Similar Total Biomass Research Articles

Subsurface irrigation with ceramic emitters improves greenhouse tomato yield and resource utilization efficiency by stabilizing soil hydrothermal status

Maintaining a stable and suitable soil hydrothermal status is crucial for promoting the high quality and yield of greenhouse vegetables throughout the year. Irrigation by regulating soil moisture changes to soil heat capacity is an effective measure to alleviate the fluctuation of soil hydrothermal environment caused by interannual solar radiation. To investigate the soil hydrothermal status of greenhouse tomatoes under subsurface irrigation with ceramic emitters (SICE) and its impact on tomato growth and yield, we conducted a two-season greenhouse experiment with subsurface drip irrigation (SDI) as a control. The results showed that soil hydrothermal changes under SICE fluctuated less with time in the autumn and spring experiment than SDI; SICE could increase soil temperature in the tomato root zone profile in winter and decrease the profile temperature in summer. This indicates that SICE could reduce the direct effect of air temperature on soil temperature and maintain a stable and suitable soil hydrothermal condition. Furthermore, the underground and vegetative biomass of SICE stopped increasing with the rapid growth of water and heat resources to the inflection point. They shifted to the accumulation of reproductive biomass. However, the vegetative biomass of SDI continued to increase in the late stage of water and heat resources. Therefore, under similar total biomass conditions, SICE obtained more output. SICE increased tomato yields by 11.60 in autumn and 8.36 t hm−2 in spring compared to SDI. The regulation mechanism also improved the hydrothermal resource utilization efficiency under SICE, with SICE increasing water and heat resource use efficiency by 24.04 % and 3.73 % (in autumn) and 9.80 % and 6.00 % (in spring), respectively, compared to SDI. We conclude that SICE is an effective and promising irrigation method for greenhouse tomato cultivation for stabilizing the soil water and heat environment, promoting yield, and improving the utilization rate of solar radiation.

Crop attributes explaining current grain yield dominance of maize over sorghum

Yield genetic gains have been significantly higher for maize ( Zea mays L.) than for sorghum ( Sorghum bicolor L. Moench ). Today there is questioning under which environments sorghum is a better option than maize, since maize has increased its tolerance to water and N limitations. For this we conducted eleven rainfed experiments at different sites around the central region of Argentina, using representative commercial genotypes of each crop. Experiments involved different sowing dates and N fertilization treatments, generating a total of 21 growing conditions where both crops were simultaneously compared. Measured traits included yield, phenology, leaf area development, light interception, and biomass accumulation. Explored growing conditions yielded from 1.8 to 11.7 Mg ha −1 for maize, and from 1.4 to 9.9 Mg ha −1 for sorghum. Crops yield difference (maize minus sorghum) ranged from − 0.3 to 4.8 Mg ha −1 , and this difference significantly favoured maize in all growing conditions except one. As expected, the yield difference in favor to maize increased in magnitude in the environments with more positive water balance (r: 0.54; p < 0.01) and higher N levels (r: 0.43; p < 0.05). When compared to maize, sorghum always showed a longer time to anthesis and a shorter grain-filling duration, higher LAI, lower post-anthesis biomass accumulation, and similar total biomass at physiological maturity. Maize harvest index was higher and less variable than the sorghum one (0.44 to 0.56 and 0.28 to 0.45, for maize and sorghum, respectively). A comparison with previous literature showed that the cut-off yield (i.e., maize yield below which sorghum has better yield performance) is significantly lower than expected. Results reinforce previous evidences highlighting that the differential research investment in the two crops is limiting the capacity of sorghum to out-yield maize across environments. • Maize and sorghum were simultaneously grown across a wide environmental range. • Maize out-yielded sorghum in mostly all growing environments. • The yield where maize was out-yielded by sorghum was 1.8 Mg ha −1 only. • Maize has a shorter vegetative period, a higher post-flowering growth, and a higher harvest index.

