Tropical Leguminous Trees Research Articles

Humid tropical leguminous tree and pasture grass responsiveness to vesicular-arbuscular mycorrhizal infection

Humid tropical leguminous tree and pasture grass responsiveness to vesicular-arbuscular mycorrhizal infection

Humid tropical leguminous tree and pasture grass responsiveness to vesicular-arbuscular mycorrhizal infection

Phosphorus is the major nutrient limiting plant growth in a Costa Rican silvopastoral system located on an acid, high P-retaining, volcanic soil. We investigated plant responsiveness to vesicular-arbuscular mycorrhizal (VAM) inoculation using the leguminous tree species Erythrina berteroana Urban, and the two dominant grass species Paspalum conjugatum Berg and Homolepsis aturensis Chase of this silvopastoral system. We grew grass seedlings in the greenhouse for 15 weeks in a methyl bromide-sterilized study soil to which either mixed-species VAM inoculum (Theobroma cacao feeder roots) or autoclave-sterilized cacao roots (non-inoculated control) were added. E. berteroana was grown from both seedlings and vegetative stakes (40 cm long) for 30 and 19 weeks, respectively. Upon harvest, we measured above and below ground biomass, N and P content, root∶shoot ratio, legume nodulation, and VAM infection levels. The total above-ground and root biomass of mycorrhizae-inoculated P. conjugatum seedlings were 2.5 and 2.8 times greater than those of noninoculated seedlings. In contrast, VAM-inoculated seedlings of H. aturensis produced 8.4 and 5.9 times more total above-ground and root mass than noninoculated seedlings. Mycorrhizae-inoculated E. berteroana seedlings produced 10.6 times greater shoot biomass for inoculated versus noninoculated seedlings, while E. berteroana vegetative stakes exhibited a negative growth response to VAM inoculation (an approximately 16% decrease in shoot biomass for VAM-inoculated cuttings). The difference in responsiveness between Erythrina growth forms is hypothesized to reflect the cost-benefit relationship between plant host and fungal symbiont for energy and nutrient reserves.

Host Range of the Mesquite Cutworm, Melipotis indomita (Lepidoptera: Noctuidae), a Potential Biocontrol Agent for Mesquite (Prosopis spp)

Abstract The mesquite cutworm, Melipotis indomita (Walker), is the major defoliator of mesquite in central Texas. In the laboratory, the cutworm larvae developed normally on honey mesquite (P. glandulosa Torrey var. glandulosa) and the Argentine vinal (P. ruscifolia Grisebach). Velvet mesquite (P. velutina Wooton), western honey mesquite (P. g. var. torreyana (Benson) Johnston), the Mexican P. laevigata (H. and B. ex. Willdenow) Johnston and P. juliflora (Swartz) DC, and the Argentine P. flexuosa DC were slightly less suitable hosts. Larvae developed occasionally on a natural hybrid of the Argentine P. alba Grisebach from Tucson, Arizona, but not on a commercial P. alba hybrid developed in southern Texas. Larvae did not develop on the two screw-bean mesquites tested (P. pubescens Bentham and P. reptans Bentham var. cinerascens (A. Gray) Burkart) or on 12 other species of woody legumes from central Texas, although an occasional larva fed for a few days on some of them. Among 11 species of mostly tropical leguminous trees tested, larvae developed and produced adults normally on manila tamarind (Pithecellobium dulce (Roxburgh) Bentham) and one adult was produced on monkeypod (Samanea saman (Jacquin) Merrill). In a biological control program, the mesquite cutworm would complement the damage from other foliage feeders that could be introduced from South America. It could be a candidate for introduction into other countries where mesquite has become a pest, provided that a foliage feeder were the type of control agent wanted.

Nitrogen mineralization patterns of leaf-twig mixtures from tropical leguminous trees

Green manure applications in alley cropping systems often include twigs despite their potential to absorb (immobilize) nitrogen (N). To assess the impact of twigs on net N mineralization or immobilization from hedge row cuttings, we separated cuttings fromCalliandra calothyrsus andGliricidia sepium into leaf-only, twig-only, and mixed (leaf + twig) fractions and incubated them with moist soil in the laboratory. Soil extractable inorganic N did no differ among treatments after two weeks, but after four and eight weeks was greatest in leaf-only, and least in twig-only treatments. After two weeks, extractable N from the leaf-only treatment rose steadily, while that from the twig-only and mixed treatments was variable due to periods of net mineralization and net immobilization. The pattern of variation in mixed treatments paralleled that of twig-only, indicating that net immobilization in the mixture was largely caused by the presence of twigs. Extractable N from the mixture was somewhat lower than that predicted from the sum of leaf-only and twig-only treatments. We conclude that twigs in green manure reduce short-term N availability to associated crops in agroforestry systems.

New sources of high-temperature tolerant rhizobia for Phaseolus vulgaris L.

