Influence of soil fertility on the rhizobial competitiveness for nodulation of <Emphasis Type="Italic">Acacia senegal</Emphasis> and <Emphasis Type="Italic">Acacia nilotica</Emphasis> provenances in nursery and field conditions

Within the framework of our study, we assessed the nodule occupancy of a mixture of various strains of rhizobia to inoculate several provenances of Acacia senegal and Acacia nilotica. The first part of the experiment was carried out under greenhouse conditions where the plants were cultivated in polyvinyl chloride tubes containing an unsterilized Sangalkam soil low in organic matter and nitrogen. The results showed that 4 and 8 months after sowing, rhizobial strains CIRADF 306 and CIRADF 300 were mainly present in nodules of A. nilotica and A. senegal, respectively. After transferring the seedlings to the more fertile soil in Bel Air field station, the molecular analysis of the nodules showed that strain CIRADF 306 was absent from the nodules of A. nilotica, whereas strain CIRADF 305 which occurred only at low nodule occupancy in the nursery, predominated in the field conditions. On the other hand, strain CIRADF 300 occurred in the majority of the nodules from the various provenances of A. senegal. These results demonstrated actual interaction between inoculated rhizobial strains, soil type and host plant genotype in terms of competitiveness, nodulation and symbiotic nitrogen fixation.     

Nutritive value and voluntary feed intake by goats of three browse fodder species in the Sahelian zone of West Africa

Browsing ruminants have access to different biomass, depending on how high they can reach. Foliage consisting of leaves and green pods from Acacia senegal, Pterocarpus lucens and Guiera senegalensis, was collected according to height above ground accessible to either sheep (0.90 m), goats (1.65 m) or cattle (1.50 m). There was a significant variation in the chemical composition of the biomass between species. The crude protein (CP) content was 114, 157 and 217 g/kg dry matter (DM) and the neutral detergent fiber (aNDF) content 604, 534 and 412 g/kg DM for G. senegalensis, P. lucens and A. senegal, respectively. There was no significant variation in chemical composition according to the height accessible by cattle, sheep or goats. The voluntary intake was studied using eight goats per diet. The six diets consisted of the three browse leaves and two pods (A. senegal and P. lucens) and a control. The leaves were fed combined with hay of Schoenefeldia gracilis (maximum 30%) and the control was pure hay. Apparent digestibilities of the same diets, with the exception of G. senegalensis, were measured using five goats per diet. All browse fodders used in the feeding and digestibility trials were high in CP (105–170 g/kg DM) and lignin (164–234 g/kg DM except A. senegal leaves) and low in fiber (322–590 g/kg DM of NDF) compared to the hay (31 g/kg DM of CP and 755 g/kg DM of NDF). The highest intake was of the P. lucens diet (864 g) and the lowest of the G. senegalensis diet (397 g). The intake of pods from A. senegal was higher (1033 g) than from P. lucens pods (691 g). The apparent digestibility of OM and CP in the browse leaves was 0.63 and 0.57 and 0.63 and 0.64 for A. senegal and P. lucens, respectively, higher than for the hay, which showed higher digestibility of NDF. A. senegal pods had higher digestibility for all nutrients than P. lucens pods. Based on the high CP content and the intake and digestibility characteristics, P. lucens leaves and A. senegal leaves and pods can be recommended as protein supplements to low quality diets.     

The efficiency and competitiveness of three <Emphasis Type="Italic">Mesorhizobium</Emphasis> sp. strains nodulating <Emphasis Type="Italic">Acacia senegal</Emphasis> (L.) Willd. under water deficiency conditions in the greenhouse

The combined effects of drought and salinity were investigated on the growth, efficiency and competitiveness of three Mesorhizobium sp. strains (ORS 3416, ORS 3428 and ORS 3437) isolated from Acacia senegal (L.) Willd. Sixteen combinations of polyethylene glycol (PEG) 6000 (0, 6, 12, 20%, w/v) and NaCl (0.005, 0.5, 1, 1.5%, w/v) were used to study rhizobial strains growth in screw-capped tubes containing yeast extract mannitol liquid medium. Whatever the combination, the strains grew. However, high concentrations of PEG 6000 and NaCl were depressed on rhizobial growth but strain ORS 3428 was the most tolerant. The effect of rhizobial inoculation on growth of A. senegal plants was also examined under non-limited (100% of water holding capacity, WHC) and water-limited conditions (50% WHC) in the greenhouse for 4 months on non-sterile sandy soil. A significant decrease in the nodulation rate, nodule dry weight, plant height and shoot dry weight was observed under water-limited conditions. Nevertheless, inoculation with the three selected Mesorhizobium strains significantly improved nodulation and A. senegal plant growth under water-limited conditions. Whatever the irrigation condition, strains ORS 3428 and ORS 3437 were more competitive than ORS 3416. These rhizobial strains may prove valuable for inoculation of Acacia senegal plants grown for transplantation to dry saline habitats.     

