Reproductive Biomass Research Articles

The Fate of Bryophyte Sporophytes-Phenology and Vectors of Buxbaumia viridis in the Kalkalpen National Park, Austria.

Knowledge about the epixylic moss Buxbaumia viridis has increased significantly due to the monitoring obligation under the Habitats Directive. However, there are still open questions about its dispersal, as the wind plays a limited role in forest ecosystems, and vectors have been suspected but not yet studied systematically for this species. Here, we present data on potential vectors of Buxbaumia viridis collected for the first time with the help of cameras, completed by monitoring the fate of sporophytes during their life cycle in the Limestone Alps National Park in Austria over a period of two years. Young, green sporophytes appeared mainly in autumn, with the highest number in October. Most of them survived winter and spring but did not exceed the age of 14 months. The sharpest decline in capsules occurred in summer when mature, and the lowest number of sporophytes appeared at the end of August. Most likely, mice seem to be responsible for this loss, as the photos from the wildlife cameras suggest, and should be considered both as predators and vectors. Birds should be considered as vectors, too. In summary, most of the reproductive biomass is sacrificed in favor of more effective dispersal, including over longer distances.

Soil temperature drives elevational patterns of reproductive allometry in a biodiversity hotspot

Understanding the geographic patterns of reproductive allocation helps in clarifying the selective forces that shape the reproductive strategies of plants. However, studies on the elevational patterns of reproductive allocation remain limited. Moreover, although soil attributes have long been suspected to drive elevational patterns of reproductive allocation, few studies have explored this relationship. Delaying reproduction and allocating a high proportion of biomass to vegetative organs may be risky for plants living under high-elevation habitats, as these two processes can potentially lead to plant reproductive failure due to the low temperatures and short growing seasons at high elevations. Thus, we hypothesize that reproductive effort will increase with elevation and the elevational pattern of reproductive allocation will be largely driven by soil attributes, given their covariation with elevation. To test these hypotheses, we determined the vegetative and reproductive biomass of individual Impatiens arguta (Balsaminaceae) plants across 12 populations in the Gaoligong Mountains (China), and collected data on soil temperature, nutrients, moisture, and pH for each population. Based on standard major axis regression and linear regression models, we found that (1) both vegetative and reproductive biomass decreased with elevation; (2) all populations demonstrated significant allometric slopes (i.e., linear coefficients of log[reproductive biomass] − log[vegetative biomass] regressions) > 1; (3) allometric slopes decreased with elevation; and (4) soil temperature was a better predictor of the allometric slope than elevation, i.e., the allometric slope decreased with soil temperature. These results suggest that plant species growing at high elevation invest proportionately more resources to reproduction as an adaptation to low-temperature environments, and reproductive output is heavily dependent on vegetative growth. This study provides the first evidence of soil temperature driving reproductive allocation patterns, which suggests that plant species will favor allocation to growth under increasing soil temperatures with climate warming.

Cotton production during the tropical monsoon season. II – Biomass accumulation, partitioning and RUE in response to boll loss and compensation

