% and 18 to 19%, respectively. Colonization by G. clarum and G. aggregatum increased shoot height, stem diameter, leaf number, and shoot and root dry weights. Cutting shoot P content were increased by AM fungal colonization. The survival rates of inoculated plants were higher (100%) than those of control plants (67%). The results suggest that inoculation with AM fungi improves early growth of P. alternifolium and C. hosei in a tropical peat-swamp forest and can therefore contribute to rehabilitation of peat-swamps.     

Seed source and vesicular-arbuscular mycorrhizal symbiont affects growth of Juglans nigra seedlings

Seedlings of Juglans nigra from three seed sources were grown in fumigated soil without vesicular-arbuscular mycorrhizal (VAM) fungi or inoculated with Gigaspora margarita, Glomus deserticola or Glomus etunicatum. Vesicular-arbuscular mycorrhizal development varied significantly between fungal symbionts within a black walnut source. Glomus deserticola and G. etunicatum produced the highest levels of root colonization in all sources. Significant differences in seedling shoot and root growth were attributed to root colonization by specific VAM fungi in each black walnut source. Glomus deserticola stimulated seedling leaf area and root weight 26 and 52%, respectively, in one seed source. Seedling leaf N, P and K concentrations were significantly improved by VAM in two seed sources. Juglans nigra seedlings respond favorably to VAM colonization. However, differences between seed sources suggest a strong host-symbiont interaction.     

Effect of endomycorrhizae (VAM) on bamboo seedling growth and biomass productivity

The role of vesicular-arbuscular mycorrhizae (VAM) fungi symbiosis with bamboo seedling was investigated. VAM species Glomus aggregatum, G. fasciculatum and G. mosseae were inoculated individually and in combinations with the bamboo seedlings. The percentage of infection and various growth parameters such as the number of shoots, number of rhizome, internodal distance, leaf length and breadth and total biomass production were studied in myocorrhizal and non-mycorrhizal infected plants. The above findings indicated a significant increase in the growth rate and biomass productivity.     

Selection of efficient VA mycorrhizal fungi for Casuarina equisetifolia—second screening

An investigation was carried out to screen and select efficient vesicular arbuscular mycorrhizal (VAM) fungi for inoculating the forest tree species, Casuarina equisetifolia. The seedlings were inoculated with 10 different VAM fungi, obtained from various sources. Inoculated seedlings generally had greater plant height, stem girth, biomass and P content than uninoculated plants. They also had more mycorrhizal root colonization and spore numbers in root zone soil. C. equisetifolia seedlings responded best (in biomass) to inoculation with Glomus mosseae (Nicolson and Gerdemann) Gerdemann and Trappe, closely followed by Acaulospora laevis Gerdemann and Trappe and G. fasciculatum (Thaxter Sensu Gerdemann) Gerdemann and Trappe; all the three being statistically on par with each other.     

Vesicular-arbuscular mycorrhiza effects on Gliricidia sepium and Senna siamea in a fallowed alley cropping system

Nitrogen fixing and non-N₂ fixing legumes such as Gliricidia speium and Senna siamea have been used in alley cropping systems for soil improvement and source of N for food crops. However their establishments could be limited by P and moisture deficiencies in degraded soils. Vesicular-arbuscular mycorrhizal fungi can help to overcome these deficiencies. We examined the effects of a vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus deserticola, on the performance of sole hedgerow trees of Gliricidia sepium and Senna siamea and their mixtures (interplanted) in a fallowed alley cropping experiment on a degraded Alfisol in southwestern Nigeria. Percentage root infection by VAM fungi was higher in inoculated plants than in uninoculated ones irrespective of whether they were interplanted or non-interplanted. Inoculation with G. deserticola increased dry matter accumulation and nutrient uptake (N. P, Mg and K) but there was no significant interaction between mycorrhizal inoculation and interplanting for growth and nutrient uptake except for the uptake of P, Mg and K in G. sepium. Inoculation with G. deserticola reduced leaf shedding of G. sepium by 50% but did not have the same effect for S. siamea. For both tree species inoculated plants extracted more water from 0–30 cm depth than the uninoculated ones.     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.     

