Higher Root Length Research Articles

Propagação vegetativa de porta-enxertos de pereira por estacas semi-lenhosas

Pesquisou-se a viabilidade técnica da propagação vegetativa dos porta-enxertos de pereira 'Taiwan Nashi-C', 'Taiwan Mamenashi' (Pyrus calleryana Dcne.) e 'Seleção IAC-1' (Pyrus spp.), por estacas semi-lenhosas. O experimento foi conduzido em telado equipado com sistema de nebulização intermitente, pertencente ao Núcleo de Pesquisa e Desenvolvimento do Jardim Botânico, do Instituto Agronômico (IAC), em Campinas, Estado de São Paulo. Adotou-se o fatorial 3 x 4 (porta-enxertos x doses de ácido indolbutírico), com cinco repetições de 20 estacas, em delineamento inteiramente casualizado. Com os resultados obtidos aos 60 dias após a estaquia, conclui-se que: a) é tecnicamente possível a propagação dos porta-enxertos 'Taiwan Nashi-C', 'Taiwan Mamenashi' e 'Seleção IAC-1' por estacas semi-lenhosas; b) dentre os porta-enxertos pesquisados, 'Taiwan Nashi-C' apresenta a maior porcentagem de enraizamento, a menor porcentagem de estacas com calo, além do maior comprimento de raízes e número de raízes por estaca; c) é necessário o uso de ácido indolbutírico para o enraizamento de estacas semi-lenhosas desses porta-enxertos, sendo que, no conjunto das variáveis analisadas, as concentrações de 4.000 mg.L-1 e de 6.000 mg.L-1 proporcionam os maiores benefícios ao enraizamento adventício; d) as concentrações de ácido indolbutírico testadas não são fitotóxicas às estacas semi-lenhosas dos genótipos pesquisados.

Competitive interactions between two meadow grasses under nitrogen and phosphorus limitation

Summary 1. Different grass species dominate grasslands fertilized with nitrogen (N) or phosphorus (P), possibly due to the impact of N : P stoichiometry on competitive interactions. How species compete for nutrients, and whether the mechanisms are similar for N and P, is still not fully understood. 2. We investigated whether the outcome of competition between Alopecurus pratensis and Agrostis capillaris depends on N : P stoichiometry, and on the ability to acquire supplied N or P. Monocultures and mixtures of the two species were grown in pots at nine combinations of N and P supply (N : P ratios 1·7, 15 and 135, all at three supply levels). After 3 months, we determined plant biomass, morphological traits and nutrient concentrations of plant tissues. 3. N : P supply ratios had similar effects on the growth of the two species but contrasting effects on their competitive strength, as assessed by comparing growth in competition to growth in monoculture: Alopecurus was the stronger competitor under N limitation (N : P ratio 1·7), whereas Agrostis was an equal or stronger competitor under P limitation (N : P ratio 135). This result resembled patterns of species distribution observed in the field. 4. The strong competitive response of Alopecurus at the low N : P supply ratio was associated with a high investment in root biomass and root length, and a high nitrogen productivity. The competitive response of Agrostis at the high N : P supply ratio was associated with low root mortality and high root phosphatase activity. 5. Our results obtained under N limitation support the pre‐emption theory in which plants with the highest root length are able to acquire more N from the soil than their competitors, and therefore can suppress their growth. Under P limitation, however, plant investment in root length could not explain competitor suppression. Here, other factors important in competition for P, such as mycorrhizal hyphal length, root longevity, or exudation rates of P releasing compounds, merit investigation.