Abstract Growth and reproductive structure retention in cotton (Gossypium hirsutum) is dependent on light intensity, which is often irregular in tropical environments due to shading from cloudiness associated with the monsoon. The objective of this study was to evaluate the potential effects that cloudiness-induced reproductive organ abscission and compensatory responses might have on cotton growth, partitioning and conversion of radiation to biomass (radiation use efficiency RUE) as this was unknown for the monsoon tropics. Cotton cultivars representing different morphology were sown in field experiments at closely timed intervals during the early monsoon over 5 seasons to expose crops to varying amounts of cloud-related shading, creating a matrix of crop responses. In paper I, final boll number was strongly linked with lint yield, and boll retention on the early and late flowering sympodia and yield were correlated with the radiation environment during flowering. Grouping sowing time treatments that had a similar intra-canopy distribution of bolls at maturity provided a mechanism to compare yield recovery post boll loss and consider causal factors. Maximum crop biomass ranged from 1232−1933 g m−2. Lint yield was correlated with the fraction of total biomass present as bolls (P Differences in biomass partitioning between cultivars were minor. When cloud cover abated, extended concurrent vegetative and reproductive growth enabled yield recovery. Greater LAI was a consequence of compensatory processes following fruit loss. Faster development of LAI in response to the monsoon during early flowering could further shade lower canopy fruiting sites, exacerbating fruit abscission and impacting yield compensation. RUEg (glucose equivalent) of 2.35 & 2.63 g MJ−1 PAR was comparable with cotton grown in temperate environments but declined when lower canopy fruit abscission followed by extended concurrent growth altered the ratio of vegetative vs reproductive biomass partitioning. Cloudiness poses a dichotomy of challenges for crop management during the tropical monsoon season. After cloudiness-induced fruit loss, extended concurrent growth when the radiation environment improves must be encouraged to enable the initiation of new fruiting sites for yield recovery. However, expansionary canopy growth in response to cloud and fruit loss may exacerbate detrimental shading of the lower canopy and detract from later yield recovery. Therefore management tactics including the use of irrigation, nutrient and growth regulant inputs must achieve an appropriate balance between vegetative and reproductive components during compensatory growth.

Reduced crop sowing density improves performance of rare arable weed species more effectively than reduced fertilisation

AbstractCharacteristic arable weed species of dryland cereal fields have undergone significant declines, due to agricultural intensification, to the point that some of them are considered rare. Crop edges host higher abundances of arable weed species, therefore they may act as a refuge for the conservation of these rare arable species. Using mesocosms, we experimentally tested how conditions at field edges (i.e. lower sowing densities and less intensive fertiliser applications) operate on the growth (biomass and height) and reproduction (reproductive biomass and flower onset) of six rare arable species. We found the rare arable species achieved lower biomass when growing with wheat compared with growing alone, and biomass of most of species was lower under high wheat sowing density than under low sowing density. In contrast, fertiliser application affected only two of the six arable species tested, especially when they were growing alone. Although the time to flowering was not affected by the conditions tested, reproductive biomass showed the same trends as overall biomass. These results indicate that conservation of rare arable species must primarily consider reductions in crop competition to increase their biomass and reproductive ability.

Coexpression of Sucrose Synthase and the SWEET Transporter, Which Are Associated With Sugar Hydrolysis and Transport, Respectively, Increases the Hexose Content in Vitis vinifera L. Grape Berries.

The sugar content of grape berries is affected by many factors. To explore the hexose content in different cultivars, the photosynthesis, vegetative, and reproductive biomass, as well as the enzyme activities and expression levels of genes related to sugar metabolism and sugar contents were measured. Samples were collected 70–110 days after anthesis (DAA), from Riesling (RI), Petit Manseng (PM), and Cabernet Sauvignon (CS) berries cultivated in the field. The results indicated that high expression levels of VvSWEET15 and VvSS3 and a high activity of sucrose synthase (SS) are associated with a higher hexose content in the berries of PM than in the berries of the other two cultivars. These genes promoted hexose accumulation in the berries by regulating sugar hydrolysis and transport. The results of this study indicate that active sugar hydrolysis and transport increase the hexose content of PM berries, which provides insights for grape berry quality improvement and breeding projects in wine production.Main Conclusion: The active VvSS3, sucrose synthase (SS), and VvSWEET15 increases the hexose content in Petit Manseng berries, which are associated with sugar hydrolysis and transport.

How plant allometry influences bud phenology and fruit yield in two Vaccinium species.