Small-scale environmental variations drive vegetation structure and diversity in Amazon riverine forests

Riverine forests in the Brazilian Amazon provide a series of ecosystem services and harbor one of the world's most diverse floras, but the main drivers of variation in small spatial scales in such tropical forests are not well understood. Our aim was to evaluate tree community structure and diversity patterns in the Teles Pires River to identify the main drivers of small-scale variations in the area. We sampled 4,180 individuals from 49 botanical families, 164 genera and 347 species by using six transects of five pairs of 50 m x 40 m permanent plots totalizing 60 permanent plots in a 12-hectare area. We utilized generalized linear mixed models to assess whether the effects of the environmental variables in the vegetation structural parameters. Altitude and groundwater depth were the main drivers influencing species diversity patterns. The trees had similar total biomass in areas within the same distance from the river margins. There was a lower species richness and tree density closer to the river margins. Otherwise, we found larger trees (higher individual biomass) closer to the river margins when compared to areas distant from the margins. Our results indicate a high species turnover from the river margins to the forest interior, which highlights the importance of assessing local effects on biological communities in tropical forests, especially in the Brazilian Amazon where several high-impact dams are planned.

Community structure and ecosystem carbon stock dynamics along a chronosequence of mangrove plantations in China

Mangrove plantations exhibit a high potential for biomass carbon sequestration, however, their effects on soil organic carbon (SOC) accumulation remains unclear. We examined the dynamics of community structure and ecosystem carbon accumulation along a chronosequence of Sonneratia apetala plantations on Qi’ao Island, China. To reveal the self-thinning pattern of S. apetala plantations, 114 quadrats were randomly established in the S. apetala plantations. Four quadrats were selected for soil sampling from differently-aged (4, 9, and 15 years) S. apetala plantations, a 15-year-old S. apetala + Bruguiera gymnorrhiza plantation and a 40-year-old mature Kandelia obovate community. We found that the self-thinning process happened in these S. apetala plantations. The vegetation biomass was found to significantly increase with forest age and the 15-year-old S. apetala and 15-year-old S. apetala + Bruguiera gymnorrhiza plantations had similar total biomass as the 40-year-old K. obovate community. Notably, SOC content and stocks only showed a minor increment along the chronosequence of S. apetala plantations, and SOC stock of the 15-year-old S. apetala community was less than 60% of that of the 40-year-old K. obovate community. The 15-year-old S. apetala + B. gymnorrhiza community had a similar biomass value as the 15-year-old S. apetala community, but the former community had a significant higher SOC stock than the latter. Biomass increment and SOC accumulation are unsynchronized with mangrove plantation development, and monospecific mangrove plantations may not be able to significantly accelerate SOC sequestration in the early plantation stage. Multi-specific plantations may facilitate SOC accumulation more than monospecific plantations.

Success of native and invasive plant congeners depends on inorganic nitrogen compositions and levels

Abstract Aims Successful plant invaders usually exhibit three strategies: Jack-of-all-trades (more robust in stressful sites), Master-of-some (more responsive in favorable sites) and Jack-and-master (both robustness and responsiveness). To revisit these strategies, we examined how soil inorganic nitrogen (N) compositions and levels influence the success of native and invasive plant congeners in the context of plant communities. Methods We conducted an experiment involving three fixed factors: species origin, N composition and N level. Here, we selected 21 plant species (eight pairs of invasive and native congeners and five non-congeneric natives) to assemble plant communities, which were subject to nine N environments consisting of three N compositions (3:1, 2:2 and 1:3 NO3−/NH4+) and three N levels (low, medium and high N). We determined the following metrics: total biomass, relative biomass (a proxy of species success), mortality rate and mortality time. Important Findings Across nine N environments, native and invasive congeners exhibited similar total biomass, relative biomass and mortality time, but invaders had a marginally lower mortality rate than natives. Similar success between native and invasive congeners was linked to their similar growth and tolerance. N compositions influenced mortality time and N levels affected the total biomass and relative biomass. Importantly, species origin, N composition and N level interactively affected the total biomass, relative biomass and mortality time. These findings suggest that native and invasive plant congeners may be similarly successful across different N environments, and that inorganic N compositions and levels both contribute to plant invasion success.

Variations of the biodiversity and carbon functions of karst forests in two morphologically different sites in southwestern China