CHEAPER WATER SOURCES FOR MICROPROPAGATION OF BANANA (MUSA ACUMINATE 'GRANDE NAINE')

High cost of production is one of the limiting factors for large scale adoption of the technique for commercial production. Reducing the cost factor necessarily mean low investment and that could encourage low income entrepreneurs to take up tissue culture activity as a business venture. Thus this activity could spread to towns and taluks. Banana is one crop which commands a phenomenally high demand in India. Water source in production laboratories is from distillation units. The costs of these units are a high regular maintenance is also economically taxing. Hence to reduce the cost of production of tissue-cultured banana, in vitro multiplication and rooting was carried out on a medium prepared with five different sources of water viz., filtered water (millipore), filtered water (aquaguard), double distilled water, single distilled water, autoclaved potable tap water. Cultures grown on MS medium prepared with filtered (aquaguard) water recorded maximum mean number of shoots/culture (12.50), highest mean shoot length (2.77 cm) and maximum mean number of adventitious buds/culture (8.25) followed by and millipore filtered water and autoclaved potable tap water. Microshoots cultured on MS medium prepared with aquaguard filtered water recorded highest rooting percentage (100%), maximum number of primary roots/shoots (9.50) and highest root length (7.00 cm) followed by filtered water (millipore). These results have clearly demonstrated that a cheaper source of water such as filtered (aquaguard) or even autoclaved potable tap water can be used as low cost alternative water sources for successful micropropagation of banana 'Grande Naine'.

Determination of the vegetative and reproductive characteristics of valerian (Valeriana officinalis L.) under sowing dates and planting densities in Iran

This study was conducted as split-plot field experiment in a randomized complete block design with four replications for one year planting. The main factors were the sowing dates (10th August, 1st September and 20th September) and sub factors were the planting densities (4, 8 and 12 plants/m2). The results showed that sowing date and planting density significantly affected grain yield, essential oil yield, essential oil percentage, root length, root diameter, flowering stem number and root yield. Means comparison showed that the highest grain yield and root yield were achieved under the 8 plants/m2 planting density and 10th August sowing date, the highest root length and flowering stem number were achieved under 12 plants/m2 planting density and 10th August sowing date, the highest root diameter was achieved under 4 plants/m2 planting density and 10th August sowing date, the highest essential oil yield was achieved under 8 plants/m2 planting density and 20th September sowing date and the highest essential oil percentage was achieved under 4 plants/m2 planting density and 20th September sowing date. It was thus concluded that sowing date and planting density are the main factors influencing the quantity and quality characteristics of valerian. Our finding may give applicable advice to commercial farmers and agricultural researches for management and concern on planting density strategy and estimate of sowing date carefully for increase of quantity and quality characteristics in medicinal and aromatic plants farming and is better that such studies may be validated further by conducting for two or more years. Key words: Sowing date, planting density, essential oil, valerian.

NITROGEN SOURCE AND MANGANESE APPLICATION EFFECTS ON MANGANESE DYNAMICS IN THE RHIZOSPHERE OF WHEAT CULTIVARS GROWN ON MANGANESE-DEFICIENT SOILS

To study the effect of two different nitrogen (N) sources and manganese application on root-shoot relations and manganese (Mn) dynamics in the rhizosphere of two wheat cultivars, a screen house experiment was conducted using manganese-deficient soil. Significantly higher root length (RL), root surface area, shoot dry weight (SDW), root length density, and manganese uptake were recorded in calcium nitrate supplied plants of cultivar ‘WH 542’ when applied with calcium nitrate along with manganese rather than ammonium sulfate. Cultivar ‘PD W274’ produced 72% of the maximum RL and 77% of the maximum SDW under similar conditions. Results indicated that cultivar ‘WH 542’ was more manganese efficient than ‘PD W274’ and calcium nitrate was a better source of nitrogen than ammonium sulfate. However, maximum shoot manganese content was recorded in ammonium sulfate supplied plants, which was due to depletion of manganese at root surface to a lower value, causing higher concentration gradient and hence higher manganese influx to root.