Understanding how plant allometry, plant architecture and phenology contribute to fruit production can identify those plant traits that maximize fruit yield. In this study, we compared these variables and fruit yield for two shrub species, Vaccinium angustifolium and Vaccinium myrtilloides, to test the hypothesis that phenology is linked to the plants' allometric traits, which are predictors of fruit production. We measured leaf and flower phenology and the above-ground biomass of both Vaccinium species in a commercial wild lowbush blueberry field (Quebec, Canada) over a 2-year crop cycle; 1 year of pruning followed by 1 year of harvest. Leaf and flower phenology were measured, and the allometric traits of shoots and buds were monitored over the crop cycle. We hand-collected the fruits of each plant to determine fruit attributes and biomass. During the harvesting year, the leafing and flowering of V. angustifolium occurred earlier than that of V. myrtilloides. This difference was related to the allometric characteristics of the buds due to differences in carbon partitioning by the plants during the pruning year. Through structural equation modelling, we identified that the earlier leafing in V. angustifolium was related to a lower leaf bud number, while earlier flowering was linked to a lower number of flowers per bud. Despite differences in reproductive allometric traits, vegetative biomass still determined reproductive biomass in a log-log scale model. Growing buds are competing sinks for non-structural carbohydrates. Their differences in both number and characteristics (e.g. number of flowers per bud) influence levels of fruit production and explain some of the phenological differences observed between the two Vaccinium species. For similar above-ground biomass, both Vaccinium species had similar reproductive outputs in terms of fruit biomass, despite differences in reproductive traits such as fruit size and number.

Impact of grazing intensities on reproduction patterns of elm trees (Ulmus pumila) in degraded sandy lands in China.

The effect of grazing on patterns of reproduction in trees has been little reported. We explored the effects of grazing intensities on reproductive growth, allocation patterns, and duration in elm trees (Ulmus pumila L.) at the Horqin Sandy Land, a degraded area in northern China. Current-year shoots were selected from branches and harvested from individual elm trees subjected to one of four grazing intensities (heavy, moderate, light, and no grazing). Shoots, flower buds, flowers, seeds, leaf buds, and leaves were collected, dried, and weighed. Results showed that the biomass in heavy, moderate and light grazing treatments is significantly higher than in no grazing treatment (P < 0.05). The reproductive allocation of U. pumila in heavy grazing treatment was significantly higher from that in the no grazing treatment (P < 0.05). Additionally, we found that reproduction of U. pumila ended later in grazed plots, suggesting the duration of reproduction is extended with grazing disturbance. Our findings suggest that U. pumila may prolong it s duration of reproduction and alter its reproductive biomass in response to grazing. It is not clear whether these effects are related to damage to U. pumila trees by grazers or whether they are due to grazers affecting soil properties or plant competitors around U. pumila trees.

Factors responsible for yield improvement in new Gossypium hirsutum L. cotton cultivars

The factors responsible for yield progress can be analysed through yield determinant frameworks. These conceptual models consider factors such as crop growth dynamics, partitioning of vegetative and reproductive biomass and yield components to provide insights into the factors responsible for observed genetic gains and opportunities for future gains. The aim of this study was to use direct cultivar comparison to assess the rate of genetic gain in the CSIRO (Australia) cotton breeding program, and to understand how factors within a conceptual yield determinant framework relate to yield performance. Using field experimentation, yield progress of 16.1 kg lint ha−1 y−1 was observed in ten cultivars released between 1968 and 2012. This study identified that selection pressure has resulted in improvements in total dry matter (TDM), harvest index (HI), lint percentage and carbon assimilation. While gains have been made in these four parameters, improvements in lint yield have largely been driven by altering HI through increasing lint percentage. Although improvements have been made in TDM, the reproductive allocation of total biomass and the amount and efficiency of light capture has not been altered in modern cultivars. Future gains in lint yield will require the concurrent maintenance of harvest index while producing larger plants with more fruiting branches that capture more incident radiation with increased efficiency. As the collection of phenotype data such as biomass, boll number, boll size and radiation use efficiency at the scale required in a commercial breeding program is largely aspirational, we conclude in the short term improvements may be achieved through direct selection for yield. Future efforts should be placed in increasing early season growth rates, and in the longer term enhancing carbon assimilation rates. Importantly, due to trait associations and the effects of trade-offs between functional components, factors within a conceptual framework must not be considered in isolation.