Rhizobium nodulation inProsopis juliflora seedlings at different irrigation levels in eastern Kenya

The field phase of the present study was carried out at Bura, eastern Kenya. The introduced, drought resistantProsopis juliflora seedlings were watered at four different irrigation levels. 43 sample trees with 1772 root nodules were dug up and investigated. Several trees lacked viable root nodules especially in nonirrigated plots. Regression analysis indicated significant negative correlation between the mortality of the root nodules and the level of irrigation. Rhizobium strains, which were isolated from the sample trees, were capable of nodulating indigenousAcacia senegal.     

Nitrogen fixation in Faidherbia albida,Acacia raddiana,Acacia senegal and Acacia seyal estimated using the 15N isotope dilution technique

A pot experiment was conducted in a greenhouse using the ¹⁵N isotope dilution method and two reference plants, Parkia biglobosa and Tamarindus indica to estimate nitrogen fixed in four Acacia species: A raddiana, A. senegal, A. seyal and Faidherbia albida (synonym Acacia albida). For the reference plants, the ¹⁵N enrichments in leaves, stems and roots were similar. With the fixing plants, leaves and stems had similar ¹⁵N enrichments; they were higher than the ¹⁵N enrichment of roots. The amounts of nitrogen fixed at 5 months after planting were similar using either reference plant. Estimates of the percentage of N derived from fixation (%Ndfa) for the above ground parts, in contrast to %Ndfa in roots, were similar to those for the whole plant. However, none of the individual plant parts estimated accurately total N fixed in the whole plant, and excluding the roots resulted in at least 30% underestimation of the amounts of N fixed. Between species, differences in N₂ fixation were observed, both for %Ndfa and total N fixed. For %Ndfa, the best were A. seyal (average, 63%) and A. raddiana (average, 62%), being at least twice the %Ndfa in A. senegal and F. albida. Because of its very high N content, A. seyal was clearly the best in total N fixed, fixing 1.62 g N plant^–1 compared to an average of 0.48 g N plant^–1 for the other Acacia species. Our results show the wide variability existing between Acacia species in terms of both %Ndfa and total N fixed: A. seyal was classified as having a high N₂ fixing potential (NFP) while the other Acacia species had a low NFP.     

Selection of Bradyrhizobium strains and provenances of Acacia mangium and Faidherbia albida: Relationship with their tolerance to acidity and aluminium

This work was designed to determine the role of the acidity and aluminium stress in the selection of partners in the Acacia symbioses with relevance to the persistence of the microsymbiont Bradyrhizobium in the soil and the growth and nodulation of the host plant respectively. Fifteen strains of Bradyrhizobium from Acacia mangium and Faidherbia albida formed a very homogenous acid tolerant group as indicated by their ability to grow better in a medium at pH 4.5 than in a medium at pH 6.8. By contrast, a growth experiment using an acid liquid media (pH 4.5), containing different concentrations of aluminium successfully identified strains sensitive to aluminium toxicity and those able to grow even in the presence of 100 M AlCl₃.Our results suggest that high amounts of aluminium in the soil rather than acidity (pH 4.5) were a major soil factor for selection of Bradyrhizobium strains capable of establishing a permanently high population under natural conditions.Unlike the behaviour of the microsymbiont, growth and nodulation of Acacia mangium and Faidherbia albida were not affected by aluminium, even at 100 M, but they might be significantly affected by medium acidity (pH 4.5) depending on plant provenances. It is therefore suggested that ability of the host plant to tolerate acidity stress should be taken into account first when screening effective Acacia-Bradyrhizobium combinations for use in afforestation trials.     

