Leaf Biomass Allocation Research Articles

Functional coordination between leaf traits and biomass allocation and growth of four herbaceous species in a newly established reservoir riparian ecosystem in China.

The flood‐dry‐flood cycle in the reservoir riparian zone (RRZ) of the Three Gorges Dam has dramatically altered the riparian ecosystem structure and composition. Previous field studies have shown that leaf traits varied greatly and were restricted to the lower‐investment and faster‐return end of the global leaf spectrum, which are typical characteristics of fast‐growing species. However, it is unclear as to the mechanism underpinning the growth potential of these species and how it will respond to soil nutrient availability and temperature. Here, we linked the plant functional traits of four representative dominant C4 herbaceous species (Setaria viridis, Echinochloa crusgalli, Cynodon dactylon and Hemarthria altissima) to their relative growth rates (RGR) under ambient and elevated temperatures, with different nitrogen and phosphorus levels, to explore the potential mechanism of species growth in the newly established reservoir riparian ecosystem in the Three Gorges Reservoir Area, China. We grew seedlings of these species in four open‐top chambers, with three levels of nutrient supplies under two temperature gradients (ambient temperature and an elevated temperature of 4°C). We found that the responses of the RGR and plant traits to soil N and P supply levels and temperature varied considerably among studied species. E. crusgalli displayed the lowest RGR associated with relatively low specific leaf area (SLA), leaf nitrogen content (LN), stem mass ratio (SMR), and high leaf mass ratio (LMR) and was less affected by soil N and P supply levels and temperature. C. dactylon and H. altissima showed the highest RGR compared to the other two species grown at the substrate of N = 0.4 mg/g, P = 0.2 mg/g at ambient air temperature, associated with a relatively high SMR, low LMR and low plant carbon content (PCC). However, the RGR advantage of the two species was diminished at elevated temperatures, while S. viridis showed the highest RGR compared to the other species. Across all datasets, the RGR had no association with the leaf area ratio (LAR) and SLA. The RGR also showed no significant relationships with the LN and leaf phosphorus content (LP). On the other hand, the RGR was captured adequately by the SMR, which can therefore be considered as a powerful functional marker of species’ functioning in this newly established reservoir riparian ecosystem. Our study provides some insight into the underlying mechanisms of species growth in reservoir riparian ecosystems.

Light spectral and thermal properties govern biomass allocation in tomato through morphological and physiological changes

We investigated the effects of light spectral and thermal properties on biomass allocation among vegetative and reproductive structures in tomato (Solanum lycopersicum L. ‘Merlice’) plants during growth and development and to determine its underlying mechanisms. Plants were grown in a greenhouse under a DLI of 3.4 mol m2 day−1 with/without supplemental lighting and a 16-h photoperiod, provided at equal photosynthetic photon flux density (PPFD of 230 μmol m‒2 s‒1 either from overhead high-pressure sodium (HPS) lamps or intracanopy light-emitting diode (LED) arrays: red light alone (R100; 100% of photosynthetically active radiation (%PAR)), red plus low far-red (R100+FR21), red plus high far-red (R100+FR41), and red plus blue (R61+B39). Supplemental lighting substantially increased total biomass and fruit yield, but to a greater extent by LED lighting regardless of spectrum. However, spectral contribution to leaf morphological traits and biomass allocation pattern varied greatly among the light treatments. HPS-supplemented plants had higher leaf temperature, photosynthetic rate (Pn), and transpiration rate (E) in the upper foliar canopy (161 to 240 cm from the base of the shoot) and contained higher water content in all tissues, particularly in roots by 2-fold, compared to LED-supplemented plants. They also had thinner, smaller leaves and allocated a higher fraction of total biomass to vegetative tissues, demonstrating their allocation strategies for effective transpiration and heat dissipation. Meanwhile, LED-supplemented plants allocated biomass preferentially to reproductive structures at the expense of vegetative tissues. Inclusion of higher FR or B with R light decreased leaf biomass fraction relative to total biomass but increased leaf dry mass and leaf thickness. Particularly, supplemental FR light significantly lowered the water content of leaves and fruits compared to B light. Long-term exposure of tomato plants to low R:FR was associated with reductions in leaf area, chlorophyll content, and vegetative shoot biomass fraction, increases in leaf thickness and fruit biomass, and acceleration of flowering and fruiting. Light-induced biomass allocation changed between vegetative and reproductive structures during plant growth and development. FR light had the most pronounced effect in this regard by significantly shifting dry-mass accumulation to fruits, via more efficient photosynthetic mechanisms and conserved water use. We conclude that light spectral and thermal properties affect biomass allocation among plant parts during tomato growth and development, and such responses involve morphological and physiological changes in tomato plants, ultimately affecting crop performance and yield.