Phosphorus Application Improves the Cotton Yield by Enhancing Reproductive Organ Biomass and Nutrient Accumulation in Two Cotton Cultivars with Different Phosphorus Sensitivity

Phosphorus (P) plays a pivotal role in cotton by enhancing the reproductive growth and yield formation. Cotton cultivars vary greatly in response to P availability, especially under P-deficient conditions. So, we hypothesized that the increasing P level promotes the reproductive growth in cotton cultivars varying with P sensitivity. For this, two cotton cultivars, Lu-54 (sensitive to low P) and Yuzaomian-9110 (tolerant to low P), in response to three different P levels (P0: 0 (control), P1: 100, and P2: 200 kg P2O5 ha−1) were studied at 39, 52, 69, 83, and 99 days after transplanting during 2017 and 2018. The results revealed that the seed cotton yield was improved in P1 and P2 treatments by 23.9%–34.5% and 30.8%–52.3% in Lu-54, and 16.6%–25.6% and 20.6%–38.5% in Yuzaomian-9110 during 2017 and 2018, respectively. The accumulation of reproductive organ biomass was 21.0%–52.1% and 28.5%–56.8% higher in Lu-54 and 24.2%–56.8% and 34.8%–69.1% higher in Yuzaomian-9110 in P1 and P2 over the control, respectively. During the fast accumulation period, the average accumulation of N, P, K, and biomass across the years in P2 were recorded as 0.75, 0.6, 0.5, and 120.5 kg ha−1 d−1 in Lu-54, while they were 0.65, 0.5, 0.8, and 98.5 kg ha−1 d−1 in Yuzaomian-9110. Overall, a longer period, in terms of reproductive biomass accumulation, was recorded for Yuzaomian-9110 compared with Lu-54 in 2017 and vice versa across the 2018 growing season. The results suggested that increasing P rate improved yield, reproductive organ biomass, as well as nutrient accumulation in both cotton cultivars. However, low P-sensitive cultivar (Lu-54) was more responsive to P application compared with low P-tolerant cultivar.

Analysis of Grain Yield Differences Among Soybean Cultivars under Maize–Soybean Intercropping

Shading created by intercropping reduces the photosynthetic capacity of soybean plants but also directly affects the pod setting process of soybean. However, which of the changed aspects induce the yield differences in intercropped soybean cultivars is still unknown. Four soybean cultivars with similar yield and growth and development processes in monoculture were selected by a pre-experiment. Field experiments were carried out from 2015 to 2017 to investigate the leaf photosynthetic parameters, total biomass, reproductive characteristics, yield and yield components of soybean. The yield of soybean cultivars was significantly decreased in intercropping systems and the yield of cultivars (cvs.) ZH39 and QH34 were considerably higher than those of cvs. HD19 and HD20. Besides, the pod and seed number and harvest index were also reduced by intercropping and the yield components of cvs. ZH39 and QH34 in intercropping were significantly higher than those of cvs. HD19 and HD20, other than the seed size. Although the parameters of leaf photosynthetic capacity (leaf area index, net photosynthetic rate, and chlorophyll content) of soybean were changed by intercropping, there was no significant difference among cultivars. Additionally, the CGRR1–R5 (crop growth rate between R1 and R5) of intercropped soybean was lower than that of monoculture, while no significant differences were observed in different cultivars. The reproductive biomass at R5 was significantly different among soybean cultivars, and the reproductive partitioning and seed set efficiency of different cultivars were varied by the reproductive biomass at R5. Therefore, high-yielding cultivars in intercropping can achieve higher yield due to more reproductive structures survived at R5.