Growth response of <Emphasis Type="Italic">Acacia mangium</Emphasis> Willd. seedlings to arbuscular mycorrhizal fungi and four isolates of the ectomycorrhizal fungus <Emphasis Type="Italic">Pisolithus tinctorius</Emphasis> (Pers.) Coker and Couch

Some Acacia mangium Willd. plantations in Asia grow poorly due to low soil fertility and the absence of compatible mycorrhizal fungi. This legume tree can be colonized by arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi but inoculation is not routinely practiced. This study aimed to compare the effectiveness of AM fungi and four isolates of the ECM fungus Pisolithus tinctorius (Pers.) Coker and Couch (Pt) in promoting growth of A. mangium seedlings under glasshouse conditions. AM inoculants were: Glomus etunicatum, G. fasciculatum, G. macrocarpum and Gigaspora margarita and mixed species extracted from rhizosphere soil of a Populus stand in Suwon (AMKFRI), and Carex (AMM6) and Populus (AMM7) growing in mine tailings in Korea. Pisolithus isolates were from Philippines (PtPhil) and Korea (PtKFRI, PtMKACC, PtKACC). Generally, ECM fungi promoted height and diameter growth of A. mangium more than the AM inoculants. The Korean Pisolithus increased plant dry weight by 122–145%, mixed AM inoculants by 61–97%, and Glomus and Gigaspora by 45–72% over the control. PtKACC gave the highest root colonization and promoted the highest growth and concentration of most nutrients. Mycorrhizal root colonization was positively correlated with plant dry weight, Na, Fe and Cu concentrations and N, P, K, Ca, Na, Fe and Cu contents. In conclusion, the results provide strong evidence for benefits of mycorrhizal inoculation on A. mangium seedlings under glasshouse conditions. The Korean Pisolithus isolates (particularly PtKACC), and two AM fungi (AMKFRI and AMM6) are potential mycorrhizal inoculants but their effectiveness and persistence should be determined on degraded lands in tropical countries where A. mangium is being planted for rehabilitation.     

A comparison of agrisilvicultural systems with plantation forestry in the Atlantic Lowlands of Costa Rica

Survival and growth data (ages 0–5 years) are presented for two timber species (Acacia mangium, Cordia alliodora) planted in monocultures or in association with a sequence of agricultural cropsZea mays, Zingiber officinale andEugenia stipitata (a fruit shrub) in the tropical humid Caribbean lowlands of Costa Rica. Average annual height and diameter growth rates were 3.2 m and 4.0 cm (C. alliodora), 3.5 m and 3.8 cm (A. mangium).C. alliodora associated with crops gave the greatest productivity with an average total stem volume increment of 19 m³ ha^–1 yr^–1. Root rot ofA. mangium (mainlyRosellinia sp.), leading to tree mortality, was greater in pure plots compared to associated plots.A. mangium can not be recommended for similar sites because of this problem.     

Possibility of improvement in fundamental properties of wood of acacia hybrids by artificial hybridization

Growth, specific gravity, and wood fiber length of Acacia mangium, Acacia auriculiformis, artificial acacia hybrid clones, and combinations, which were planted in a trial forest in Bavi, Vietnam, in July 2001, were examined. The radial variations from pith to bark were investigated to clarify the effect of genetic factors on these traits. Superiority of hybrids over their parents ranged from 36.3% to 41.6% for diameter, from 20.0% to 25.3% for height, from 6.9% to 20.7% for specific gravity, and from 6.1% to 12.8% for wood fiber length. The hybrid possessed heterosis in diameter, height, specific gravity, and wood fiber length regardless of whether the female parent was A. mangium or A. auriculiformis. The profiles of wood fiber length and specific gravity in the radial direction were similar for all the trees investigated. Wood fiber length was initially 0.5–0.6 mm near the pith and then increased slowly, finally reaching 1.0–1.2 mm near the bark. The specific gravity of acacia increased from 0.49–0.58 near the pith to 0.63–0.74 near the bark. From a relative distance of 30% from the pith, the specific gravity increased slightly and seemed to be stable. The relations among tree diameter, specific gravity, and wood fiber length were fair and could be represented by positive linear regression formulas. Hybrids for which A. auriculiformis was the female parent and A. mangium was the male parent had a faster growth rate and longer wood fibers than the inverse hybrids. Part of this report was presented at the 6th Pacific Regional Wood Anatomy Conference, Kyoto, Japan, December 2005     

模拟外源性氮磷对马占相思凋落叶分解及土壤生化特性的影响

[目的]研究外源性氮和磷对马占相思凋落叶的分解速率、分解过程中N、P、K含量和土壤生化特性的影响,以便为森林土壤养分管理提供参考。[方法]以广东省云勇林场马占相思林下凋落叶为试验材料,采用尼龙网袋分解法,设置对照(CK)、施N(10 g·m~(-2))、施P(5 g·m~(-2))、施N+P(N 10 g·m~(-2)+P 5 g·m~(-2))4种处理,每隔3个月取样1次,并测定凋落叶残留量和N、P、K含量。[结果]表明:施N、P和N+P处理对马占相思凋落叶的分解均为促进作用。各处理马占相思凋落叶的N含量在分解过程中大致保持稳定,施P和N+P处理的凋落叶P含量在分解过程中总体呈波动性上升,而各处理的凋落叶K含量变化规律不明显。施N、P和N+P处理提高了马占相思林土壤的有机质和全N含量,促进脲酶、磷酸酶及过氧化氢酶的活性。[结论]施N、P和N+P处理促进了马占相思凋落叶的分解,有利于马占相思林的养分循环。     