Divergent responses to water and nitrogen addition of three perennial bunchgrass species from variously degraded typical steppe in Inner Mongolia

Water and nitrogen (N) availability to plants are spatially and temporally variable in arid and semi-arid grasslands. We aimed to investigate the eco-physiological responses of three bunchgrass species to water and N addition along a gradient of habitat degradation in the Inner Mongolian typical grasslands. The effects of water and N addition on aboveground and belowground growth and biomass allocation and water- and nitrogen-use efficiency (WUE and NUE) of Stipa grandis, Agropyron cristatum and Cleistogenes squarrosa from non-degraded, moderately-degraded and heavily-degraded grasslands, respectively, were compared. Stipa grandis had higher specific root length and WUE than C. squarrosa, while C. squarrosa had higher NUE than S. grandis in water- and N-limited conditions. Responses of A. cristatum were intermediate between those of S. grandis and C. squarrosa. Water and N addition did not have a significant effect on growth and biomass allocation of S. grandis, but it increased growth and leaf biomass allocation of A. cristatum and growth and stem biomass allocation of C. squarrosa. The three species differ in WUE, NUE, biomass allocation and responses to water and N addition, and these differences are adaptive to their respective habitats. The degraded grasslands can be restored by an increase in water and N availability such as is expected to occur via climatic change, but S. grandis will not benefit from the increases.

Blue light associated with low phytochrome activity can promote elongation growth as shade-avoidance response: A comparison with red light in four bedding plant species

To explore the action mode of blue light on elongation growth of bedding plants, the plant growth and morphology traits of petunia (Petunia × hybrida, ‘Duvet Red’), calibrachoa (Calibrachoa × hybrida, ‘Kabloom Deep Blue’), geranium (Pelargonium × hortorum, ‘Pinto Premium Salmon’), and marigold (Tagetes erecta, ‘Antigua Orange’) were compared under four light quality treatments: (1) R, “pure” red light (660 nm); (2) B, “pure” blue light (450 nm); (3) BR, “unpure” blue light created by mixing B with a low level of R to provide B/R ≈ 9; (4) BRF, “unpure” blue light created by adding a low level of far red light to BR with red/far red ≈ 1. Continuous (24-h) light-emitting diode lighting with either 100 or 50 μmol m−2 s−1 photosynthetic photon flux density at ≈ 23℃ was used with the above treatments. After 14–20 day of lighting treatment, B promoted elongation growth compared to R, as demonstrated by a greater canopy height, main stem length, internode length, and daily main stem extension rate. However, BR showed similar or inhibitory effects on these traits relative to R, while BRF exhibited similar promotion effects as B. The calculated phytochrome photoequilibrium, an indication of phytochrome activity, was higher for R (0.89) and BR (0.74) than for B (0.49) and BRF (0.63). Adding red (or far red) light reversed the effects of B (or BR) on elongation growth and the phytochrome photoequilibrium, suggesting that blue light promotion of elongation growth is related to the lower phytochrome activity. Also, B and BRF, when compared to R or BR, promoted elongation growth to a greater degree at 50 than 100 μmol m−2 s−1 for petunia and calibrachoa. In addition to the promoted elongation growth, B and BRF reduced side branch number, biomass allocation to side branches, leaf epinasty, leaf angle, and/or leaf chlorophyll content relative to R or BR, but increased individual leaf area, petiole length, and/or biomass allocation to main stem, which varied with different species. It suggests that the promoted elongation growth by blue light associated with lower phytochrome activity is one of shade-avoidance responses with varying sensitivity among species.

