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351.
Glomalin-related soil protein (GRSP), a glycoprotein of arbuscular mycorrhizal fungi (AMF) secreted into soil, governs the aggregate stability, but the role of GRSP in soil and plant water is sparsely studied. The 24-week-old red tangerine (Citrus tangerina) inoculated with Glomus etunicatum and G. mosseae were subjected to a soil drying for 12 days as soil water deficit (SWD). Length of SWD significantly reduced mycorrhizal colonization, soil hyphal length, and leaf and soil water potential (Ψ), but increased total GRSP (T-GRSP), easily extractable GRSP (EE-GRSP), and proportion of water-stable aggregates (WSAs) in >0.25 mm size, irrespective of AMF source. The AMF-inoculated seedlings showed significantly higher T-GRSP, EE-GRSP, and leaf/soil Ψ than non-AMF seedlings during SWD. A significantly positive correlation was observed for mycorrhizal colonization versus leaf or soil Ψ, and hyphal length versus leaf Ψ, suggesting that root intra- and extra-radical hyphae participated in water transport. Interestingly, in GRSP fractions, only T-GRSP was significantly positively correlated with 0.25–1 and >0.25 mm WSA and negatively with leaf and soil Ψ. These results revealed a strong glue function of T-GRSP (not EE-GRSP and hyphae) to alter the proportional distribution of WSA size, thereby aiding toward prevention of soil water loss for improving soil–plant water relations.  相似文献   
352.
The influence of different fertilization practices [i.e., nitrogen (N), phosphorus (P), and potassium (K) fertilizers, crop residue, and manure] on dry matter production of white yam (Dioscorea rotundata) “kokoro” a late variety of yam, tuber biomass and dry matter distribution to the plant parts was determined in upper Oueme basin (Republic of Benin) in the years 2001, 2002 and 2003. The experimental design was a randomized complete block with four replications. Altogether there were eight plots divided into two groups consisting of four plots each, one was treated with manure (at the rate of 10 ton ha?1), second plot with mineral fertilizer (N30:P30:K60), third plot with combination of manure and mineral fertilizer, whereas the fourth plot was left as control (no application of fertilizer). In year 2002 and 2003 the same combinations were made taking crop residues (at the rate of10 ton ha?1) from external sources as a source of organic matter at the place of manure. Manure application did not have a significant effect on yam total biomass production nor on tuber yield when applied on fields after fallow. Whereas crop residue application had a positive significant effect on yam tuber and total biomass production when applied after cotton and maize and with adequate rainfall amount and distribution. Regarding partitioning pattern in yam crop, no effect of different practices of fertilization has been noticed. The crop behaves identically (i.e, partitioning rate) in both fertilized and unfertilized management practice.  相似文献   
353.
Foliar fertilization and microbe supplemented iron (Fe) bioavailability can fulfill iron demand of plants. An experiment was performed to examine the effect of Psuedomonas fluorescens along with foliar spray ferrous sulfate on low-chill peach plants suffering from iron deficiency. Number of leaves per shoot, leaf area, chlorophyl content, Fe: Mn ratio of leaves, fruit yield and fruit physico-chemical parameters were recorded. The results showed a significant increase in leaves chlorophyl content, iron: manganese ratio of leaves, fruit yield, fruit length, fruit breadth, total soluble solids (T.S.S) and T.S.S and acid ratio with the inoculation of Pseudomonas fluorescens as well as foliar spray of ferrous sulfate, whereas, acidity of fruit pulp was decreased. Significantly higher number of leaves per shoot was also noted with foliar spray of ferrous sulfate. Pseudomonas fluorescens inoculation along with foliar spray of ferrous sulfate significantly increased leaves chlorophyl content, fruit length, T.S.S and T.S.S : acid ratio of fruit pulp.  相似文献   
354.

Context

In tropical landscapes, dominant land-use changes involve conversion of intact forest to an agricultural matrix with embedded fragments of remnant forest. However, most research to date has focused on how these land-use changes affect species within the fragmented ecosystem, rather than the flux of energy and nutrients within these different landscape elements.

Objectives

We examined how forest fragmentation and conversion to orange fields impact the potential for litter decomposition in a Costa Rican landscape, in particular via effects on macroinvertebrates (MIs) and microclimate.

Methods

We measured mass losses of a standard leaf litter in four habitats: orange fields, small forest fragments, large forest fragments and intact forest. Litter bags were constructed of mesh that either excluded or allowed MIs. Decomposition rates were measured in wet and dry seasons, and at different distances from the forest edge.

Results

Forest fragmentation and forest conversion had divergent effects on decomposition rates. Decomposition rates were 7 % slower in forest fragments during the dry season than in intact forest, and this result was mediated by forest fragmentation effects on MIs. Decomposition rates were 9 % higher in orange fields during the wet season, relative to intact forest, and this pattern was explained by effects of the litter microenvironment on leaching rates or smaller invertebrates. Fragment area and distance from forest edge had minor or undetectable effects on decomposition in fragments.

