Aboveground Vegetative Growth Research Articles

Seasonal coordination of aboveground vegetative and reproductive growth and storage in apple trees subjected to defoliation, flower and fruit thinning

Key messageThe growth rates of current-year shoots, fruits and trunks in apple trees peak sequentially during the growing season. The period of most intense growth coincided with the lowest NSC reserves.Vegetative and reproductive growth and storage are major carbon sinks in fruit trees; however, little is known about their mutual seasonal coordination. In this study, we monitored growth dynamics of trunks, fruits and current-year shoots together with the concentration of non-structural carbohydrates (NSC) in trees subjected to defoliation, early season flower thinning, mid-season fruit thinning and their respective combinations across the season. We found that defoliation had a negative effect on both trunk radial growth and annual fruit yield. Flower and fruit thinning caused lower fruit number per tree, but the individual fruits were larger resulting in a similar annual fruit yield among the treatments. Shoot extension growth was not significantly affected by the defoliation and flower and fruit thinning treatments. The concentration of non-structural carbohydrates was also similar across treatments. Modelled daily growth rates of shoots, fruits and trunks peaked sequentially one after another throughout the growing season with a delay of 15 and 18 days, respectively. The period of most intense growth of tree’s organs corresponded well with the lowest NSC reserves and a temporary depletion of starch in 1-year-old branches. Taken together, our study illustrates a tight temporal coordination of major carbon sinks and improves our understanding of sink/source relations of commercially important apple trees.

Impacts of reduced water availability on vegetative and reproductive traits of a Solanum species

AbstractWhile drought is known to affect crop yields negatively, there is limited knowledge of the strategies used by animal‐pollinated plants to cope with such conditions. In this study, we simulated low and moderate drought conditions in a greenhouse experiment and examined the vegetative and reproductive traits of a buzz‐pollinated species (Solanum lycopersicum). Our findings indicate that individuals exposed to both drought conditions decreased in height and bore fewer leaves but increased in the ratio of root length to dry mass. The number of flowers produced per day and the overall flower production were higher in plants under control conditions. We found no differences in the onset of flowering between the treatments, but the plants exposed to low drought showed peak flowering earlier. Among the morphometric traits, flower height, floral diameter, petal length, and petal width were significantly lower in both drought conditions. Individuals in the moderate‐drought treatment displayed greater variation in reproductive traits than those in the low‐drought treatment. Overall, drought stress negatively impacted the aboveground vegetative growth and the reproductive efforts of plants.

Tissue-Specific Transcriptomes in the Secondary Cell Wall Provide an Understanding of Stem Growth Enhancement in Solidago canadensis during Invasion.

Invasive plants generally present a significant enhancement in aboveground vegetative growth, which is mainly caused by variation in secondary cell wall (SCW) deposition and vascular tissue development. However, the coordination of the transcriptional regulators of SCW biosynthesis is complex, and a comprehensive regulation map has not yet been clarified at a transcriptional level to explain the invasive mechanism of S. canadensis. Here, RNA sequencing was performed in the phloem and xylem of two typical native (US01) and invasive (CN25) S. canadensis populations with different stem morphologies. A total of 296.14 million high-quality clean reads were generated; 438,605 transcripts and 156,968 unigenes were assembled; and 66,648 and 19,510 differential expression genes (DEGs) were identified in the phloem and xylem, respectively. Bioinformatics analysis indicated that the SCW transcriptional network was dramatically altered during the successful invasion of S.canadensis. Based on a comprehensive analysis of SCW deposition gene expression profiles, we revealed that the invasive population is dedicated to synthesizing cellulose and reducing lignification, leading to an SCW with high cellulose content and low lignin content. A hypothesis thus has been proposed to explain the enhanced stem growth of S. canadensis through the modification of the SCW composition.

Do different vegetative organs exhibit a similar temperature sensitivity in growth?