Abstract Knowledge of the biodiversity and carbon (C) functions of karst forests is scarce. This study comprehensively compared the species diversity and floristic characteristics, biomass and its allocation, leaf and soil C and nitrogen (N) concentrations, and photosynthetic capacity of dominant tree species between peak clump depression (PCD)-type and plateau surface (PS)-type karst forests on the basis of two large plots (i.e., 1 and 2 ha, respectively) in southwestern China. Results showed that PCD-type karst forest exhibits higher biodiversity and more tropical family and genus types than PS-type karst forest. These two types of karst forest presented similar total biomass, but PCD-type karst forest allocated more biomass to supporting roots and less biomass to absorbing roots. PS-type karst forest had higher C/N ratios in leaves and soils than PCD-type karst forest. Deciduous tree species in PS-type karst forest had low net photosynthetic rates, resulting in lower net photosynthetic rate in PS-type karst forest than in PCD-type karst forest. Species richness and C storage in the karst morphologies would be considerably enhanced if degraded vegetation in different types of karst area could be successfully restored to forests according to respective morphological and vegetation features. A comprehensive understanding of the biodiversity and C functions of karst vegetation is essential to biodiversity conservation, regional C storage estimation, vegetation management and restoration, and potential global change mitigation.

Profitability and Sustainable Use of Traps for Amazon Shrimp (Macrobrachium amazonicum) From the Amazon River

The objective of this study was to evaluate the profitability, productivity and selectivity of traps used for the capture of freshwater prawn using different spacings between the laths. This study was developed in the estuary of the Amazon River near Santana island, Amapá, Brazil. Collections were conducted using traps called “matapi”, which are cylindrical shrimp traps made with wooden slats or laths, with funnel-shaped entrances at both sides, and the spacings between the laths ranged between 1 to 10 mm in 1 mm increments. Each trap was covered with a net called a “sobrematapi”, or trap cover. The length of carapace in centimeters and the weight in grams were measured for all specimens. The shrimp were categorized into small, medium, and large size classes. Selectivity curves were used to determine selectivity for the different lath spacings. Traps with lath spacing below 7mm should be considered as being predatory because they allow for the capture of small individuals, with more than 50% of these being captured using spacings from 1 to 5mm. Despite the fact that spacings between 8 and 10mm captured lower quantities of shrimp, this enabled the capture of larger specimens with a similar total biomass yield, and this spacing is considered to be the most ecologically and economically viable. In order to minimize the capture of young shrimp without drastically affecting economic yield, it is suggested that shrimp trap lath spacings be above 6mm.

Evolution of increased intraspecific competitive ability following introduction: The importance of relatedness among genotypes

Abstract A long‐standing explanation for invasion success is that invasive plants could evolve to be more competitive following introduction. This evolution of increased competitive ability (EICA) hypothesis, however, has seldom been tested with regard to intraspecific competition. Given that plants can display different responses to related and unrelated conspecifics, the evolution of intraspecific competitive ability might be specific to genotypes of different relatedness. Here, we grew five native (South American) and five introduced (North American) genotypes of the clonal herbaceous invasive plant Alternanthera philoxeroides alone, with above‐ground competition from kin (the same genotype) or from one of two types of strangers (another genotype from the same range or another genotype from the other range). When grown alone, introduced and native genotypes produced similar total biomass and storage‐root biomass. However, in response to intraspecific competition, introduced genotypes showed increases in total biomass and stem length, and a decrease in specific stem length, whereas native genotypes showed the opposite pattern. When grown with kin instead of strangers, introduced genotypes showed an increase in branch number, whereas native genotypes showed the opposite. Synthesis. Our study provided evidence for evolution of increased intraspecific competitive ability in an invasive plant. We also found, for the first time, that the interactions among kin were likely to shift from competition towards facilitation following introduction.

Earthworm functional traits and interspecific interactions affect plant nitrogen acquisition and primary production

We performed a greenhouse experiment to test how the functional diversity of earthworms, the dominant group of soil macro-invertebrates in many terrestrial ecosystems, affects nitrogen cycling and plant growth. Three species were chosen to represent a range of functional traits: Lumbricus terrestris (large, mainly detritivorous, makes vertical permanent burrows open at the surface), Aporrectodea longa (medium-large, feeds on both detritus and soil, makes burrows more branched than L. terrestris), and Allolobophora chlorotica (small, geophagous, makes ephemeral burrows below the soil surface). Mesocosms with ryegrass (Lolium perenne) were inoculated with none to all three species (similar total biomass), using an experimental design (Simplex) suited to partition single species and diversity effects. Two contrasting N sources, urea or mammalian dung, were labelled with 15N so that the acquisition by plants and earthworms and recovery of applied 15N could be estimated.Over 3 months, plant production was higher with urea applications, but there were also species-specific earthworm effects: A. chlorotica and, to a lesser extent, A. longa increased shoot biomass, whereas L. terrestris increased root biomass. Earthworms did not affect soil N concentrations or leaching losses, whereas more N was leached under urea. A. chlorotica tended to increase dung-15N recovery in grass shoots, but in interaction with A. longa had the opposite effect, possibly through increased N immobilization in the microbial biomass. Earthworms assimilated negligible amounts of urea-15N but a substantial proportion (17% on average) of the dung-15N, with no clear-cut differences between species. Our findings show that earthworm species may have similar trophic response to N sources and yet different effects on plant N uptake and primary production, and that inter-specific earthworm interactions can result in non-additive diversity effects.