Effects of increased precipitation on growth of two ephemeral plants in the Gurbantunggut Desert, China

Ephemeral plants are a major component of biodiversity in the deserts of Northwest China, with important ecological functions. Information on plant morphological characteristics and biomass accumulation and allocation during different growth stages could enhance our understanding of the functional features and survival strategy of ephemeral plants. We examined the effects of increased precipitation on ephemeral species Eremopyrum distans and Nepeta micrantha in the Gurbantunggut Desert. Changes in morphological characteristics and biomass accumulation and allocation were analyzed under increasing precipitation 30% and 50% treatments. The results showed that increased precipitation 30% and 50% treatments promoted the growth of E. distans, with leaf area and reproductive organ biomass being increased by 14.2%-188.5% and 55.9%, respectively. The effects of increased precipitation on the growth of N. micrantha varied across different growth stages. At leaf expansion stage, increased precipitation promoted growth of N. micrantha, while at fruit ripening stage, increased precipitation 50% treatment reduced leaf area, plant height, and reproduction biomass by 54.9%, 20.5%, 43.2%, respectively. Thus, the responses of the two species to increased precipitation was species-specific. Increased precipitation would change the survival strategies of the two species, with consequence on the species composition and structure of desert community.

Plant Density Influences Reproductive Growth, Lint Yield and Boll Spatial Distribution of Cotton

The number of cotton plants grown per unit of ground area has gained attention due to the high prices of inputs and lower production. Cotton yield per unit of area in Henan province has been stagnant in the last few years. The objectives of this study were to investigate cotton growth, yield, boll spatial distribution and biomass accumulation using different plant densities at cultivation and to find out the optimal plant density. A 2-year field experiment was conducted in a randomized complete block design under six plant densities (D1, 15,000; D2, 33,000; D3, 51,000; D4, 69,000; D5, 87,000 and D6, 105,000 ha−1). Cotton grown at lower plant density produced taller plants and high number of leaves per plant while greater number of branches, fruiting nodes and high number of bolls per unit of ground area were produced under high plant density. Boll retention rate decreased as plant population increased and at nodes 1–8 the rate decreased slowly and then increased dramatically. The highest seed cotton yield (4546 kg ha−1) and lint yield (1682 kg ha−1) was produced by D5. The seed cotton and lint yield produced by D5 were 51–55%, 40–37%, 22–26%, 11–15%, 12–15%, 28–30%, 21–24%, 15–20%, 7–13% and 13–17% higher than D1, D2, D3, D4 and D6 during both years of experimentation, respectively. The increase in seed yield was due to higher biomass accumulation in reproductive organs under D5 plant density. The highest average (110.4 VA kg ha−1 d−1) and maximum (126 VM kg ha−1 d−1) rate of reproductive organs biomass was also accumulated by D5 as compared to other plant densities. The results suggest that D5 is the optimal plant density for high reproductive biomass accumulation and high yield for the area of Henan province.

Changes in vegetation composition and structure following livestock exclusion in a temperate fluvial wetland

AbstractQuestionsResponses of wetland systems to grazing can be highly variable with both positive or negative responses. However, the sustainable use of wetlands for grazing will depend on the management implemented and the resilience of each type of them. In this context, we addressed the question: will the vegetation in the studied wetland be able to recover its structural and functional parameters in the short term after livestock exclusion?LocationTemperate fluvial wetlands in the middle Delta of the Paraná River, Argentina, South America.MethodsWe evaluated the effect of cattle ranching on vegetation composition and diversity by determining changes in species richness and evenness, biomass (green and dry vegetative, and reproductive biomass), and litter content. We also analyzed the changes in biomass of weeds and of species according to their forage quality, toxicity, and growth form. We applied a randomized block design (by topographic position) with repeated measures over time, using livestock exclusion as treatment.ResultsAfter 16 months, livestock exclusion affected vegetation species richness, but did not have a significant effect on diversity due to a slightly compensatory effect of evenness. Species composition differed markedly among treatments over time. There was an increase in dry and green vegetative biomass and litter content after eight months of exclusion, while changes in reproductive biomass occurred later. The increase in these variables was closely related to changes in biomass of species with erect habit and good forage quality.ConclusionsLivestock exclusion increased the forage value for the studied wetland by the development of natural palatable species typical of these environments. This shift in species composition promoted a higher production in biomass in the ungrazed areas. This suggests a remarkable recovery of the structural and functional parameters of the vegetation communities in the short term (two years).