Rhizobacteria Capable of Producing ACC‐deaminase May Mitigate Salt Stress in Wheat

Rhizobacteria may promote plant growth by cleaving plant‐produced 1‐aminocyclopropane‐1‐carboxylic acid (ACC) through ACC‐deaminase activity. The effectiveness of plant‐growth‐promoting rhizobacteria (PGPR) for improving the growth and yield of wheat (Triticum aestivum L.) was evaluated under salinity stress. The effect of high ethylene concentrations on plant growth and performance of these strains for reducing this negative impact was also evaluated by conducting a classical triple‐response bioassay. Eighteen rhizobacterial strains containing ACC‐deaminase were screened by conducting a jar experiment under axenic conditions at 1 (original), 5, 10, and 15 dS m−1 The four most effective strains were further evaluated in a pot trial at salinity levels of 1.46 (original), 5, 10, and 15 dS m−1 In general, salinity depressed the growth of wheat, but inoculation improved the growth and yield of wheat compared with the uninoculated controls. At the high salinity level (15 dS m−1), plant height, root length, plant biomass, and grain yield increased up to 37, 70, 116, and 111%, respectively, compared with the control. Results indicated that inoculated plants had higher K+/Na+ ratios, relative water contents and chlorophyll content; however, relatively low proline contents compared with controls. The results also showed that intensity of the classical triple response decreased due to inoculation with these strains. Pseudomonas putida (W2) and P. fluorescens (W17) were the most effective strains for alleviating salt stress even at higher salinity levels. Our results suggest that the assay for ACC‐deaminase activity could be an efficient approach to screen effective PGPR for increasing the growth and yield of wheat under salt‐stressed conditions.

INFLUENCE OF BIO-INOCULANTS ON NURSERY ESTABLISHMENT OF PAPAYA CV. SOLO

Papaya (Carica papaya L.) grows well under tropical and subtropical conditions. The crop deserves attention due to its high nutritive value and production potentiality. In recent years, papaya is being attacked by many devastating pests and diseases particularly ring spot virus and foot rot. Preventive methods work better than curative for these biotic stresses. Hence, a study was undertaken to test the effect of four bio-inoculants on growth and performance of papaya (cv. Solo) seedlings in the nursery stage. The bio-inoculants were Endoroots soluble (1), Mycorrhiza Roots (2), Mycoplex (3) and Trichoderma. Among them, the seed germination was higher (92.18%) in treatment with Endoroots soluble at 20 g/cft of coir pith and Trichoderma 2 g/kg of coir pith, where as the treatment with Mycorrhiza Roots at 20 g/cft of coir pith media influenced most of the characters positively, viz. higher plant height (46.86 cm at 60 DAS), higher stem girth (1.90 cm at 60 DAS), more leaf area ( 99.53 cm 2 at 60 DAS), more number of roots per plant (17.06), higher root length (16.06 cm), higher fresh (4.5 g) and dry weight (0.92 g) of roots per plant. Further, the N, P and K analysis in seedlings after 60 days growth revealed that, the treatment with Mycorrhiza Roots at 20 g/cft of coir pith media accumulated higher N (3.77%), P (8.37%) and K (4.00%) in the seedlings. Thus, it can be concluded that, a combination of these bio-inoculants in the nursery media will help to get strong, healthy, disease free seedlings in the nursery.

PENGARUH NAUNGAN DAN LAMA PENYIMPANAN STEK PADA PERTUMBUHAN JARAK PAGAR (Jatropha curcas L.) DAN JARAK MERAH ( Jatropha gossypiifolia L.)

There are two species of Jatropha in East Nusa Tenggara (NTT), i.e. physic nut (Jatropha curcas L.) and red jatropha or cotton leaved physic nut (1. gossypilfolia L). Both species possess potency as traditional medicine. Propagating jatropha by seeds could not be conducted throughout the year because the seeds were produced on certain time only. On dry season in 2005, a research had conducted in Teun Village, Belu Regency, NTT for studying the effect of shading and cutting storage on the growth of the two jatropha species. This research had 12 treatments with two replications and employed Factorial Experimental Design. The data were processed by SAS (Statistic Analysis System) program. The result of this research showed that the growth of physic nut better than that of red jatropha. Light shading stimulated the growth of buds, leaves and roots of cutting of jatropha on 60 days after planting. No significant was found in the growth of buds, leaves and roots of cutting of jatropha that were directly planted and stored for four days. Cutting of both species that stored for four days and placed under light shading (with 70% of light intensity) produced higher bud growth and root length than those placed under dense shading (with 30% of light intensity).