Interaction between plant density and nitrogen management strategy in improving maize grain yield and nitrogen use efficiency on the North China Plain

SUMMARYUnderstanding the physiological mechanisms of biomass accumulation and partitioning in the grain, and the nitrogen (N) uptake associated with different plant densities and N management strategies, is essential for achieving both high yield and N use efficiency (NUE) in maize plants. A field experiment was conducted in 2013 and 2014, using five rates of N application and three plant densities (6·0, 7·5 and 9·0 plants/m2) in Quzhou County on the North China Plain (NCP). The objective was to evaluate whether higher plant density can produce more biomass allocated to the grain to achieve higher grain yield and to determine the optimal N management strategies for different plant densities. The highest grain yield and NUE were achieved in the 7·5 plants/m2 treatment; both the sub-optimal (6·0 plants/m2) and supra-optimal (9·0 plants/m2) plant densities resulted in diminished yield and NUE. Compared to 6·0 plants/m2, the 7·5 plants/m2 treatment displayed higher biomass accumulation during the grain-filling period and also exhibited more biomass allocated to kernels with similar total biomass accumulation compared with the 9·0 plants/m2 treatment, which contributed to its higher grain yield. The N uptake in the 7·5 plants/m2 treatment was similar to that in the 9·0 plants/m2 treatment up to pre-silking. However, the post-silking N uptake of the 7·5 plants/m2 treatment was 66·4 kg/ha, which was 29·1% higher than that of the 9·0 plants/m2 treatment. Furthermore, the highest maize grain yield was achieved in the 0·7 × optimal N rate (ONR × 0·7), ONR and ONR × 1·3 treatments for 6·0, 7·5 and 9·0 plants/m2, respectively, which suggests that different N management strategies are needed for different plant densities. In conclusion, selecting a planting density of 7·5 plants/m2 with an in-season root zone N management is a potentially effective strategy for achieving high grain yield and high NUE for maize production on the NCP.

The effects of cultivar and nitrogen management on wheat yield and nitrogen use efficiency in the North China Plain

Understanding the inherent characteristics of cultivars with different spike types based on biomass and biomass partitioning with optimal nitrogen (N) management is important to achieve both high wheat yield and N use efficiency (NUE). A field experiment was conducted over 3 years using five N rates and two winter wheat cultivars (a larger spike cultivar (TN) and a multiple spike cultivar (LX)) in the North China Plain (NCP) to evaluate whether larger spike cultivar can accumulate more post-anthesis biomass and achieve higher yields and to determine the optimal N management strategies for the two cultivars. In both cultivars over 3 years, the optimal N rate (ONR) based on in-season root zone N management (INM) reduced the N rate by 140kgNha−1 from 300 to 160kgNha−1 without any yield losses, while it increased the N uptake efficiency from 32% to 64% compared with typical farmer's N practice (FNP). Furthermore, under ONR treatment, the grain yield and N physiological efficiency of TN significantly was higher 6 and 10% over 3 years than that of the multiple spike cultivar LX, respectively. The yield increase of TN was attributed mainly to the increased harvest index (7%) and similar total biomass. The higher 11% leaf N concentration at anthesis and 10% grain number m−2 of TN significantly increased the post-anthesis biomass by 24% under ONR, which played an important role in increasing the harvest index (HI). In addition, the grain yield of 70% ONR significantly decreased by 12% and 8% for TN and LX over 3 years, respectively, while no significant increase in grain yield was observed for 130% ONR, suggesting that the ONR was optimal in practice. Changes in N management may not be required for the two cultivars, because the ONR according to INM is close to the economically optimal N rate (EONR) based on grain yield response curves. In conclusion, selecting a larger spike cultivar with optimal N management could be a useful strategy to achieve high yield and high NUE for wheat production in the NCP, especially using optimal crop management practices.

The effects of defoliation on carbon allocation: can carbon limitation reduce growth in favour of storage?