海南尖峰岭两类人工林中天然更新群落特征研究

25-years-old Cunninghamia lanceolata forests and 18-years-old Acacia mangium forests in Jianfengling of Hainan Province were surveyed to assess the structures and species diversity of naturally-regenerated plants. The results showed that there were 131 species in C. lanceolata forests, attributed to 100 genera and 51 families. The dominant species were Gironniera subaequalis, Schima superba, Pertusadina metcalfii and Polyspora hainanensis. There were 62 species in A. mangium forests, attributed to 59 genera and 33 families. The dominant species were Acronychia pedunculata, Tetradium glabrifolium, Machilus chinensis, Gironniera subaequalis and Toxicodendron succedaneum. The species richness, Simpson index and Shannon-Wiener index for naturally-regenerated plants in C. lanceolata forests were 76.67±11.02, 0.94±0.04 and 3.50±0.49,while those in A. mangium forests were 39.00±8.54, 0.91±0.04 and 3.05±0.27. The Sørensen species similarity for naturally-regenerated plants of the two forests was 0.50, with a increasing age structure. The mean density, height and dbh for adult trees of naturally-regenerated components of C. lanceolata forests were significantly lower than A. mangium forests; while the mean density and height of small tress of naturally-regenerated components of C. lanceolata forests were significantly higher than A. mangium forests. The study indicated that the naturally-regenerated plant species increased, and the forest structures became complex with the regeneration of both C. lanceolata and A. mangium forests. These two pure plantations will become old-growth natural forests with the forest succession.     

Growth and nutrient concentration of two native forage legumes inoculated with Rhizobium and Mycorrhiza in Missouri, USA

The Center for Agroforestry at the University of Missouri has tested numerous native legumes for potential use in agroforestry and selected Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson and Fern.) and panicled tick clover (Desmodium paniculatum (L.) DC.) for further testing. Our objective was to document the effect of arbuscular mycorrhizae (AM) (Glomus spp.) and Rhizobium on growth and nutrient concentration of these legumes. Seeds were planted in a greenhouse and inoculated with one of two species of AM and/or one of two strains of Rhizobium. Plants were harvested after 80 d and data taken on leaf and stem dry weight, root fresh weight, stem height, nodulation, AM colonization, and N, P, K, Ca, and Mg concentration. Inoculation with Rhizobium did not affect plant growth in Illinois bundleflower, but colonization by Glomus intraradices increased all plant growth variables except stem height. Nutrient concentration was unaffected by the presence of either endophyte. In contrast, inoculation of panicled tick clover with Rhizobium str. 41Z10 increased leaf dry weight (32%) compared to the control and root fresh weight (41%) compared to str. 32Z3, and colonization by G. intraradices increased leaf dry weight (35%) and stem height (26%). Both species of AM increased P and K concentration (41% and 55%, respectively) in panicled tick clover. Our results suggest that the growth of these legumes can be improved by the use of proper AM species and/or Rhizobium strains. However, additional research to identify the best Rhizobium and AM inoculates for these plant species is important in developing strategies for their use in agroforestry. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth and yield modelling of <Emphasis Type="Italic">Acacia mangium</Emphasis> in Colombia

To study the growth and yield of Acacia mangium in the Caribbean region of Colombia, allometric equations of total volume and aboveground plus coarse roots biomass were fitted as a function of the tree’s diameter at breast height (dbh). The von Bertalanffy’s growth model and 59, 0.1 ha plots (0.55–9.55 years old) were used to develop site index (SI) curves at 6 years base age. Then, using the state-space approach, stand growth and yield models were developed for basal area, volume and biomass. The results show that A. mangium is a very promising species for timber production, atmospheric carbon removal and soil restoration because it grows very fast even in mining degraded soils. On average sites it reaches 15 m in height in 3 years. However, early and reiterated thinning coupled with initial mortality by cattle invasion of the very young understocked plantations are producing relatively low yields.     