Induction mechanism of adventitious root from leaf explants of Morinda citrifolia as affected by auxin and light quality

An efficient protocol for adventitious root induction from leaf explants of Morinda citrifolia treated with different concentrations of indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) was established in relation to physiological process changes during adventitious root induction under different light sources (fluorescent, red, blue, red + blue, and far-red). Among the different concentrations of IBA and NAA, 1.0 mg l−1 IBA was proven as the best auxin source for adventitious root induction under fluorescent light. Higher concentrations of IBA and NAA trigger callus formation in both light and dark conditions. Maximum numbers of adventitious roots were induced under red light (26) followed by blue light (22) and the lowest under far-red light (6). In contrast, numerous callus formations were induced by red + blue followed by red and blue, while the highest root length (1.66 cm) with negligible callusing was observed under fluorescent light. Catalase and guaicacol peroxidase activities were highest under red light followed by fluorescent light and the lowest under red + blue light, but superoxide dismutase activity was not significantly influenced by different light sources. Ascorbate peroxidase played an important role in detoxification of the harmful effects of hydrogen peroxide (H2O2). Under fluorescent light, significantly lower accumulation of H2O2 was observed. Accumulation of H2O2 in the induced root under different light showed a positive correlation with peroxidation of lipids and was observed higher under far-red followed by red + blue and blue light.

Morphological traits and water use strategies in seedlings of Mediterranean coexisting species

The distribution of plants is associated with their different patterns of response to their environment. Mediterranean plants have evolved a number of morphological and physiological adaptations that determine their ability to survive and grow, being an effective water uptake and use important factors for drought resistance. In this article, we evaluated interspecific differences in morphology, biomass allocation, and architectural traits and their relationship with water use strategies in seedlings of seven co-occurring Mediterranean species (Anthyllis cytisoides L., Genista scorpius L. DC., Myrtus communis L., Pistacia lentiscus L., Rosmarinus officinalis L., Spartium junceum L. and Ulex parviflorus Pourr.). The results showed that morphological root features vary among species and they are significantly correlated with root hydraulic conductance and leaf gas exchange variables. Species with high specific root length (SRL) showed a low hydraulic conductance per root length (K RRL) but high specific hydraulic conductance (K As). M. communis and P. lentiscus showed the most contrasting water use patterns with respect to the other species studied. The results are not affected when considering phylogenetic relatedness. Thus, the variability observed in root hydraulic properties and leaf gas exchange suggests important mechanisms for understanding species coexistence in water-limited ecosystems.

In vitro and ex vitro rooting of Siratia grosvenorii, a traditional medicinal plant

Since a decade, the large-scale commercial production of Siratia grosvenorii plantlets is being practiced through in vitro culture of its microcuttings, but it has some drawbacks such as handling of plantlets, low transplant-survival rate, development of massive callus, low yield after transplantation, etc. An experiment has been conducted to improve the prevailing technique as well as to develop a new ex vitro technique to overcome these drawbacks. Several concentrations of naphthalene acetic acid (NAA) (0–4.0 mg/l) have been tried with the MS (Murashige and Skoog in Physiol Plant 15:473–479, 1962) basal medium containing 3% (w/v) sucrose and 4.0 g/l agar, out of which 0.1 mg/l NAA was found best in terms of smaller diameter of callus and maximum rooting and transplant survival rate. Further, use of perlite instead of agar medium also showed possibilities for future research on commercial-scale plantlet production. Ex vitro rooting technique was found superior to the in vitro one as plantlets developed through this method had lateral roots without any callus at the base of microcuttings, just like the natural root system and of course with higher root length, rooting rates, and transplant survival rate compared to the in vitro developed plantlets. Further, this technique is economical in terms of labor and time saving and gives rise to vigorous plants which ultimately bring higher yields and profits.