Improving Representation of Crop Growth and Yield in the Dynamic Land Ecosystem Model and Its Application to China

AbstractTo accurately assess the roles of agriculture in securing food security and maintaining environmental sustainability, it is essential to improve the representation of crop growth, development, and yield formation in global land models that traditionally focus on energy, water, carbon, and nitrogen exchanges between land and the atmosphere. In this study, a process‐based agricultural module has been coupled with the Dynamic Land Ecosystem Model (DLEM‐AG2.0) for assessing how multiple environmental factors (climate change, atmospheric CO2 concentration, tropospheric O3, and nitrogen deposition) and human activities (land use/cover change, nitrogen fertilizer use, and irrigation) have affected the crop growth, development, yield, carbon (C), nitrogen (N), and water cycles in agroecosystems. Here we describe the model structure for simulating crop growth, development, and yield formation in the DLEM‐AG2.0, and then we validate the model using field observations and a national yield survey for three major crops (wheat, maize, and rice) in China during 1980–2012. Results show that the DLEM‐AG2.0 is capable of simulating the dynamic processes of phenological development, leaf growth expansion, biomass accumulation, biomass allocation, and yield formation for wheat, maize, and rice with normalized root mean square errors of the simulations of less than 20%. Our model‐based yield estimation for the three major crops at the national scale for the period 1980–2012 is generally consistent with the national yield survey in China. The crop representation in the DLEM‐AG2.0 is flexible for extrapolating to a global scale after rigorous testing with both site‐specific and regional observations. Further advancement of agricultural modeling within the global land modeling framework will require consideration of human perception and behavior for adapting and mitigating global change.

Rising [CO2] changes competition relationships between native woody and alien herbaceous Cerrado species.

The structure of the Cerrado may be explained by the competition between woody and herbaceous species. However, the rising CO2 concentration ([CO2]) predicted under current climatic change may modify the ecophysiological responses of woody and herbaceous species owing to functional traits of each group, which may in turn modify vegetation structure as competitive relationships change among species. In this study we examined ecophysiological responses and competition between two cerrado species under elevated [CO2]. We selected an herbaceous alien grass (Melinis minutiflora P. Beauv.) and an endemic woody cerrado species (Hymenaea stigonocarpa Mart. ex Hayne). Hymenaea stigonocarpa individuals were maintained in three plots with different M. minutiflora densities: 0, 50 and 100% in two different [CO2] (380ppm and 700ppm) in open-top chambers. Leaf gas exchange, effective quantum efficiency of PSII, chlorophyll content, and growth increased in H. stigonocarpa plants under high [CO2]. The competition with M. minutiflora under elevated [CO2] led to an increase in specific leaf area, leaf area ratio and biomass allocation to shoots in H. stigonocarpa. In contrast, M. minutiflora had a delayed leaf development and high stem dry mass under elevated [CO2]. These changes in growth patterns under elevated [CO2] will modify allocation of resources, improving the competition potential of the woody species over the alien grass species in the Cerrado.

Early life conditions and precipitation influence the performance of widespread understorey herbs in variable light environments

Summary The understorey of tropical forests is heterogeneous across time, and plants that inhabit this layer may exhibit adaptations (e.g. trait plasticity) that enable them to exploit this variability to their advantage. We tested the hypothesis that two widespread understorey herbs would perform equally well in a variable as in a constant environment, using a 2‐year shade‐house experiment. We measured demographic traits (growth and survival), a physiological trait (maximum photosynthetic capacity), and life‐history traits (leaf life span and biomass allocation) of Heliconia tortuosa and Calathea crotalifera. We investigated how these traits were affected by light availability at the seedling stage, precipitation, and whether individuals experienced a constant or variable light environment. Whether or not a variable environment was favourable for plants depended upon precipitation and the environment in which individuals started life. At low precipitation, plants in a variable light environment grew more than those in a constant environment, but only when individuals had lived as seedlings in low light. At high precipitation, plants in a constant environment grew more than those in a variable environment, regardless of early conditions. Survival was lower in a variable environment at low precipitation, and more so at high precipitation. Photosynthetic capacity was lower for individuals in a variable environment than in a constant environment when they had lived in high light as seedlings. Calathea grew faster and survived more poorly than Heliconia, independently of the treatments. Calathea grew more at high than low precipitation while Heliconia grew more at low than high precipitation. Leaf life span and biomass allocation did not differ among treatments, although Calathea had a significantly greater proportion of its biomass above‐ground vs. that of Heliconia. Synthesis. Environmental variability had a neutral or positive effect on biomass allocation, photosynthetic capacity, and leaf life span for these species. Survival was the only trait that was always lower in a variable environment. The effect of environmental variability was dependent on early life conditions as well as precipitation, suggesting that generalist species may experience high fitness as forest environments become more variable by maintaining high growth at the expense of survival.