Although phenology and growth traits of leaves or woods have been the focus of research on growth-climate relationships, more is needed regarding whether there is a consistent growth response of different organs to environmental change. However, such work is crucial to accurately assess the impact of climate change on tree growth. Here, the growth timing, duration, rate, and increment of Picea meyeri needles, shoots, and stems were examined, and the corresponding environmental effects were revealed along an altitudinal gradient (2040–2740 m a.s.l.) in North-Central China during 2016 and 2017. The three organs showed a consistent altitudinal variation in growth onset timing, but a different variation in other traits; the growth duration, rate, and increment of needles changed slightly while those of shoots and stems dropped markedly with altitude. The air temperature was the key environmental factor driving the altitudinal variation. For each 1 °C increase in air temperature, the onset timing of needle and shoot elongation and xylem cell production was synchronously advanced by 3.3–3.7 ± 0.2 days; the peak timing was advanced by 3.4 ± 0.2 days, 2.2 ± 0.1 days, and 0 days; and the cessation timing was delayed by −3.8 ± 0.0 days, 2.1 ± 0.3 days, and 2.4 ± 0.1 days. Meanwhile, the duration was lengthened by 0 days, 5.6 ± 0.3 days, and 6.4 ± 0.2 days, respectively; the average rate was improved by 0%, 7.0 ± 1.2%, and 6.5 ± 0.5%, respectively; the increment was increased by 1.3 ± 0.1%, 8.2 ± 0.4%, and 11.0 ± 0.4%, respectively. These findings suggested that the aboveground vegetative growth of P. meyeri exhibits different temperature sensitivities; stem growth will benefit more from future warming than shoot and needle growth. It adds a new clue to conducting growth-climate relationship studies, and the response difference of organ growth to temperature should be considered in revealing future climate warming on tree growth.

GbLMI1 over-expression improves cotton aboveground vegetative growth

Leaves are the main organ for photosynthesis and organic synthesis in cotton. Leaf shape has important effects on photosynthetic efficiency and canopy formation, thereby affecting cotton yield. Previous studies have shown that LMI1 (LATE MERISTEM IDENTITY1) is the main gene regulating leaf shape. In this study, the LMI1 gene was inserted into the 35S promoter expression vector, and cotton plants overexpressing LMI1 (OE) were obtained through genetic transformation. Statistical analysis of the biological traits of the T1 and T2 populations showed that compared to the wild type (WT), OE plants had significantly larger leaves, thicker stems and significantly greater dry weight. Furthermore, plant sections of the main vein and petiole showed that the numbers of cells in those tissues of OE plants were significantly greater. In addition, RNA-seq analysis revealed the differential expression of genes related to gibberellin synthesis and NAC gene family (genes containing the NAC domain) between the OE and WT plants, suggesting that LMI1 is involved in secondary wall formation and cell proliferation, which promotes stem thickening. Moreover, Gene Ontology (GO) analysis revealed enrichment in the terms of calcium ion binding, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed enrichment in the terms of fatty acid degradation, phosphatidylinositol signal transduction system, and cAMP (cyclic adenosine monophosphate) signal pathway. These results suggested that LMI1 OE plants are responsive to gibberellin hormone signals, and have altered messenger signals (cAMP, Ca2+) which amplify this function, to promote stronger aboveground vegetative growth. This study found the LMI1 greatly increased the vegetative growth in cotton, which is the basic requirement for higher yield.

Does a tragedy of the commons due to individual competition arise from genetically fixed traits or plastic traits in dryland wheat? An experimental verification

Abstract Growth redundancy, the overgrowth of resource-foraging organs in crop stands, is often detrimental to yield and is thus called a ‘tragedy of the commons’. A tragedy can also arise owing to the plastic overproduction of competitive structures when intra-variety individuals forage in close proximity to each other. However, little is known about the sensitivity of crop varieties and resource availability to this ‘plastic’ tragedy. Pot experiments were designed to investigate this issue. The root competition environment was imposed by growing two plants of the same variety in mesh and plastic partitions. Two wheat varieties (old Monkhead and modern 92-46) were used, and two resource levels were established. Compared with 92-46, Monkhead allocated more biomass to stems and leaves and concurrently less to seeds. We identified intra-variety neighbour effects only in 4 out of 24 allometric comparisons with a small magnitude. Allometric data also revealed a lowered response to fertilizer addition in 92-46 than in Monkhead. Based on a limited sample size, our results revealed a trade-off between above-ground vegetative growth and crop yield. This trade-off resulted in a tragedy of the commons in old Monkhead and enhanced yields in modern 92-46. The tragedy of the commons in wheat may generally arise from genetically fixed traits in terms of growth redundancy in old varieties, rather than from the plastic behaviour of individuals. Modern 92-46 may adopt a conservative strategy of resource use, whereas old Monkhead employs an exploitative strategy. Our findings highlight breeders should select genotypes with low individual competitiveness.

A dinitroaniline herbicide resistance mutation can be nearly lethal to plants.