Enraizamento de estacas do híbrido somático laranja 'caipira' + limão 'Volkameriano' e de seus genitores

Objetivou-se neste trabalho comparar o enraizamento de estacas do híbrido somático laranja 'Caipira' (C. sinensis L. Osbeck) + limão 'Volkameriano' (C. volkameriana V. Tennore et Pasquale) com aquelas dos seus genitores tratadas com ácido indolbutírico (AIB) (0; 500; 1.000 e 2.000 mg L-1). As estacas de laranja 'Caipira' e limão 'Volkameriano' foram retiradas de plantas obtidas a partir de sementes, e as do híbrido somático, de plantas enxertadas recém-podadas. O delineamento experimental utilizado foi um fatorial 3 x 4 (genótipos x concentrações de AIB) inteiramente casualizado, com quatro repetições de 10 estacas por repetição, totalizando 480 estacas. As estacas foram cultivadas em bandejas de poliestireno expandido, contendo substrato comercial, em estufa com sistema de nebulização intermitente, por 90 dias. A produção de plantas enraizadas foi altamente eficiente para os três genótipos avaliados, considerando-se a maioria das variáveis relacionadas ao enraizamento e vigor das estacas, independentemente do uso de AIB. Estacas de limão 'Volkameriano' apresentaram médias de comprimento e massa seca das raízes superiores às dos demais genótipos. Para todos os genótipos, as porcentagens de estacas vivas e enraizadas foram elevadas (acima de 90%), indicando o alto potencial deste germoplasma para ser utilizado na produção de mudas e porta-enxertos por estaquia.

Plant litter chemistry and mycorrhizal roots promote a nitrogen feedback in a temperate forest

Summary Relationships between mycorrhizal plants and soil nitrogen (N) have led to the speculation that the chemistry of plant litter and the saprotrophy of mycorrhizal symbionts can function together to closely couple the N cycle between plants and soils. We hypothesized that a tannin‐rich, ericoid mycorrhizal (ERM) plant promotes the retention of protein–tannin N in soil, and that this N source is accessible to saprotrophic ERM symbionts and their hosts, but remains less available to co‐occurring ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) symbionts and their hosts. We tested this feedback hypothesis in a southern Appalachian forest community composed of two microsites: a hardwood microsite with ECM and AM trees in the overstorey and understorey, and an AM herb layer; and a rhododendron microsite where the understorey and herb layer are replaced by ERM rhododendron. We synthesized 15N‐enriched protein–tannin complexes from leaf litter extracts representing each forest microsite and examined the fate of 15N in soil volumes 3 months and 1 year after the complexes were placed in the field. Protein–tannin complexes derived from the rhododendron microsite led to a higher retention of 15N in soil organic matter and a lower recovery in dissolved N pools than those from the hardwood microsite, supporting the hypothesis that rhododendron tannins create stable complexes that increase organic N retention in soils. Rhododendron complexes led to greater 15N‐enrichment in ERM roots than in AM and ECM roots, supporting the hypothesis that rhododendron can better access the N complexed by its own litter tannins than can co‐occurring forest trees and plants. Our results suggest that both fungal saprotrophy and a high specific root length contribute to the ability of ERM roots to acquire N from complex organic sources. Synthesis. This study provides evidence of an intricate N feedback where plant litter chemistry influences the cycle of N to maximize N acquisition by the host's mycorrhizal roots, while hindering N acquisition by mycorrhizal roots of co‐occurring plants. Feedback processes such as these have the potential to drive patterns in nitrogen cycling and productivity in many terrestrial ecosystems.