A morphophysiological analysis of the effects of drought and shade on Catalpa bungei plantlets

The interactive effects of shade and drought on the morphological and physiological traits of Catalpa bungei plantlets were assessed. Seedling growth, biomass, biomass allocation, leaf morphology, chlorophyll (Chl) content and gas-exchange parameters were measured in plants raised for 3 months under three light levels [80% (HI), 50% (MI), 30% (LI)] and two water levels [moisture (M) and drought (D)]. The results showed that shade greatly decreased growth, biomass, leaf area (LA) and Chl a/b; increased specific leaf area (SLA) and Chl content; and reduced photosynthetic rate (P n). Drought reduced the growth, biomass, LA, SLA, Chl a/b, P n, stomatal conductance (G s), transpiration rate (T r) and intercellular carbon dioxide concentration (C i) and increased the Chl content. Stomatal closure was an early physiological response to water stress. Light, water and their interaction significantly affected plant traits and their bivariate relationships. The phenotypic plasticity index of light (0.47) was much higher than that of water (0.21), indicating that light was the main driver of the variations observed. Under drought stress, growth, biomass, leaf and stem biomass allocation significantly decreased in the HI and MI environments, whereas no significant difference was observed in growth or biomass parameters under the LI condition. Furthermore, no significant difference was observed in P n, G s, or T r under the LI condition under water stress. Our results showed that shade did not alter the negative effects caused by drought stress in MI but did alleviate the negative effects of the LI condition. In summary, the effect of drought on C. bungei plantlets depends on the irradiance conditions.

Management of Cleome rutidosperma DC. using high crop density in dry-seeded rice

Cleome rutidosperma is one of the invasive C3 weed species in dry-seeded rice systems in South and Southeast Asia. Cleome species have shown a cytological developmental progression from C3 to C4 photosynthesis. Hence, a better understanding of growth responses of the weed in rice is critical in developing sustainable integrated management approaches for the suppression of this weed. Physiological and morphological changes of C. rutidosperma were studied in a pot experiment by growing the weed alone (1 plant per pot; 0.045 m2) and in competition with 4, 8, 12, and 16 plants per pot of two rice cultivars namely, IR64 and SACG4, in separate pots. The plant height of C. rutidosperma was not affected by the rice density or cultivar, and the height increased linearly with increasing time. The leaf area production of the lower half of the weed was reduced by 80–88% when grown with 12 and 16 rice plants compared to that grown without rice interference. Rice interference at the density of 16 plants per pot reduced leaf biomass of the weed by 92%, inflorescence biomass by 93%, stems biomass by 90%, and root biomass by 92% compared to the weed plants grown alone. The leaf and stem biomass allocation was higher to the lower half of the weed than that to the upper half, when grown in competition with rice. The specific stem length of C. rutidosperma increased by 84% in the presence of 12 rice plants (sowing density 60 kg/ha) compared to 4 plants (sowing density 20 kg/ha), indicating the change in resource allocation to stem elongation to enable the weed to compete effectively under shade to acquire light. However, the relative growth rate of the weed declined by 28% and 54% in the presence of 16 rice plants (sowing density of 80 kg/ha) during 3–5 and 5–7 weeks after sowing, respectively, compared to when the weed was grown without rice interference, reflecting less competitiveness of the weed for the resource acquisition under crop competition. The results of this study showed that the rice interference alone can reduce the weed's growth to a great extent. Therefore, the need of integration of other management practices in dry-seeded rice along with crop interference is highlighted to achieve complete control of C. rutidosperma and similar weeds.