Successional patterns of woody plants in catchment areas in a semi-arid region

Patterns of woody plants dispersal in a semi-arid nature reserve situated in Eastern Transvaal, South Africa, revealed that trees have spread from core areas and converted previously open grasslands to densely vegetated woodlands. These patterns were found in catchment areas of the gently undulating terrain which characterizes the region.Two plant communities dominated by Acacia senegal-Acacia tortilis and Euclea divinorum-Acacia nilotica were distinguished. Analysis of nearest-neighbour distances, dispersal patterns of seedlings and mature woody plants identified successional processes. These were manifested through intra and interspecific competition among the dominant tree species. Within each plant community, a transition of relative abundance was occurring namely, A. senegal became dominant in areas previously dominated by A. tortilis while E. divinorum was replacing previous A. nilotica dominance.Comparative assessment of the two plant communities was facilitated by the summary of competition and seedling dispersal indices in a multivariate analysis. Results indicated that tree species had characteristic dispersal strategies. Identification the patterns of woody plants establishment could advance the evaluation of successional dynamics and management of savannas in areas prone to bush encroachment.     

Symbiotic nitrogen fixation in eight Acacia senegal provenances in dryland clays of the Blue Nile Sudan estimated by the 15N natural abundance method

The symbiotic biological N₂fixation by Acacia senegal was estimated using the ¹⁵N natural abundance (δ ¹⁵N) procedure on eight provenances collected from different environments and soil types grown in a clay soil in the Blue Nile region, Sudan. Balanites aegyptiaca (a non-legume) was used as a non-N₂-fixing reference plant to allow ¹⁵N-based estimates of the proportion of the Acacia N derived from atmospheric N₂ (N_dfa) to be calculated. Results show variation in leaf δ ¹⁵N between A. senegal and the reference plant and among years. The relative δ ¹⁵N values (‰) were higher in B. aegyptiaca than in the N₂-fixing acacia provenances. Provenances originally collected from clay soils fixed little N in the first year, but the amount fixed increased as the trees aged. All provenances showed a decrease in δ ¹⁵N with age. The N_dfa varied between 24% (Mazmoom provenance) and 61% (Rahad provenance) 4 years after planting. There was no significant difference in δ ¹⁵N between provenance groups based on soil type or rainfall at original growing site. The amount of N_dfa increased significantly with age in all provenances. The above-ground contribution of fixed N to foliage growth in a 4-year-old A. senegal was highest in the Rahad sand–soil provenance (46.7 kg N ha⁻¹) and lowest in the Mazmoom clay-soil provenance (28.7 kg N ha⁻¹). Our study represents the first use of the δ ¹⁵N method for estimating the N input by A. senegal to the clay plain soils of the gum belt in the Sudan.     

Starter culture of <Emphasis Type="Italic">Pseudomonas veronii</Emphasis> strain B for aerobic granulation

Aggregation of bacterial cells is used in formation of microbial granules. Aerobically grown microbial granules can be used as the bio-agents in the treatment of wastewater. However, there are problems with start up of microbial granulation and biosafety of this process. Aim of this research was selection and testing of safe microbial strain with high cell aggregation ability to shorten period of microbial granules formation. Five bacterial strains with cell aggregation index higher than 50% have been isolated from the granules. Strain of Pseudomonas veronii species was considered as most probably safe starter culture for granulation because other strains belonged to the species known as human pathogens. The microbial granules were formed after 3 days of cultivation in case when P. veronii strain B was applied to start-up aerobic granulation process using model wastewater. The granules were produced from activated sludge after 9 days of cultivation. Microbial aggregates produced from starter culture of P. veronii strain B were more compact (sludge volume index was 70 ml/g) than those produced from activated sludge (sludge volume index was 106 ml/g). It is a first proof that application of selected safe starter pure culture with high cell aggregation ability can accelerate and enhance formation of microbial granules.     