Common bean (Phaseolus vulgaris L.) represents an important crop in tropics, but previous screenings of Rhizobium leguminosarum bv. phaseoli did not show strains that could fix N2 in symbiosis with bean at temperatures higher than 35°C (Hungria and Franco, 1993). However, there are other rhizobia and bradyrhizobia species that nodulate some tropical leguminous trees and can fix N2 at high temperatures. In a trial of rhizobial strains isolated from leguminous trees, we found that 14 out of 21 isolates from Gliricidia, Lonchocarpus and Leucaena were also able to nodulate common beans at optimal temperatures (28/23°C, day/night). When we exposed beans inoculated with these strains to high temperature conditions, 40°C/8 h/day, some of them accumulated at flowering time as much or more N as bean plants receiving mineral N. These broad host-range sources of rhizobia capable of fixing nitrogen with bean at high temperature seem to have the potential to improve yields in tropical soils.

Effects of chemical composition on nitrogen mineralization from green manures of seven tropical leguminous trees

Green manures from seven tropical leguminous trees were incubated with soil to determine the rates and controls of net nitrogen release. Fresh green manure (leaves and succulent twigs) was mixed with moist soil and incubated in polyethylene bags. Net N mineralization from green manures was estimated by the accumulation of extractable ammonium and nitrate minus the accumulation in soil alone. Patterns of N mineralization were complex, differed among species, and at 12 weeks ranged from 10 to 65 percent of original green-manure N. Cumulative net N mineralization was negatively correlated with initial soluble polyphenol content in the early phases of decomposition (1 through 8 weeks) and with initial lignin content in later phases (4 through 12 weeks). Neither initial percent N nor lignin: N ratio were strongly correlated with N mineralization. The best chemical index of N release was the initial polyphenol: N ratio. This study confirms previous findings that N mineralization from tropical legumes is controlled more by soluble polyphenols than by lignin or N content.

Leaf development in the tropical leguminous tree Copaifera in relation to microlepidopteran herbivory

Changes in sesquiterpene hydrocarbons, total phenolic compounds, astringency, total nitrogen, water content, leaf specific weight and toughness were monitored in five stages of leaf development in greenhouse-grown saplings of Copaifera pubiflora, C. officinalis and C. venezuelana var. laxa and six stages from adult trees of C. langsdorfii. In all species the phenolic content, astringency, nitrogen and water content decreased whereas the leaf specific weight and toughness increased as the leaf attained maturity. The pattern of sesquiterpene variation during leaf development, however, differed among the species. These analyses of changes in leaf development on adult trees of C. langsdorfii are related to preliminary field studies of microlepidopteran (oecophorid) herbivory in woodland sites in southeastern Brazil.

Annual, Seasonal and Diel Variation in Nitrogen Fixing Activity by Inga jinicuil, a Tropical Leguminous Tree

Patterns in nitrogen-fixing activity by Inga jinicuil Schl., a leguminous shade tree in Mexican coffee plantations, were monitored over a three-and-half year period using acetylene reduction. Year to year variation was unexpectedly large; mean annual fixation equalled 35 kg N ha-' yr-', which constitutes a significant nitrogen input to the coffee ecosystem. Nitrogen-fixing activity occurred throughout the year but was highest during the summer and autumn when precipitation and temperature were at a maximum and when the majority of tree growth and reproduction occurred. I. jinicuil flowered twice annually and nodular activity peaked once during each reproductive cycle, with maximum activity after flowering in the first reproductive cycle and before flowering in the second. Diel fluctuation in nitrogen fixation rates were obtained on most but not all sampling dates, but the observed patterns of activity varied from date to date. Aside from an activity peak that occurred at 1900 hours, averaged rates of nodular activity were remarkably constant throughout the day. Nodules from seedlings fixed 35% more nitrogen than 30-yr-old-trees but had a similar diel activity pattern. Overall, the results show that variability in nitrogen-fixing activity was large between years, pronounced but explainable between months, and relatively small between hours of the day. The timing of maximum and minimum activity, both seasonally and daily, differed significantly from what has been reported for most other nitrogen-fixing species.

15N2 Fixation and H2 Evolution by Six Species of Tropical Leguminous Trees

The C(2)H(4)/(15)N(2) and H(2)/(15)N(2) ratios for six species of tropical leguminous trees are reported. C(2)H(4)/(15)N(2) ratios ranged from 2.4 to 4.7; values for the H(2)/(15)N(2) ratios were between 0.6 and 1.4. Relative efficiency values, based on C(2)H(2) reduction, (15)N incorporation, and H(2) evolution during (15)N incorporation varied between 0.68 and 0.84 for the six species. Overall, approximately 30% of the electron flow through nitrogenase was used for H(2) evolution.

SOME UNUSUAL CHARACTERISTICS OF NITRATE REDUCTION IN ERYTHRINA SENEGALENSIS DC.

SummaryThe characteristics of nitrate reduction exhibited by the tropical leguminous tree Erythrina senegalensis differ in several respects from those of other higher plants. Nitrate reduction in this species can best be characterized as being a high activity‐low affinity system. High levels of nitrate reductase can be demonstrated using in vivo (50 to 278 μmol h−1 g fresh wt−1) or in vitro (360 μmol h−1 g fresh wt−1) assay procedures. The enzyme extracted from leaf tissue can utilize both NADH and NADPH as electron donors. The enzyme has a low affinity for nitrate, Kspp194 8 to 10 mM. The NADH and NADPH activities co‐chromatograph using several chromatographic procedures, suggesting a single molecular form of nitrate reductase is present.