<b>Influence of light on the initial growth of invasive <i>Cryptostegia madagascariensis</i> Bojer in the Brazilian semiarid region

The invasion by Cryptostegia madagascariensis causes economic and environmental problems in Northeastern Brazil. Current study evaluates the initial growth of C. madagascariensis on light gradient. The experiment used 0, 30, 50 and 70% shading treatments arranged in a completely randomized design and evaluated in four periods, namely, 35, 50, 65 and 80 days. Height, absolute growth rate, relative growth rate, number of side branches, number of leaves, leaf area, specific leaf area, leaf area ratio, root mass ratio, stem mass ratio, leaf mass ratio and leaf area/root mass ratio were evaluated. Results showed that the height was greater in shade environments, and the greater the available light, the greater was the number of side branches. C. madagascariensis is able to change the leaf area, specific leaf area and biomass allocation in different shadings. Since C. madagascariensis varies growth forms and performs morphological adjustments to increase light uptake, the plant has warranted success during the initial growth under different shadings.

Biomass allocation and organs growth of cucumber (Cucumis sativus L.) under elevated CO2 and different N supply

This article studied the effects of nitrogen (N) and CO2 enrichment on biomass and N accumulation and partitioning of cucumber grown in open top chambers. At the seedling stage, elevated CO2 increased the biomass and N content of the entire plant. The root had the largest increase in biomass and N content among the organs and more biomass allocation. The largest drops of N concentration showed in root at moderate and high N, in leaf at low N, respectively. Elevated CO2 increased stem biomass allocation at moderate and high N, but decreased leaf biomass allocation at all N levels. At the initial fruit stage, the response to elevated CO2 of biomass and N content decreased. Elevated CO2 increased biomass allocation to leaf and resulted in the largest drop of leaf N concentration at low and moderate N supply. High N supply promoted biomass production and N reallocation from the leaf to fruit, but decreased leaf biomass allocation. Thus, biomass allocation is initially affected by root–shoot growth balance to adapt to enriched CO2, leading to the largest root growth, then biomass allocates to another sink (stem). Long exposure of elevated CO2 results in photosynthetic acclimation in deficient N supply, which probably attributes to excessive stem and leaf biomass allocation and shortage of fruit storage. But high N shifts biomass allocation from leaf to fruit. Practically, sufficient N supply is needed for an efficient transport of carbohydrates to fruits and increases the yields under elevated CO2.

Typha domingensis Pers. growth responses to leaf anatomy and photosynthesis as influenced by phosphorus

Cattail (Typha domingensis Pers.) can show intense growth depending on phosphorus (P) eutrophication. We verify how P enrichment and deficiency influence T. domingensis growth and the relationship with anatomical and physiological modifications. Vegetative T. domingensis plants were grown for 60 days in a modified nutrient solution in five P levels: 0, 0.20, 0.40, 0.60 and 0.80mM. Plant growth was evaluated at the end of the experiment. Leaf fragments were collected and fixed in F.A.A.70 and sectioned in bench-top microtome. Sections were stained with safrablau solution, mounted in slides and photographed with an optical microscope. Images were evaluated in UTHSCSA-Imagetool software which was used to measure leaf tissues. Leaf gas exchanges were evaluated 30 and 60 days after the experiment started. The data were submitted to one-way ANOVA and regression analyses or means were compared using the Scott–Knott test. Plants showed more growth in a P-rich nutrient solution. T. domingensis showed different biomass partitioning under P levels, with an increasing leaf biomass allocation for higher P levels and a lower rhizome investment. For higher P levels, plants showed increased photosynthesis, stomatal conductances and transpiratory rates. However, the highest concentration promoted a decrease in these characteristics. The leaves of T. domingensis showed larger stomata, thicker palisade parenchyma and an increased phloem proportion under higher P levels. Our results suggest that the increased growth of T. domingensis in P-rich conditions may be related to increased photosynthesis; this characteristic is limited to anatomical traits such as palisade parenchyma and stomatal modifications.