Species and site selection for timber production on farm boundaries in the humid Atlantic Lowlands of Costa Rica and Panama

In 1987–89 the CATIE-GTZ Agroforestry Project set up experiments with five timber tree species planted in single lines on twelve farm boundaries in cooperation with local farmers. When the trees were five years old, their height, diameter and total stem volume were: Acacia mangium 17 m, 19 cm and 67 m³ km^–1, Cordia alliodora 14 m, 20 cm and 46 m³ km^–1, Eucalyptus deglupta 22 m, 24 cm and 85 m³ km^–1, Tectona grandis 17 m, 20 m and 64 m³ km^–1, Terminalia ivorensis 18 m, 23 cm and 104 m³ km^–1. Considering these excellent growth rates, planting of Cordia alliodora, Eucalyptus deglupta and Tectona grandis in lines on farm boundaries should be promoted. T. ivorensis and A. mangium are not recommendable for sites with impeded drainage because of mortality caused by root rot, mostly due to Rosellinia sp.     

Function and value of water conservation in different age classes of Acacia mangium plantations

For this paper, we studied the water-holding capacity of canopy, vegetation layer under canopy and litter layer, the water-holding capacity and permeability of soil as well as their changes with growth of stands in Acacia mangium plantations of three different age classes (four-, seven-and 11-year-old). Results show that total water-holding above ground in the order of 11-year stand age (52.86 t/hm²)>seven-year stand age (41.90 t/hm²)>seven-year stand age (25.78 t/hm²), the increment tendency increased with stand age. Similar sequence also obtained on the water-holding capacity and permeation capacity of soil (0–40 cm). The total water-storage capacity both above ground and soil in four-year-old, seven-year-old and 11-year-old of A. mangium plantations were 2,023.0, 2,158.4 and 2,260.4 t/hm², respectively, and the all value of water conservation were 1,372.70, 1,474.42 and 1,549.91 yuan (RMB)/hm², respectively. Therefore, A. mangium plantation had a good ability to modify soil structure and good water conservation function. __________ Translated from Journal of Soil and Water Conservation, 2006, 20(5): 5–8, 27 [译自: 水土保持学报]     

Polyphenols in Acacia mangium and Acacia auriculiformis heartwood with reference to heart rot susceptibility

The heartwood of Acacia mangium is vulnerable to heart rot and this is the first study to investigate the role of heartwood extractives in its susceptibility. Acacia auriculiformis was compared with A. mangium because it is rarely associated with heart rot. The heartwood extracts of both species were dominated by three flavonoids (2,3-trans-3,4′,7,8-tetrahydroxyflavanone, teracacidin, and 4′,7,8,-trihydroxyflavanone), which were purified and identified by nuclear magnetic resonance spectroscopy. The latter compound has not been previously reported in A. mangium and evidence for melacacidin is also newly reported. The mass spectrometric (MS) behavior of these compounds is given, for example teracacidin does not form molecular ions by either electrospray ionization or atmospheric-pressure chemical ionization. The nature of Acacia tannins was compared to quebracho tannin (composed of profisetinidins) using oxidative cleavage to enable MS detection but a negative reaction was obtained for both, which suggests the Acacia tannins may also be of the 5-deoxy proanthocyanidin type. The concentration of flavanones was less when A. mangium heartwood was decayed but the amount of proanthocyanidins was only slightly reduced and therefore these compounds may be more resistant to degradation by heart rot fungi. We found that the total phenol content of A. auriculiformis was about fivefold that of A. mangium, and, while preliminary, this provides evidence for a role played by phenolic extractives in heart rot resistance of these Acacia species.     

Effect of Arbuscular Mycorrhiza on the Drought Tolerance of Poncirus trifoliata Seedlings

The effects of Glomus mosseae colonization on the plant growth and drought tolerance of 1-year-old trifoliate Poncirus trifoliata seedlings in potted culture were studied in natural water stress and rewatering conditions. Results showed that arbuscular mycorrhizal (AM) inoculation significantly improved the height, stem diameter, and fresh weight of P. trifoliata seedlings before natural water stress. By the end of the experiment, the survival percentage of AM-transplanted seedlings was 8% higher than those of non-AM ones. During water stress and rewatering, AM significantly increased the contents of soluble sugars and proteins in leaves, and enhanced the activities of superoxide dismutase (SOD), guaiacol peroxidase (G-POD), and catalase (CAT) in either seedling leaves or roots, which indicated that AM colonization could improve the osmotic adjustment response of P. trifoliata, enhance its defense system, and alleviate oxidative damages to membrane lipids and proteins. These results demonstrated that the drought tolerance of P. trifoliata seedlings was increased by inoculation with AM fungi. The functional mechanism underlying the observation that mycorrhizas increased the host’s drought tolerance was closely related to enzymatic and nonenzymatic antioxidant defense systems such as SOD, G-POD, CAT, and soluble protein. Translated from Chinese Journal of Applied Ecology, 2005, 16(3) (in Chinese)