Vegetative Response to Photoperiod in the Tropical Leguminous Tree Hymenaea courbaril L

Hymenaea courbaril, a widely distributed tropical leguminous tree, was used in two experiments to compare the effects of photoperiod on vegetative growth and leaf resin chemistry and to examine the role of photoperiod in ecotypic differentiation. Seedlings grown from seeds collected in five different populations which span the latitudinal range of the tropics were used in both experiments. In experiment 1, using natural light in the greenhouse, seedlings grown for one year under tong photoperiod treatments (LP) had an average stem length twice that of seedlings grown under an eight-hour photoperiod treatment (SP). In experiment 2, seedlings were grown under four photoperiods of nine hours of daylight in the greenhouse plus 50 ft-c light extensions. Average total stem lengths were nearly identical for plants in all treatments. In LP plants growth nearly ceased during the winter but resumed in the spring. A LP/SP ratio based on average stem length for each population was correlated with latitude of seed origin suggesting ecotypic differentiation. Leaf resin composition was unaffected by photoperiod. Ecological implications of these responses are discussed. Also because the importance of photoperiodism in tropical plants generally has tended to be dismissed in reviews and textbooks, a literature review emphasizing physiological mechanisms of response and ecological roles under tropical conditions is inctuded. STUDY OF THE TROPICAL LEGUMINOUS GENUS H3menaea (subfamily Caesalpinioideae) was initiated in our laboratory from a survey of resin-producing plan.ts through geologic time which showed that copious production of these compounds occurred predominantly in subtropical and tropical environments (Langenheim 1969, 1972, 1975). Because most of the current knowledge of resin-producing plants was from tem.perate-zone conifers, Hymenaea was selected as an example of a tropical angiosperm genus for an intensive ecological and evolutionary investigation of resin synthesis. This amphi-Atlantic genus, which includes 14 species (Lee and Langenheim 1975), seemed a highly appropriate choice because the Leguminosae are one of the most important resin-producing families and the subfamily Caesalpinioideae contains some of the most prominent components of New World and African rain-forest ecosystems (Langenheim 1973). Furthermore, it was evolutionarily interesting because of the occurrence of New World Hymenaea resins (am.ber) from the Tertiary epoch (Langenheim 1963, 1969) and ecologically because the species have radiated throughout the major tropical lowland ecosystems. One species, H. courbaril, has a remarkable distribution, not only essentially coincident with the New World distribution of the genus, but also occurring across the same range of ecosystems (fig. 1 ). Its occurrence in such a wide variety of habitats and considerable morphological and chemical variation led to the postulation of ecotype differentiation with respect to several environmental factors. Photoperiod is one factor in the physical environmen,t to which a widespread and variable species such as H. courbaril might become differentiated. Likewise, variation in resin chemistry between local populations led to consideration of possible ecological significance of this variation. Therefore, a comparative study of the effects of photoperiod on vegetative growth and resin chemistry of populations of H. courbaril was designed, and results emphasizing the chemical experiments have been reported previously (StLbblebine, Langenheim, and Lincoln 1976). In our collaborative work with Dr. Harry Borthwick, a pioneer authority on plant photoperiodism, we becaine aware of the importance of photoperiodism in tropical plants being generally dismissed in textbooks and reviews by many plant physiologists (Pauly 1958, Vaartaja 1959, Salisbury 1963, 1965, Salisbury and Ross 1969, Steward 1968, Mohr 1972, Meyer et al. 1973, Leopold and Kriedermann 1975); however, with notable exceptions (McClelland 1924, Avim 1964, Longman 1969, Longman and Jenik 1974). Also relatively few ecologists have pointed out its potential significance (see Daubenmire 1974: 233), and none of the above reviews or textbooks emphasizes the relationships between the physiological mechanisms of plant photoperiodism and the possible roles these responses have in tropical ecosystems. Therefore, here we are reviewing somne of the literature concerning the concepts of photoperiodism in plants, the physiological mechanisms of these responses, and their ecological roles under tropical conditions. The results of our experiments with H. courbaril are discussed in this context. 18 BIOTROPICA 10(1): 18-29 1978 This content downloaded from 207.46.13.14 on Sat, 16 Apr 2016 04:35:55 UTC All use subject to http://about.jstor.org/terms

Nature of the phytoalexin produced by alfalfa in response to fungal infection

A phytoalexin was isolated from alfalfa ( Medicago sativa) leaves by the drop-diffusate technique using spore suspensions of Helminthosporium turcicum as inoculum. The phytoalexin was identified as (−)-3-hydroxy-9-methoxypterocarpan (demethylhomopterocarpin), a compound previously isolated from several tropical leguminous trees. The identification was made on the basis of the mass spectrum, proton magnetic resonance spectra of both the phytoalexin and its monoacetate, infrared and ultraviolet spectra and the physical constants.