Leaf physiology and biomass allocation of backcross hybrid American chestnut (Castanea dentata) seedlings in response to light and water availability.

Partial canopy cover promotes regeneration of many temperate forest trees, but the consequences of shading on seedling drought resistance are unclear. Reintroduction of blight-resistant American chestnut (Castanea dentata (Marsh.) Borkh.) into eastern North American forests will often occur on water-limited sites and under partial canopy cover. We measured leaf pre-dawn water potential (Ψpd), leaf gas exchange, and growth and biomass allocation of backcross hybrid American chestnut seedlings from three orchard sources grown under different light intensities (76, 26 and 8% full photosynthetically active radiation (PAR)) and subjected to well-watered or mid-season water-stressed conditions. Seedlings in the water-stress treatment were returned to well-watered conditions after wilting to examine recovery. Seedlings growing under medium- and high-light conditions wilted at lower leaf Ψpd than low-light seedlings. Recovery of net photosynthesis (Anet) and stomatal conductance (gs) was greater in low and medium light than in high light. Seed source did not affect the response to water stress or light level in most cases. Between 26 and 8% full PAR, light became limiting to the extent that the effects of water stress had no impact on some growth and morphological traits. We conclude that positive and negative aspects of shading on seedling drought tolerance and recovery are not mutually exclusive. Partial shade may help American chestnut tolerate drought during early establishment through effects on physiological conditioning.

Early responses to cadmium of two poplar clones that differ in stress tolerance

Soil cadmium (Cd) contamination is becoming a matter of great global concern. The identification of plants differentially sensitive to Cd excess is of interest for the selection of genotype adaptive to grow and develop in polluted areas and capable of ameliorating or reducing the negative environmental effects of this toxic metal. The two poplar clones I-214 (Populus×canadensis) and Eridano (Populus deltoides×maximowiczii) are, respectively, tolerant and sensitive to ozone (O3) exposure. Because stress tolerance is mediated by an array of overlapping defence mechanisms, we tested the hypothesis that these two clones differently sensitive to O3 stress factor also exhibit different tolerance to Cd. With this purpose, an outdoor pot experiment was designed to study the responses of I-214 and Eridano to the distribution of different Cd solutions enriched with CdCl2 (0, 50 and 150μM) for 35 days. Changes in leaf area, biomass allocation and Cd uptake, photosynthesis, chlorophyll fluorescence, leaf concentration of nutrients and pigments, hydrogen peroxide (H2O2) and nitric oxide (NO) production and thiol compounds were investigated. The two poplar clones showed similar sensitivity to excess Cd in terms of biomass production, photosynthesis activity and Cd accumulation, though physiological and biochemical traits revealed different defence strategies. In particular, Eridano maintained in any Cd treatment the number of its constitutively wider blade leaves, while the number of I-214 leaves (with lower size) was reduced. H2O2 increased 4.5- and 13-fold in I-214 leaves after the lowest (L) and highest (H) Cd treatments, respectively, revealing the induction of oxidative burst. NO, constitutively higher in I-214 than Eridano, progressively increased in both clones with the enhancement of Cd concentration in the substrate. I-214 showed a more elevated antioxidative capacity (GSH/GSSG) and higher photochemical efficiency of PSII (Fv/Fm) and de-epoxidation degree of xantophylls-cycle (DEPS). The glutathione pool was not affected by Cd treatment in both clones, while non-protein thiols and phytochelatins were reduced at L Cd treatment in I-214. Overall, these two clones presented high adaptability to Cd stress and are both suitable to develop and growth in environments contaminated with this metal, thus being promising for their potential use in phytoremediation programmes.