Mowing Frequency Influences Number of Flowering Stems but not Population Age Structure of Asclepias viridis, an Important Monarch Host Plant

Milkweeds (Asclepias spp.) are host plants for monarch butterflies (Danaus plexippus), which are currently being considered for listing under the Endangered Species Act. Previous research has documented declines in milkweed availability in the Midwest, but less research has focused on the southern Great Plains. Furthermore, the influence of management practices on the structure of milkweed populations has not been evaluated. We assess the age structure of Asclepias viridis, an important milkweed species for monarchs in the southern Great Plains, in two land uses that differ in the frequency and timing of mowing. Plant age may influence resource availability for larval and adult monarchs by affecting foliar biomass and flower production, and flower production and subsequent seed production may influence the recruitment of new individuals to the population. Using herb-chronology, we found age structure did not differ between roadsides mowed several times during the growing season and grasslands mowed less frequently. However, we did find younger individuals in less frequently mowed grasslands had more stems and more flowering stems than those in more frequently mowed roadsides. Though plant age did not differ among the land uses and mowing regimes included in this study, our results suggest frequent mowing can negatively affect foliar and reproductive biomass of younger A. viridis plants. Limiting mowing during the early summer flowering season for A. viridis could support efforts to maximize host plant and nectar availability for monarchs and other pollinators.

Self‐thinning and size‐dependent flowering of the grass Spartina alterniflora across space and time

Abstract Plants adjust their size and reproductive effort in response to numerous selection pressures and constraints. The self‐thinning law describes a well‐known trade‐off between size and density. Plants also trade‐off investment into growth vs. sexual reproduction, as described by life‐history theory. We build on past work on plant allometry and life history by examining both self‐thinning and size‐dependent reproduction in a single plant species, the saltmarsh grass Spartina alterniflora, across a wide range of settings: three landscape positions, two habitats and eight sites, across sixteen years. Plants in different landscape positions and years varied tremendously in size and shoot density. However, all this variation could be explained by a single allometric relationship consistent with the self‐thinning law, but with a lower slope. Flowering was size‐dependent, and the size at which plants had a 50% probability of flowering varied among habitat, sites and years. Plants that were stressed reproduced at a smaller size than plants that were growing under good conditions, and this pattern was consistent among habitat, sites and years. Finally, reproductive biomass and the proportion of shoots flowering increased with increasing vegetative size (plant height or shoot biomass). Combining these two patterns, S. alterniflora plants growing high density are small and reproduce at a smaller size than large plants growing at low density. Although there is tremendous spatial and temporal variation in S. alterniflora growth and reproductive patterns, all this variation can be understood as resulting from two simple allometric trade‐offs. Because saltmarsh plants often occur in monospecific stands, they may serve as simple, model systems for studies of plant life history. A free Plain Language Summary can be found within the Supporting Information of this article.

Effect of PPO-Inhibiting Herbicides on the Growth and Sex Ratio of a Dioecious Weed Species Amaranthus palmeri (Palmer Amaranth)