The role of hull in germination and salinity tolerance in some sunflower (Helianthus annuus L.) cultivars

Six different NaCl levels (0, 5, 10, 20, 30 and 40 dS m-1) and two seed types (hulled and dehulled) of sunflower seeds of Opal, Shelly (Confectionary) and Pactol (Oily) were tested to determine the effects of the hull on salinity tolerance during germination. Germination percentage (%), mean germination time (day), root and shoot length (cm) were investigated. Kernel type seeds exhibited higher germination percentage, longer root and shoot length and lower mean germination time compared to the achene type seeds at all NaCl levels. Both achene and kernel type seeds of cv. Pactol gave the highest germination percentage, root and shoot length. Hull was responsible for delaying germination and water uptake by seeds while it had no role in lowering the toxic effects of NaCl during germination. Therefore, it was concluded that inhibition in germination at all levels of NaCl was mainly due to osmotic barriers created by the presence of hulls rather than salt toxicity. Key words: Sunflower, Helianthus annuus L., hull, NaCl, cultivar, germination.

Patterns and relationships of plant traits, community structural attributes, and eco-hydrological functions during a subtropical secondary succession in central Yunnan, Southwest China

Human-induced changes in land use lead to major changes in plant community composition and structure which have strong effects on eco-hydrological processes and functions. We here tested the hypothesis that changes in traits of living plants have resulted in changes in structural attributes of the community that influenced eco-hydrological functions by altering eco-hydrological processes. This was done in the context of a subtropical secondary forest suc?cession following land abandonment in Central Yunnan (Southwest China). During the succession, species with high specific leaf area (SLA), high leaf nitrogen concentration (LNC), high specific root length (SRL), and low leaf dry matter content (LDMC) were progressively replaced by species with the opposite characteristics. The obtained results of correlation analyses were as follows: (1) Correlations were significant between community-aggregated SLA, LNC, and the leaf area index (LAI). Significant correlations were detected between LAI, canopy interception and stemflow, and surface runoff and soil erosion. (2) Significant correlations were also found between community-aggregated SLA, LNC, LDMC, and accumulated litter biomass. High accumulated litter biomass strongly increases the maximum water-retaining capac?ity of litter. However, significant correlations were not found between the maximum water-retaining capacity of litter and surface runoff and soil erosion. (3) Correlations were significant between community-aggregated SLA, LNC, and fine root biomass. Fine root biomass was not significantly related to the maximum water-retaining capacity of the soil, but was significantly related to surface runoff and soil erosion. These results suggest that canopy characteristics play a more important role in control of runoff and soil erosion at the studied site. It follows that plant functional traits are closely linked with canopy characteristics, which should be used as a standard for selecting species in restoration and revegetation for water and soil conservation.

Paenibacillus—a predominant endophytic bacterium colonising tissue cultures of woody plants

High densities of endophytic bacteria were found in plant material from poplar, larch and spruce that had been micropropagated for at least 5 years. The majority of these bacteria were assigned to the genus Paenibacillus based on the sequencing of the 16S rRNA genes. Other endophytic bacteria such as Methylobacterium, Stenotrophomonas or Bacillus could also be found but only in some tissue cultures. Certain species or strains of Paenibacillus, especially those with a close relationship to P. humicus, seemed to accumulate under in vitro conditions without visible negative influences on the plant’s development. Poplar microcuttings inoculated with the endophytic Paenibacillus isolate 22 showed significantly more roots per cutting and higher root length in comparison to the control plants after 3 weeks.

Propagação de três genótipos de abieiro (Pouteria caimito) por estaquia de ramos herbáceos

Foram selecionadas três plantas de um pomar comercial, com características agronômicas desejáveis, proveniente de propagação seminífera, que forneceram estacas herbáceas, contando com cerca de 15 cm de comprimento, um par de folhas no nó superior, corte em bisel na base e foram tratadas com 4 doses de IBA (0, 1.000, 3.000 e 5.000 mg.l-1) e, posteriormente, plantadas em caixas plásticas perfuradas contendo como substrato, vermiculita textura média. A condução do experimento foi em ambiente de 50 % de sombreamento, sob nebulização intermitente. A análise estatística foi em esquema fatorial 3X4, (genótipos X doses de IBA), com 4 repetições de 10 estacas cada. Após 90 dias foram avaliados a percentagem de enraizamento e sobrevivência, o comprimento e número médio de raízes por estaca. O IBA não influenciou as variáveis analisadas. O genótipo somente induziu mais raízes na seleção 3 e maiores raízes nas seleções 1 e 3.