Interactive Effects of Increased UV-B and Rainfall on Growth and Physiology of Tibet Barley on the Tibetan Plateau

UV-B radiation and rainfall have tended to increase over the past decades in the Tibetan Plateau. A controlled field experiment, which simulated a 5% and 10% increase in UV-B radiation and a 10% and 20% increase in rainfall, was conducted to address the effects of enhanced UV-B radiation and increased rainfall on the leaf water potential, gas exchange, growth and biomass allocation, and phenology of Tibetan barley (Hordeum vulgare var. trifurcatum). Enhanced UV-B radiation conferred significant effects on the net photosynthetic rate (Pn), transpiration (E), stomatal conductance (gs), water use efficiency (WUE), total biomass, and spike length; the increased rainfall only affected Pn, E, and gs. These findings indicated that enhanced UV-B radiation had a more profound impact on the physiological and growth traits than the increased rainfall. Significant interactions of enhanced UV-B radiation and increased rainfall were also observed on leaf water potential, Pn, E, gs, WUE, total biomass, spike length, and relative growth rate. The leaf water potential was significantly increased with enhanced UV-B under the condition of a 20% increase in rainfall, Pn and biomass accumulation were also increased with enhanced UV-B under the conditions of increased rainfall, and the phenological stages were also delayed under ambient rainfall, but, this phenomenon disappeared gradually with an increased rainfall. It was therefore inferred that increased rainfall was able to offset the adverse impacts of enhanced UV-B radiation.

Linking relative growth rates to biomass allocation: the responses of the grass Leymus chinensis to nitrogen addition

Relative growth rate (RGR) of plants is a key component of fitness. Theoretically, the RGR of plants would be closely related with biomass allocation. Our mechanistic understanding of the relationship between RGR and biomass allocation under global change scenarios is still limited. We examined the responses of RGR and biomass allocation of Leymus chinensis, a dominant grass in the temperate steppe of northern China, to a wide range of N addition. We found that N addition increased RGR of L. chinensis up to a threshold of 10 g N/m2. While leaf and stem weight ratios were positively correlated with N addition rates, root weight ratio showed a negative correlation. The RGR of total biomass was positively correlated with both leaf and stem weight ratios, but negatively correlated with root weight ratios. The positive responses of leaf and stem biomass allocation, or the negative responses of root biomass allocation to N addition determined enhancements or reductions, respectively, of RGR on L. chinensis. The increased RGR of L. chinensis to N addition gave a direct and robust explanation for the increased of dominance of this species under field N-addition studies. Our results have important implications for projecting the growth status of L. chinensis under scenarios of increased N deposition in northern China.

Adaptation of biomass allocation patterns of wild Fritillaria unibracteata to alpine environ-ment in the eastern Qinghai-Xizang Plateau

Aims Under different selection stresses, alpine plants tend to adjust their biomass investments to different functions and/or organs, and this biomass allocation strategy presents different patterns during different life history stages of plants. Our objective is to address three hypotheses regarding Fritillaria unibracteata: 1) elevation gradients impact individual bulb biomass and individual total biomass; 2) biomass allocation adapts to the elevational change of environmental factors; and 3) biomass allocation at different life history stages show different patterns. Methods We collected wild F. unibracteata at different elevations in the alpine belt of Songpan County in the eastern Tibetan Plateau. The samples were cleaned and divided into different organs, the biomasses of which were then weighed after being dried in the oven. Important finding Elevation significantly affected individual bulb biomass (IBB) and individual total biomass (ITB), both of which decreased gradually with increased elevation. Elevation representing the heat factor was the pivotal factor limiting the growth of alpine plants such as F. unibracteata. For plants with different life history stages, their biomass allocation presented diverse patterns. First, the bulb biomass allocation (BBA) of 2-year-old F. unibracteata significantly decreased with increased elevation, but its leaf biomass allocation (LBA) increased. Second, both BBA and LBA of 3-and 4-year-old F. unibracteata were relatively stable at different elevations, but their stem biomass allocation (SBA) significantly decreased with increased elevation. In contrast, the sexual reproductive (flower) allocation (SRA) significantly increased with increased elevation. Third, at different life history stages, the root biomass allocation (RBA) of F. unibracteata was relatively stable at different elevations. Both RBA and SBA showed an increasing trend with the growth of plants, but BBA and LBA showed a decreasing trend.Three-year-old individuals normally had the maximum IBB.