Amaranthus palmeri S. Watson (Palmer amaranth) is a fast-growing, dioecious, highly competitive agricultural weed species, which is spreading across the US Midwest. Population sex ratios are an important consideration in the management of A. palmeri populations as this species has become resistant to several herbicide sites of action, and there is need to minimize seed production by female plants. Environmental conditions, particularly stressors, may influence sex ratios, and herbicides act as major stressors and evolutionary filters in agricultural fields. Amaranthus spp. have shown a tendency for rapid evolution of herbicide resistance, with the frequency of protoporphyrinogen oxidase (PPO)-inhibitor resistance increasing across the Midwestern US. A greenhouse experiment was conducted to investigate the effect of two PPO-inhibiting herbicide treatments of either lactofen or fomesafen on four different Illinois populations (Cahokia, Collinsville, Rend Lake, and Massac). Plants raised from seed from the Massac population were tallest, and both males and females from this population also had the highest vegetative biomass. Female plants from the Collinsville population had more reproductive biomass than male plants. Control populations were male-biased (Cahokia, Collinsville), female-biased (Masaac), and 1:1 (Rend Lake). Lactofen shifted the male-biased populations to female-biased or 1:1 and the female-biased population to 1:1. Fomesafen-treated populations were male-biased or 1:1. This study suggests that PPO-inhibiting herbicide treatments may influence the growth and sex ratio of A. palmeri populations, which is an underlying factor in the rate of herbicide evolution in this species. An understanding of the underlying mechanisms of how external factors influence sex ratios may eventually provide an opportunity to reduce seed production in populations by shifting sex ratios towards a male bias.

Comparative response to drought in primitive and modern wheat: a cue on domestication.

Primitive wheat follows an opposite metabolic law from modern wheat with regard to leaf biomass/reproductive growth vs above-ground biomass that is under the regulation of non-hydraulic root signals and that influences resource acquisition and utilization. Non-hydraulic root signals (nHRS) are so far affirmed as a unique positive response to drying soil in wheat, and may imply huge differences in energy metabolism and source-sink relationships between primitive and modern wheat species. Using a pot-culture split-root technique to induce nHRS, four primitive wheat genotypes (two diploids and two tetraploids) and four modern wheat ones (released from different breeding decades) were compared to address the above issue. The nHRS was continuously induced in drying soil, ensuring the operation of energy metabolism under the influence of nHRS. We found that primitive wheat followed an opposite size-dependent allometric pattern (logy = αlogx + logβ) in comparison with modern wheat. The relationships between ear biomass (y-axis) vs above-ground biomass (x-axis), and between reproductive biomass (y-axis) and vegetative (x-axis) biomass fell into a typical allometric pattern in primitive wheat (α > 1), and the nHRS significantly increased α (P < 0.01). However, in modern wheat, they turned to be in an isometric pattern (α ≈ 1). Regardless of nHRS, either leaf (i.e., metabolic rate) or stem biomass generally exhibited an isometric relationship with above-ground biomass in primitive wheat (α ≈ 1), while in modern wheat they fell into an allometric pattern (α > 1). Allometric scaling of specific leaf area (SLA) or biomass density showed superior capabilities of resource acquisition and utilization in modern wheat over primitive ones. We therefore proposed a generalized model to reveal how modern wheat possesses the pronounced population yield advantage over primitive wheat, and its implications on wheat domestication.

Biomass and nitrogen distribution ratios reveal a reduced root investment in temperate lianas vs. self-supporting plants.

The reliance on external support by lianas has been hypothesized to imply a reduction in the biomass cost of stem construction and root anchorage, and an increased investment in leaves, relative to self-supporting plants. These evolutionary trade-offs have not been adequately tested in an ontogenetic context and on the whole-plant scale. Moreover, the hypothesis may be extended to other potentially limiting resources, such as nitrogen (N.). Plants belonging to five con-familiar pairs of temperate liana/shrub species were cultivated in 120 L barrels and sequentially harvested over up to three growing seasons. To account for the ontogenetic drift, organ biomass and nitrogen fractions were adjusted for plant biomass and N pool, respectively. Lianas invested, on average, relatively less biomass in the root fraction in comparison with shrubs. This was offset by only insignificant increases in leaf or stem investment. Even though liana stems and roots showed higher N concentration in comparison with shrubs, plant N distribution was mostly driven by, and largely matched, the pattern of biomass distribution. Lianas also showed a greater relative growth rate than shrubs. The differences between the growth forms became apparent only when ontogenetic drift was controlled for. These results were confirmed regardless of whether reproductive biomass was included in the analysis. Our results suggest that temperate lianas, in spite of their diverse, species-specific resource distribution patterns, preferentially allocate resources to above-ground organs at the expense of roots. By identifying this trade-off and demonstrating the lack of a general trend for reduction in stem investment in lianas, we significantly modify the prevailing view of liana allocation strategies and evolutionary advantages. Such a resource distribution pattern, along with the cheap unit leaf area and stem unit length construction, situates lianas as a group close to the fast acquisition/rapid growth end of the life strategy spectrum.