There is no consensus about how stresses such as low water availability and temperature limit tree growth. Sink limitation to growth and survival is often inferred if a given stress does not cause non-structural carbohydrate (NSC) concentrations or levels to decline along with growth. However, trees may actively maintain or increase NSC levels under moderate carbon stress, making the pattern of reduced growth and increased NSCs compatible with carbon limitation. To test this possibility, we used full and half defoliation to impose severe and moderate carbon limitation on 2-year-old Quercus velutina Lam. saplings grown in a common garden. Saplings were harvested at either 3 weeks or 4 months after treatments were applied, representing short- and longer-term effects on woody growth and NSC levels. Both defoliation treatments maintained a lower total leaf area than controls throughout the experiment with no evidence of photosynthetic up-regulation, and resulted in a similar total biomass reduction. While fully defoliated saplings had lower starch levels than controls in the short term, half defoliated saplings maintained control starch levels in both the short and longer term. In the longer term, fully defoliated saplings had the greatest starch concentration increment, allowing them to recover to near-control starch levels. Furthermore, between the two harvest dates, fully and half defoliated saplings allocated a greater proportion of new biomass to starch than did controls. The maintenance of control starch levels in half defoliated saplings indicates that these trees actively store a substantial amount of carbon before growth is carbon saturated. In addition, the allocation shift favouring storage in defoliated saplings is consistent with the hypothesis that, as an adaptation to increasing carbon stress, trees can prioritize carbon reserve formation at the expense of growth. Our results suggest that as carbon limitation increases, reduced growth is not necessarily accompanied by a decline in NSC concentrations. Therefore, a lack of NSC decline may not be evidence that reduced tree growth under cold or water stress is caused by sink limitation.

A comparison of the net ecosystem exchange of carbon dioxide and evapotranspiration for treed and open portions of a temperate peatland

Net ecosystem exchange of carbon dioxide (NEE) and evapotranspiration (ET) were measured at open and treed portions of a temperate ombrotrophic bog using the eddy covariance technique to examine the potential influence of plant community characteristics on peatland carbon and water vapour exchange. The sites were located 2.7km from each other within the same peatland complex and thus experienced similar weather. Both sites were characterized by a Sphagnum ground cover and a shrub layer with similar total biomass. However, at the treed bog, 35% of this understory vascular plant layer was made up of Picea mariana (<0.5m tall) compared to less than 0.2% in the open bog. The treed bog was also characterized by an overstory dominated by a patchy distribution of stunted P. mariana. Over a single year, net CO2 uptake and ET was lower at the treed bog (NEE: −72gCm−2year−1 and ET: 449mmyear−1) than at the open bog (NEE: −104gCm−2year−1 and ET: 493mmyear−1). Chamber measurements revealed that P. mariana was associated with low rates of net primary productivity (NPP) compared to the relatively more productive ericaceous and deciduous shrubs. Although the presence of a P. mariana overstory increases both the total aboveground biomass and leaf area index in this peatland, P. mariana appears to be important in reducing both ecosystem-scale carbon sequestration and water vapour loss.

Registration of ‘HoCP 91–552’ Sugarcane

‘HoCP 91–552’ (Reg. No. CV‐143, PI 659990) sugarcane (a complex hybrid of Saccharum officinarum L., S. spontaneum L., S. barberi Jeswiet, and S. sinense Roxb. amend. Jeswiet) was released as a feedstock for an emerging bioenergy industry by the USDA‐ARS working cooperatively with the Louisiana State University Agricultural Center, and the American Sugarcane League, Inc. HoCP 91–552 is a progeny of the cross LCP 81–10 × ‘CP 72–356’ made at Canal Point, FL in 1986; it was selected at Houma, LA; its permanent name was assigned in 1991. HoCP 91–552 was dropped from the sugarcane selection program in 1997 because its fiber content was unacceptable for the Louisiana sugarcane industry, but it was reevaluated as a feedstock for the bioenergy industry in three replicated yield trials harvested from 2003 to 2007. After 11 harvests, HoCP 91–552 produced 84, 11.3, and 14.3 Mg ha−1 cane, sugar, and fiber, respectively, compared with 68, 9.5, and 10.3 Mg ha−1 cane, sugar, and fiber, respectively for the commercial standard ‘LCP 85–384.’ When compared with ‘L 79–1002,’ HoCP 91–552 produced significantly more sugar, less fiber, and similar total biomass. HoCP 91–552 is resistant to brown rust (caused by Puccinia melanocephala H. and P. Sydow), leaf scald [caused by Xanthomonas albilineans (Ashby) Dowson], and mosaic diseases (caused by Sugarcane mosaic virus and Sorghum mosaic virus) and is moderately resistant to smut disease (caused by Ustilago scitaminea H. and P. Sydow) and the sugarcane borer (Diatraea saccharalis F.). Release of HoCP 91–552 gives growers a new choice as a feedstock for the production of biofuel.