Effects of elevated CO2, warming and precipitation change on plant growth, photosynthesis and peroxidation in dominant species from North China grassland

Warming, watering and elevated atmospheric CO₂-concentration effects have been extensively studied separately; however, their combined impact on plants is not well understood. In the current research, we examined plant growth and physiological responses of three dominant species from the Eurasian Steppe with different functional traits to a combination of elevated CO₂, high temperature, and four simulated precipitation patterns. Elevated CO₂ stimulated plant growth by 10.8-41.7 % for a C₃ leguminous shrub, Caragana microphylla, and by 33.2-52.3 % for a C₃ grass, Stipa grandis, across all temperature and watering treatments. Elevated CO₂, however, did not affect plant biomass of a C₄ grass, Cleistogenes squarrosa, under normal or increased precipitation, whereas a 20.0-69.7 % stimulation of growth occurred with elevated CO₂ under drought conditions. Plant growth was enhanced in the C₃ shrub and the C₄ grass by warming under normal precipitation, but declined drastically with severe drought. The effects of elevated CO₂ on leaf traits, biomass allocation and photosynthetic potential were remarkably species-dependent. Suppression of photosynthetic activity, and enhancement of cell peroxidation by a combination of warming and severe drought, were partly alleviated by elevated CO₂. The relationships between plant functional traits and physiological activities and their responses to climate change were discussed. The present results suggested that the response to CO₂ enrichment may strongly depend on the response of specific species under varying patterns of precipitation, with or without warming, highlighting that individual species and multifactor dependencies must be considered in a projection of terrestrial ecosystem response to climatic change.

Mutual Effects of Rottboellia cochinchinensis and Maize Grown Together at Different Densities

A greenhouse experiment was performed to test whether competition, and possibly allelopathy, were involved in Rottboellia cochinchinensis–maize interactions in two soil conditions: fertilized and unfertilized. Changes in morphological and physiological growth parameters for each species were determined by classical plant growth analysis. The dry weight and total leaf area of maize grown with Rottboellia decreased significantly as the density of the weed or maize plants increased, particularly under unfertilized conditions. At high densities of Rottboellia, regardless of fertilization, its root biomass allocation was 38% greater than the stem and leaf biomass allocation. In contrast, in unfertilized conditions, Rottboellia biomass allocation was higher in leaves than in roots and stems at high densities of maize or Rottboellia. Relative crowding coefficient values indicated that maize had a competitive advantage over Rottboellia. Mutual allelopathic effects of maize–Rottboellia interactions were not fully demonstrated because plant relative yield values were not significant among treatments. When the density of Rottboellia increased, its total leaf area and total dry weight significantly decreased, greater than when the density of maize increased. These results indicate that intra‐specific competition between Rottboellia plants was greater than inter‐specific competition with maize. High densities of maize significantly reduced the total leaf area of maize and Rottboellia. Reductions in the total leaf area of maize were greater under unfertilized conditions. The results showed that maize was more affected by fertilization than by the density of plants.

Effects of biochars produced from different feedstocks on soil properties and sunflower growth

AbstractThe use of biochar as a soil amendment is gaining interest to mitigate climate change and improve soil fertility and crop productivity. However, studies to date show a great variability in the results depending on raw materials and pyrolysis conditions, soil characteristics, and plant species. In this study, we evaluated the effects of biochars produced from five agricultural and forestry wastes on the properties of an organic‐C‐poor, slightly acidic, and loamy sand soil and on sunflower (Helianthus annuus L.) growth.The addition of biochar, especially at high application rates, decreased soil bulk density and increased soil field capacity, which should impact positively on plant growth and water economy. Furthermore, biochar addition to soil increased dissolved organic C (wheat‐straw and olive‐tree‐pruning biochars), available P (wheat‐straw biochar), and seed germination, and decreased soil nitrate concentration in all cases. The effects of biochar addition on plant dry biomass were greatly dependent upon the biochar‐application rate and biochar type, mainly associated to its nutrient content due to the low fertility of the soil used. As a result, the addition of ash‐rich biochars (produced from wheat straw and olive‐tree pruning) increased total plant dry biomass. On the other hand, the addition of biochar increased the leaf biomass allocation and decreased the stem biomass allocation. Therefore, biochar can improve soil properties and increase crop production with a consequent benefit to agriculture. However, the use of biochar as an amendment to agricultural soils should take into account its high heterogeneity, particularly in terms of nutrient availability.