Speed of nodulation and competitive ability among strains of Rhizobium leguminosarum bv phaseoli

This study examines the speed of nodulation of 20 strains of Rhizobium leguminosarum bv phaseoli, and relates this trait to the competitive performance of these strains with Phaseolus vulgaris L. At 25/20°C day/night temperature, and with 10⁷ cells applied per growth pouch, there was a strong positive correlation between the speed of nodulation and the competitiveness of strains with the nod ⁺ fix^– reference strain UMR 1116. Strains UMR 1084, 1125, 1165, 1173 and 1384 combined good competitive performance with extensive nodulation in the uppermost root regions. When inoculant levels in the RTM studies were reduced to 10³ cells per pouch no correlation between the apparent competitiveness of strains and their speed in nodulation was evident, presumably because cells had to undergo multiplication before infection. Nodulation was also delayed when growth temperatures were raised to 31/26°C, but a correlation was still evident between competitive performance and nodulation in the region 0.1 to 5.0 mm below the RTM at the time of inoculation. From these results speed of nodulation can be used to estimate the competitive potential of Rhizobium strains, but only under carefully regulated conditions. The effects of inoculation level and temperature on the relationship between speed of nodulation and strain competitiveness could explain the inconsistent results obtained in earlier studies on this topic.Journal paper No. 16962, Agricultural Experiment Station, University of Minnesota, St. Paul, MN 55108, USA     

Host specificity of Rhizobium strains isolated from nitrogen-fixing trees and nitrogenase activities of strain GRH2 in symbiosis with Prosopis chilensis

Host plant specificity was examined in symbiosis between Rhizobium strains isolated from legume-tree root nodules and herbaceous or woody legumes from which they were isolated. Strain GRH2 isolated from Acacia cyanophylla formed effective nodules on Acacia, Prosopis and Medicago sativa as well. Nitrogenase activity, measured as acetylene reduction, of strain GRH2 in symbiosis with Prosopis chilensis was the highest (P 0.05) among the tropical legumes studied and was similar to those found for other associations involving herbaceous legumes. Relative efficiency of nitrogenase varied from 0.3 to near 1 during the light time of the photoperiod. However no hydrogen uptake activity was detected by the amperometric method used. Rhizobium strains GRH3, GRH5 and GRH9 isolated from A. melanoxylon, P. chilensis and Sophora microphylla, respectively, also showed a very low host-range specificity. All isolates were infective and effective on at least one of the herbaceous legumes tested. These data demonstrate the lack of specificity of Rhizobium strains isolated from nitrogen-fixing tree root nodules and that these strains can form effective nodules on herbaceous legumes.     

Discrete differences between strains of different Rhizobium spp. for competitive nodule occupancy on beans

Rhizobium etli strain TAL182 and R. leguminosarum bv phaseoli strain 8002, both of which produce melanin pigment, were tested for their nodulation competitiveness on beans by paired inoculation with two strains which do not produce melanin: R. tropici strain CIAT899 and Rhizobium sp. strain TAL1145. An assay was developed to distinguish nodules formed by the melanin-producing and non-producing strains. Strain TAL182 had discrete competitive superiority over CIAT899 and TAL1145 for nodulation of beans. Nodulation competitiveness was not correlated with the ability to produce melanin pigment or the host range of the Rhizobium strains tested.The authors are with the Department of Plant Molecular Physiology, University of Hawaii, 3050 Maile Way, Gillmore 402, Honolulu, HI 96822, USA     

Survival ofFrankia strains introduced into soil

Factors affecting the establishment of Alnus/Frankia symbioses were studied partly by following the survival ofFrankia strains exposed to different soil conditions, and partly by investigating the effect of pH on nodulation. TwoFrankia strains were used, both of the Sp⁻ type (sporangia not formed in nodules). One of the strains sporulated heavily, while the other formed mainly hyphae. The strains originated fromAlnus incana root nodules growing in soils of pH 3.5 and 5.0. The optimum pH for their growth in pure culture was found to be 6.7 and 6.2, respectively. The strains were introduced into twoFrankia-free soils, peat and fine sand. Their survival, measured as the persistance of nodulation capacity using the plant infection technique, was followed for 14 months. The survival curves of the strains were similar despite the morphological differences between the strains in pure culture. The nodulation capacities declined over time both at 14 and 22°C. Survival was better in soils limed to a pH above 6 than in soils at their original pH (peat 2.9, fine sand 4.2). The effect of pH on nodule formation in Alnus seedlings by theFrankia strains was studied in liquid culture. The number of nodules increased linearly within the pH range studied (3.5–5.8). No nodules were formed at pH 3.5.     