Genetic and phenotypic differences between thistle populations in response to habitat and weed management practices

Rapid evolutionary change is increasingly being recognized as commonplace, but the evolutionary consequences for species and ecosystems under human-induced selection regimes have not been explored in detail, although many species occur in such environments. In a common garden experiment and with amplified fragment length polymorphism markers, we examined whether genetic differentiation has taken place between spatially intermixed populations of creeping thistles Cirsium arvense (Asteraceae) collected from a natural habitat (maritime shores), a semi-natural habitat (road verges) and arable fields under two management regimes: conventional and organic farming. Populations of C. arvense have altered genetically and locally adapted their growth patterns with changed land use. Although plants from different habitats showed similar total biomass production, shoot and root production was higher for maritime populations, suggesting selection for increased competitive ability. Competitive ability then declined in the order semi-natural, conventional farms and organic farms. Thistles in arable fields may be more selected for tolerance against disturbances from herbicides and mechanical weed control. In addition, early shoot sprouting and genetic analysis showed differentiation between plants originating from conventional farms and farms that were converted to organic 9–30 years ago, suggesting some adaptation to altered crop cultivation practices.

Nitrogen and Phosphorous Removal by Ornamental and Wetland Plants in a Greenhouse Recirculation Research System

A nutrient recirculation system (NRS) was used to assess the ability of four ornamental and three wetland plant species to remove nitrogen (N) and phosphorous (P) from stormwater runoff. The NRS was filled with a nutrient solution with total N and P concentrations of 11.3 and 3.1 mg·L−1, respectively, to simulate high levels of nutrient contaminations in stormwater. Nutrient removal abilities of herbaceous perennial ornamental plants, canna (Canna ×generalis Bailey) ‘Australia’, iris (Iris pseudacorus L.) ‘Golden Fleece’, calla lily [Zantedeschia aethiopica (L.) Spreng], and dwarf papyrus (Cyperus haspan L.) were compared with those of wetland plants arrow arum [Peltandra virginica (L.) Schott], pickerelweed (Pontederia cordata L.), and bulltongue arrowhead (Sagittaria lancifolia L.) in three experiments. ‘Australia’ canna had the greatest water consumption, total biomass production, and aboveground N and P content followed by pickerelweed. ‘Golden Fleece’ iris had higher tissue N concentrations than canna but much lower biomass production. Dwarf papyrus had similar total biomass as pickerelweed but less shoot biomass. N and P removed from the NRS units planted with canna (98.7% N and 91.8% P) were higher than those planted with iris and arrow arum (31.6% and 31.5% N, and 38.5% and 26.3% P, respectively). NRS units planted with dwarf papyrus had similar nutrient recovery rate as pickerelweed, but much less total N and P were removed as a result of less water consumption. The NRS units planted with calla lily had lower nutrient removal than canna and pickerelweed. Our results suggest that canna is a promising ornamental species for stormwater mitigation, and harvesting the aboveground biomass of canna can effectively remove N and P from the treatment system. However, more research needs to be done to evaluate factors that might affect plant performance in a floating biofiltration system.

Interactive Effects of Carbon Dioxide and Water Stress on Potato Canopy Growth and Development

Reductions in potato (Solanum tuberosum L.) canopy growth are observed with mild water stress. Potato growth is enhanced by elevated atmospheric carbon dioxide ([CO2]), but interactions of [CO2] and water stress on canopy formation and dry matter partitioning have not been studied. Two soil‐plant‐atmosphere research (SPAR) experiments were conducted at 370 or 740 μmol mol−1 [CO2] and six different irrigations from 10 to 100% of the daily water uptake of the control. Increases in plant length from 23 to 111 cm at 60 d after emergence (DAE), leaf appearance duration from 38 to 71 d, leaf appearance rate from 0.5 to 0.93 leaves d−1, individual leaf area from 50 to 175 cm2, and lateral branch elongation were observed as irrigation increased. Values were generally smaller for elevated [CO2] plants under water stress. Biomass increased with irrigation from 73 to 346 g plant−2. The percentage allocated to the canopy increased with irrigation from 50 to 80% in ambient and 30 to 80% in elevated [CO2]. Despite decreased canopy size, elevated [CO2] plants produced similar total biomass, but higher yield, at most irrigations. Reduced canopy mass in elevated [CO2] plants was attributed to suppressed lateral branch development due to an interactive effect of [CO2] and water stress on tuber sink strength. These results indicate that water stress predicted by climate change models will be mediated somewhat under [CO2] enrichment.