Conclusions

We conclude that land-use changes affect decomposition processes in both forest and agroecosystems, and these effects can vary in mechanism and direction across disturbed landscapes.
  相似文献   
355.
The roots of Terminalia alata yielded three new glycosides: 3,3'-di-O-methylellagic acid 4-O-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranoside (1), 5,7,2'-tri-O-methylflavanone 4'-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranoside (2), and 2alpha,3beta, 19beta,23-tetrahydroxyolean-12-en-28-oic acid 3-O-beta-D-galactopyranosyl-(1-->3)-beta-D-glucopyranoside-28-O-beta-D-glucopyranoside (3). Compounds 2 and 3 displayed antifungal activity.  相似文献   
356.
Seasonal variation in the biomass and total non-structural carbohydrate content (TNC) of fine roots of teak (Tectona grandis L. f.) were studied in 19- and 29-year-old plantations in a dry tropical region. Fine root TNC content was highest during the dry summer (May), and lowest in the early part of the rainy season (July). Generally, seasonal trends in TNC content were the opposite of those in fine root biomass. The TNC concentration of roots increased with diameter and decreased with soil depth. In the 19-year-old plantation, fine root TNC content was approximately 12% higher than in the 29-year-old plantation.  相似文献   
357.
Periodic variations in the concentration, deposition and canopy impact of different forms of N on annual N deposition through rainfall, throughfall and stemflow in 5 and 8 year old stands of Casuarina equisetifolia were studied. Throughfall and stemflow ranged from 70 to 76% and 5–6% of annual precipitation respectively. The total N deposition by rainfall was 11.1 kg ha−1 year−1, and by throughfall was 13.6 kg ha−1 year−1 and 16.5 kg ha−1 year−1 in 5-year-old and 8-year old plantations, respectively. The quantities of N deposited through stemflow in the two plantations were nearly identical, accounting for 1.6 kg ha−1 year−1. Observations of the monthly deposition of NH4,N, NO3-N, Kjeldahl-N and organic-N revealed that maximum deposition occurred in July and the minimum in September. Organic-N deposition was 17% less (5-year) than the rainwater content. Net deposition of N, as an effect of canopy, was 7–8.7 kg ha−1 year−1, which was added directly to the available nutrient pool of soil.  相似文献   
358.
Micromorphology indicates that soils of the central part of the Gangetic Plains are polygenetic. They occur on surfaces originating at 13 500, 8000, 2500, >500 and <500 BP (QGH5 to QGH1, respectively). The QGH5 soils on upland interfluves show degraded illuvial clay pedofeatures of an early humid phase (13 500–11 000 BP) and thick (150–200 μm) microlaminated clay pedofeatures of a later humid phase (6500–4000 BP). The earlier clay pedofeatures were degraded by bleaching, loss of preferred orientation, development of a coarse speckled appearance and fragmentation, whereas those of the later phase are thick, smooth and strongly birefringent microlaminated clay pedofeatures. The illuviation was more extensive during the later phase, as indicated by enrichment of groundmass as discrete pedofeatures of clay intercalations. Pedogenic carbonate was formed during the intervening dry phase from the early Holocene to 6500 BP. It forms irregularly shaped nodules of micrite and diffuse needles with inclusions of soil constituents. The subsequent change to wetter conditions caused dissolution–reprecipitation, which resulted in partial to complete removal of carbonate from soils over large areas.  相似文献   
359.
The physical properties of okra seed were evaluated as a function of moisture content (m.c.). The average length, breadth and thickness of the seed varied from 5·92 to 7·30, 4·71 to 5·40 and 4·59 to 5·36 mm, respectively, as the moisture content increased from 8·16 to 87·57% d.b. The roundness and sphericity increased from 77·76 to 79·35% and 74·48 to 76·52%, respectively, with increase in moisture content from 8·16 to 19·56% d.b. and then decreased to 72·39 and 70·63%, respectively, with further increase of moisture content. In the moisture range of 8·16–87·57%, the seed volume increased from 0·067 to 0·124 cm3, 1000 seed weight, W1000 from 65·78 to 129·75 g and the angle of repose from 27·60 to 39·47°. The bulk density, true density and porosity decreased from 0·592 to 0·558 g cm−3, 1·107 to 0·986 g cm−3 and 46·34 to 43·20%, respectively, in the moisture range from 8·16 to 87·57% d.b. The static coefficient of friction increased on four structural surfaces namely, aluminium (0·390–0·484), bakelite (0·345–0·480), galvanised iron (0·368–0·493) and mild steel (0·389–0·480) as the moisture content increased from 8·16 to 87·57% d.b.  相似文献   
360.
Rainwater samples (N = 51) were collected at Rampur, an areafree from anthropogenic activity during the monsoon of 1997 and1998. The concentration of ions follows a general pattern as Ca> NH4 > Mg > SO4 > Cl > F >Na > NO3 > K > HCOO >CH3 COO. The pH of precipitation ranges between 5.9 and 7.4. The levels of Ca and Mg at this site are higher than otherremote sites, probably dominated by particles of soil origin.Good correlation between Ca, NO3, SO4, HCOO and CH3COO indicate that a fraction of NO3, SO4, HCOOand CH3COO may be derived from soil or associated with Ca and Mg after neutralization. The order of neutralization factorCa (2.19) > NH4 (1.26) = Mg (1.26) indicates that majorneutralization occurred by Ca. Factor analysis suggested thatCa, Mg, Na, K, NO3, SO4, HCOO and CH3COO arecontributed by soil. NH3 is known to exist as(NH4)2SO4, NH4NO3 and NH4Cl. Theymay be formed in the atmospheric water droplets by scavenging ofaerosols and reaction of gaseous species.  相似文献   
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