Genistein preincubation of Bradyrhizobium japonicum cells improves strain competitiveness under greenhouse,but not field conditions

In the soybean-B. japonicum symbiosis, genistein has been identified as one of the major compounds in soybean seed and root exudates responsible for inducing expression of the B. japonicum nodYABC operon. In this study, we have tested the possibility that genistein treatment prior to inoculation can increase the competitiveness of the treated B. japonicum strain under both greenhouse and field conditions. Two mutants of the two B. japonicum strains each with a different antibiotic resistant marker were selected. They were tested with one or the other treated with genistein. The results showed genistein treated mutants had higher levels of nodule occupancy than the untreated mutant or parent strain under greenhouse conditions. Mutants from 532C had higher nodule occupancies than mutants from USDA110, especially at 15 °C. In the more complex field environment, genistein treated mutants formed fewer nodules than the untreated mutants. The contradictory results of strain competitiveness for greenhouse and field experiments are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Screening of yeasts for cell-free production of (R)-phenylacetylcarbinol

105 yeast strains from 10 genera and 40 species were evaluated for cell-free production of (R)-phenylacetylcarbinol (PAC), the chiral precursor in the manufacture of the pharmaceuticals ephedrine and pseudoephedrine. Carboligase activity of pyruvate decarboxylase (PDC), forming PAC from benzaldehyde and pyruvate, was found in extracts of 98 strains. PAC was not formed from benzaldehyde and acetaldehyde, an activity of bacterial PDCs from Zymomonas mobilis and Zymobacter palmae. Two interesting groups of candidates were identified in the yeast screening: carboligase activities of Schizosaccharomyces pombe PDCs were very low but showed best resistance to pre-incubation with acetaldehyde and benzaldehyde; and highest carboligase activities combined with medium resistance were found in strains of Candida utilis, C. tropicalis and C. albicans.     

广州红锥-马占相思林物种组成与多样性研究

为了解广州市龙眼洞林场红锥(Castanopsis hystrix)-马占相思(Acacia mangium)阔叶混交林的群落结构,对其物种多样性进行了分析。结果表明,红锥-马占相思阔叶混交林的物种丰富度依次为乔木层灌木层草本层层间植物层。乔木层的Simpson和Shannon-Wiener指数分别为0.945和0.237,密度为2 671 ind./hm2,红锥、马占相思、三桠苦(Melicope pteleifolia)、山乌桕(Triadica cochinchinensis)和台湾相思(A. confusa)的重要值较高。灌木层中豺皮樟(Litsea rotundifolia var. oblongifolia)、九节(Psychotria asiatica)、黄牛木(Cratoxylum cochinchinense)的重要值超过10%。层间植物的优势科为茜草科(Rubiaceae),其次是夹竹桃科(Apocynaceae)。草本层植物密度约38 000 ind./hm2,以禾本科(Poaceae)占优势,有9种。红锥林从幼龄向中龄过渡,优势种群为增长型,而马占相思林则由近熟龄或成熟龄向过熟龄过渡。对不同区域4种近似林分的比较表明,混交林的生物多样性远远高于人工纯林。因此,红锥-马占相思阔叶混交林已形成了混交复层异龄林结构,乔木层、灌木层和草本层均具有较高的物种丰富度。     

Growth and nitrogen acquisition strategies of Acacia senegal seedlings under exponential phosphorus additions

There remains conflicting evidence on the relationship between P supply and biological N₂-fixation rates, particularly N₂-fixing plant adaptive strategies under P limitation. This is important, as edaphic conditions inherent to many economically and ecologically important semi-arid leguminous tree species, such as Acacia senegal, are P deficient. Our research objective was to verify N acquisition strategies under phosphorus limitations using isotopic techniques. Acacia senegal var. senegal was cultivated in sand culture with three levels of exponentially supplied phosphorus [low (200 μmol of P seedling⁻¹ over 12 weeks), mid (400 μmol) and high (600 μmol)] to achieve steady-state nutrition over the growth period. Uniform additions of N were also supplied. Plant growth and nutrition were evaluated. Seedlings exhibited significantly greater total biomass under high P supply compared to low P supply. Both P and N content significantly increased with increasing P supply. Similarly, N derived from solution increased with elevated P availability. However, both the number of nodules and the N derived from atmosphere, determined by the ¹⁵N natural abundance method, did not increase along the P gradient. Phosphorus stimulated growth and increased mineral N uptake from solution without affecting the amount of N derived from the atmosphere. We conclude that, under non-limiting N conditions, A. senegal N acquisition strategies change with P supply, with less reliance on N₂-fixation when the rhizosphere achieves a sufficient N uptake zone.     