Compatibility of silver barb Puntius gonionotus (Bleeker) with Indian major carps in a grow-out polyculture

The compatibility and growth performance of silver barb Puntius gonionotus (Barbonymous gonionotus) with the three Indian major carps, i.e., Catla catla, Labeo rohita and Cirrhinus mrigala, were assessed in a 10-month carp polyculture trial. Treatments T-1, T-2, T-3 and T-4 were stocked with three of the above four carp species, with an absence of silver barb, mrigal, rohu and catla, respectively, while all four species were stocked in treatment T-5. The treatments were stocked at 6000 fingerlings ha−1, with an equal species ratio maintained in each treatment. Incorporation of silver barb into the polyculture system neither affected the survival of any carp irrespective of species combination nor yielded significant changes in biomass production among treatments, except for the one without catla, where it was significantly low. The study revealed a higher extent of competition between silver barb and rohu, perceptible from the lower growth of one in the presence of the other. Although a certain level of competition of silver barb with mrigal was evident, competition with catla was not perceptible. Irrespective of species combination with silver barb as a component species, similar total biomass production in treatments revealed the feasibility of its incorporation into the Indian major carp-based polyculture practice without affecting the total yield.

Infection by the systemic fungus Epichloë glyceriae and clonal growth of its host grass Glyceria striata

Many plant species have the ability to expand laterally through space by clonal growth. Plant pathogens can affect clonal growth characteristics thereby altering the success of host plants within populations and of clonal species within communities. We conducted a greenhouse experiment to determine the effects of the systemic fungal pathogen, Epichloe glyceriae, on clonal growth patterns of its host grass, Glyceria striata. We found that infected and uninfected plants produced similar total biomass and numbers of tillers plus primary stolons per mother ramet. However, biomass allocation to tillering (vegetative growth) vs stolon production (clonal growth) was significantly affected by pathogen infection. Infected plants produced more stolons and clonal growth biomass than uninfected plants while mother ramets of uninfected plants produced more tillers and biomass than infected plants. Stolon architecture of infected and uninfected plants also differed. In two of three populations, infected plants produced stolons with greater biomass and shorter spacer lengths, even though mean stolon lengths were similar for infected and uninfected plants. These results contrast strongly with most other clonal plant-pathogen systems where infected plants are less vigorous and have reduced clonal growth compared to uninfected plants. Greater clonal growth may be an effective mechanism for host genotypes to persist and spread when seed production is prevented, as is the case with castrating pathogens like Epichloe glyceriae.

Resource re‐allocation following fruit removal in cucurbits: patterns in cantaloupe melons

SUMMARYThe effects of removal of fruits of marketable size on investment to male, female and vegetative activities., were evaluated using cantaloupe melons, Cucumis melo L., cv. Retata Degli Ortolani. Leaf and flower demography were used to examine the dynamics of potential trade‐offs among these activities. Treated plants and controls had similar total biomass, but it was distributed differently. Treated plants had more vegetative biomass, both above ground and in roots, whereas control plants allocated more, in both absolute and proportionate terms, to fruits. Treated plants produced more leaves than controls, but individual leaf life expectancies were the same. Developing fruits on control plants thus seem to act as sinks at the expense of new leaves. Fruit removal also significantly stimulated production of male flowers and fruit, though these fruits contained significantly fewer, and smaller, seeds. Once fruit removal had begun, lability of floral sex expression was evident. In treated plants there was a significant increase in the production of male flowers. Both treated and control plants produced the same number of pistillate flowers; adjustments of fruit production occurred because of differences in the rate of successful fertilization, and later, differences in fruit set. In control plants (but not in treated plants) there were obvious tradeoffs between yield components. The costs of fruit maturation in treated plants appeared to be decoupled from other yield components.