Coarse root architecture of three boreal tree species growing in mixed stands

Root system architecture determines many of the vital functions of a tree, e.g. stability of anchorage and resource uptake. The shoot:root ratio is determined through the allocation of resources. Studies on below-ground architectural elements in boreal mixed forests are relatively scarce despite the fact that knowledge on below-ground interactions and allocation changes in relation to stand developmental stage and soil fertility is needed both in ecological and silvicultural research. In this study, sixty tree root systems of three different tree species, Betula pendula, Picea abies and Pinus sylvestris, were excavated in five mixed forest stands in order to quantify differences between the species and sites in terms of rooting behaviour. Root architecture differed greatly between the species, implying different solutions for the functions of root systems. Half of the P. sylvestris had developed a taproot as a response to anchorage needs, while P. abies correspondingly had pronounced secondary growth of proximal roots. Betula pendula had the most extensive root system, illustrating the greater demand of deciduous trees for water. Betula pendula was also the most sensitive to soil fertility: it favoured exploration on the poorest site, as illustrated by the high total root length, whereas on the most fertile site its strategy was to efficiently exploit soil resources through increased branching intensity. The results obtained in this study provide basic knowledge on the architectural characteristics of boreal tree root systems for use by forestry professionals and modellers.

Plants interactions between Suaeda salsa individuals are mediated by salinity stress

To test how plants interactions change with environmental stress, neighbors removal experiments in Suaeda salsa communities of beach were conducted in Hangzhou bay Zhejiang Province, China. Results showed that there is a significant shift from positive interaction in high salinity stress to negative interaction in low salinity stress. Removal experiments also clarified the role of phenotype response in linking plants interactions and environmental stress. Under low salinity stress, biomass, stem length, root length, leaf area, and photosynthesis rate, water-use efficiency of neighbors removal plants were higher than those of control plants, while leaf water content of neighbors removal plants were lower than those of control plants. Under high salinity stress, biomass, stem length, root length, leaf area, and photosynthesis rate, leaf water content of neighbors removal plants were lower than those of control plants, while water-use efficiency of neighbors removal plants were higher than those of control plants. It can be concluded that S. salsa interactions were mediated by salinity stress through morphological and physiological plasticity.

Influence of phosphorus supply on two cowpea varieties grown on an acidic Alumi-Haplic-Acrisol

The effect of phosphorus (P) supply on two cowpea (Vigna unguiculata) genotypes (Epace 10 and Santo Inacio) was studied. Seedlings received 0, 30 and 100 mg Pkg−1 on 3-kg P-deficient acid Alumi-Haplic-Acrisols inoculated with arbuscular mycorrhizal (AM) fungi. Biomass production, root length, AM infection rate, nodulation, flowering, grain yield and P, Ca, Mg and Al contents were evaluated. At 31 days after sowing (DAS), the cultivars were affected by P limitation without differences in development. At 70 DAS, Epace 10 had higher root length, biomass production and flowered earlier with 0-P than Santo Inacio. At 122 DAS, Epace 10 produced higher grain yields than Santo Inacio. High (60%) AM-colonization was observed with 0-P although colonization, and shoot-P, -Mg and -Ca concentrations were insignificantly (p < 0.05) different among genotypes. With 30 and 0 mg kg−1 P-supply, Santo Inacio accumulated higher shoot Al (300 – 600 mg kg−1DM) than E 10 (100 – 400 mg kg−1DM), suggesting Epace 10's higher capacity for Al exclusion under P-deficient conditions.