Selection of Competitive Strains of Rhizobium Nodulating Phaseolus Vulgaris and Adapted to Environmental Conditions in Egypt,Using the Gus-Reporter Gene Technique

Two Rhizobium etli strains, EBRI 2 and EBRI 26, isolated from Egypt were tested for nodulation competitiveness on beans using Rhizobium tropici CIAT 899G as the competing strain. The insertion of the gus-reporter transposon mTn5ssgusA30 did not alter the nodulation or nitrogen fixation capacity of mutant strain CIAT 899G compared to the wild type. At neutral pH, R. etli strains EBRI 2 and EBRI 26 were more competitive than CIAT 899G with the bean cultivar Saxa. These two strains gave nodule occupancies of 52.1 and 61.1% competing with equal cell numbers of CIAT 899G. Nodule occupancies from these two native strains increased with the bean cultivar Giza 6 from Egypt to 66 and 67.5%. Based on these results, cultivar Giza 6 was used to select the most competitive strains under stress of salinity or alkalinity as a major problem for a large part of Egyptian soils. Under stress of salinity (0.2% NaCl or 34.2 mM NaCl), the salt-sensitive strain EBRI 2 was more competitive than the salt-resistant strain EBRI 26. Strain EBRI 2 gave 87.4% but strain EBRI 26 gave 63.7% nodule occupancy against CIAT 899G. The same trend of results was observed under stress of alkalinity (pH 8). Strain EBRI 2 occupied 83% while Strain EBRI 26 occupied 53.2%.     

Selective isolation of Acetobacterium woodii on methoxylated aromatic acids and determination of growth yields

Anaerobic enrichments with methoxylated aromatic compounds as substrates (vanillate, syringate, trimethoxycinnamate) were inoculated from freshwater mud and sewage sludge samples. In 12 out of 16 cultures the same type of rod-shaped, motile bacteria was selectively enriched. Two strains, NZva16 and NZva24, were isolated in pure culture and recognized as Acetobacterium woodii by comparison with the type strain (DSM 1030).All three Acetobacterium strains were able to grow with all 10 of the tested aromatic compounds containing methoxyl groups. In the presence of bicarbonate, these substrates were used as sole organic electron donors and carbon sources. UV-absorption spectra revealed that the aromatic rings were not degraded, and that the corresponding hydroxy derivatives of the methoxylated compounds were formed. The only further fermentation product formed was acetate. When equimolar concentrations of the methoxylated benzoic acid derivatives were applied, the growth yields were proportional to the number of methoxyl groups per molecule. Methoxyl groups or methanol were metabolized by homoacetate fermentation: in the presence of bicarbonate 4 mol of acetate. In case of the methoxylated cinnamic acid derivatives less acetate was formed and the corresponding hydroxy derivatives of phenylpropionic acid appeared as a result of the double bond reduction in the acrylate side chain. In comparison to the benzoate derivatives with the same number of methoxyl groups, higher growth yields were obtained with the cinnamate derivatives.     

盐磷胁迫对木麻黄和台湾相思种子萌发及幼苗生长的影响

恶劣环境下,人工海防林因面临养分胁迫而经营困难。为探讨盐、磷胁迫对主要海防林树种木麻黄和台湾相思种子萌发及生长的影响,该研究分别用不同浓度的NaCl(盐)和KH₂PO₄(磷)溶液处理种子和浇灌幼苗,测定种子萌发和幼苗生长指标。结果表明：(1)高盐胁迫显著抑制种子萌发,对幼苗生长有一定影响,但两种植物影响程度不同;台湾相思种子萌发耐盐性高于木麻黄,前者相对盐害率最大值为23.03%,后者为89.15%;随着盐浓度增加,木麻黄和台湾相思种子的发芽率、发芽势、发芽指数和活力指数均降低,对应最大值分别为38.70%、34.67%、18.70、0.055和76.67%、62.22%、48.46、6.11。(2)两种植物的株高和根长随盐浓度增加而降低,木麻黄和台湾相思株高分别为12.29～6.01 mm和48.27～17.33 mm,根长分别为8.57～1.45 mm和33.41～5.88 mm;台湾相思根、茎、叶生物量及根冠比均随盐浓度的增加逐渐减小,木麻黄各处理差异较小。(3)台湾相思的种子和幼苗较木麻黄更耐低磷环境,二者最适磷浓度存在差异;木麻黄种...