The relative contributions of functional diversity and functional identity to ecosystem function in water‐limited environments

AbstractQuestionsTwo central pathways have been proposed to dictate the relationship between community structure and ecosystem function: the “diversity effect” — trait variation allowing complementary resource use, and the “mass ratio effect” — ecosystem function determined overwhelmingly by the functional traits of the dominant species which shape the “functional identity”, i.e., community‐weighted mean trait values. However, the distinct effect of each pathway on ecosystem function is difficult to determine as they are complementary and shaped by environmental heterogeneity. We examined the distinct effects of functional diversity (FD) and identity (FI) on water consumption and use efficiency (WUE), vegetative and reproductive biomass production and reorganization capacity under variable water availability.MethodsEight semiarid annual plant species, varying in natural size range, were grown in different assemblages representing various levels of FD and FI. Assemblages were based on species potential growth rate (PGR) and grown under two water availability levels. We measured total biomass, seed biomass, root to shoot ratio and water consumption.ResultsFD had a distinct positive effect on water consumption, total biomass and seed production but not on WUE. Mean PGR (FI) had a distinct positive effect on water consumption and total biomass production, but a negative effect on WUE and seed production. FD and FI had no clear effects on reorganization capacity or stability in total biomass production in response to decreased water availability.ConclusionsWe present the discrete contributions of FD and FI to ecosystem function. The positive effect of FD on biomass production reflects better exploitation of the growing space and reduced competition through greater size diversity, emphasizing the importance of interplant interactions and differentiation for enhancing ecosystem function. The positive effect of FI on biomass production reflects the higher performance of high PGR species, albeit at the expense of WUE and seed production resulting from higher competition.

Differential responses of C3 and C4 grasses to shrub effects in a sub‐humid grassland of South America

AbstractQuestionsPlant–plant interactions are key processes that strongly affect the survival, growth and reproduction of individuals in plant communities. In grasslands, the micro‐environment generated under the canopy of shrubs could differentially affect co‐occurring species with different abiotic requirements. In a C3/C4 grassland with scattered shrubs, we asked the following questions: (a) Does the aerial effect, the below‐ground effect, and the net effect of shrubs affect the vegetative and reproductive biomass, the number of tillers, the biomass allocation, and the leaf elongation rate of grasses? and (b) Do these effects differ between C3 and C4 grasses?LocationTemperate sub‐humid grassland of Uruguay.MethodsWe planted one C3 and two C4 grasses under a shrub canopy and in adjacent open sites. Half of the grasses were planted with a fabric bag to reduce root competition with the shrub. We measured leaf elongation rate, the number of tillers produced and the biomass of the grasses in every treatment. We also measured photosynthetic photon flux density (PPFD), air temperature and wind speed under shrub canopies and in adjacent open sites.ResultsRoot biomass, aerial biomass and reproductive biomass, the number of tillers and the leaf elongation rate of the C4 grasses were negatively affected by the reduction in radiation and probably by below‐ground competition with the shrub. On the other hand, the leaf elongation rate of the C3 grasses was positively affected by the shrub canopy. PPFD, air temperature and wind speed were lower under shrubs than in adjacent open sites.ConclusionsOur results show the interplay between plant interactions and photosynthetic metabolism on the vegetative and reproductive performance of grasses. The micro‐environmental conditions generated below shrub canopies create a more appropriate site for the growth of C3 than for C4 grasses. These results show that shrubs may differentially affect co‐occurring species with different abiotic requirements.