Lolium rigidum is the most important weed in Australian agriculture and pre-emergence dinitroaniline herbicides (e.g., trifluralin) are widely and persistently used for Lolium control. Consequently, evolution of resistance to dinitroaniline herbicides has been increasingly reported. Resistance-endowing target-site α-tubulin gene mutations are identified with varying frequency. This study investigated the putative fitness cost associated with the common resistance mutation Val-202-Phe and the rare resistance mutation Arg-243-Met causing helical plant growth. Results showed a deleterious effect of Arg-243-Met on fitness when plants are homozygous for this mutation. This was evidenced as high plant mortality, severely diminished root and aboveground vegetative growth (lower relative growth rate), and very poor fecundity compared with the wild-type, which led to a nearly lethal fitness cost of >99.9% in competition with a wheat crop. A fitness penalty in vegetative growth was evident, but to a much lesser extent, in plants heterozygous for the Arg-243-Met mutation. By contrast, plants possessing the Val-202-Phe mutation exhibited a fitness advantage in vegetative and reproductive growth. The α-tubulin mutations Arg-243-Met and Val-202-Phe have contrasting effects on fitness. These results help understand the absence of plants homozygous for the Arg-243-Met mutation and the high frequency of plants carrying the Val-202-Phe mutation in dinitroaniline-resistant L. rigidum populations. The α-tubulin Arg-243-Met mutation can have an exceptional fitness cost with nearly lethal effects on resistant L. rigidum plants. © 2022 Society of Chemical Industry.

Multifunctions of fine root phenology in vegetative and reproductive growth in mature beech forest ecosystems

AbstractMasting, a large interannual variation of reproductive investment spatially synchronized within perennial plants, is an important factor for understanding the use and storage of carbon and nutrient resources in various forest ecosystems. Fine roots play essential roles in water and nutrient uptake but also consume a large amount of net primary production (NPP) during growth. Understanding masting mechanisms requires knowledge of how masting trees succeed in abundant fructification by adjusting resource acquisition via fine roots and how mast seeding influences fine root dynamics. The aims of the present study were to estimate interannual variations in NPP, including belowground production, over several years while evaluating fine root phenology and to suggest possible relationships between fine root growth and the production of nuts, leaves, and woody biomass in mature forest ecosystems. Nut and leaf production was quantified using litter traps in two beech forests located at different altitudes of 550 and 1500 m, and woody biomass increment was estimated using allometric equations. Seasonal and mass‐based annual fine root production was determined using minirhizotrons and soil cores. Correlations between seasonal fine root and aboveground production were analyzed using the state‐space model, which can verify masting effects on fine root production between flower bud formation and mast seeding. NPP estimates exhibited almost biennial or irregular masting behavior. Nut production was positively correlated with fine root production in autumn of the previous year in the lower site but showed negative correlations with that in the early growing season of the same year in the upper site. The former indicated enhanced fine root production to absorb nutrients prior to mast seeding, and the latter suggested the suppression of fine root production due to resource depletion during masting. Fine root production increased with increasing leaf production in the early growing season in both sites, indicating the corresponding water transport between them. Thus, fine root phenology has distinct multiple functions to ensure water and nutrient resources in supporting aboveground vegetative and reproductive growth, resulting in variable seasonal patterns of fine root production.

Assessing the nitrogen status of almond trees by visible-to-shortwave infrared reflectance spectroscopy of carbohydrates

Precise nitrogen (N) fertilization requires new indices of plants’ nutritional status. Non-structural carbohydrates (NSC) are the energetic currency of plants and can, thus, serve as a physiological indicator for their condition. Nevertheless, only a few records exist about NSC composition and allocation in crops, and their relationship with N uptake and the current methods to detect NSC compositions in plants are cumbersome and expensive, which limits their use. The current work aimed to associate the nutritional status of almond trees with the carbohydrate compositions in their roots, branches, and leaves by a high-throughput technique. We found that low N availability forces trees to allocate carbohydrates to their roots. High N availability, on the other hand, promoted above-ground vegetative growth, and minimized carbohydrate storage in the leaves. These observations implied that carbohydrate distribution could, indeed, serve as an indication of the nutritional status of the trees. To measure NSC content efficiently, we attempted to quantify soluble carbohydrates and starch in dried and powdered tissues by visible-to-shortwave infrared (VIS-NIR-SWIR; 350–2500 nm) reflectance spectroscopy, which is an inexpensive, safe, and non-destructive technique. We applied several multivariate statistical models based on the spectral datasets, including partial least squares-regression (PLS-R) and discriminant analysis (PLS-DA) as supervised registration and classification models. PLS-DA results of the N gradient in the roots and leaves showed an overall accuracy of 94% and 98%, respectively. PLS-R model performances of soluble carbohydrates and starch improved, in terms of the coefficient of determination (R2), if the leaf and root samples were integrated. Moreover, we found that the SWIR spectral region (1100–2500 nm) had unique reflectance features that revealed the carbohydrate composition and starch concentrations in the different plant tissues. The analyses also clustered the reflectance by tree part (root, branch, or leaf tissues) and N availability, forming a holistic model that can identify the nutritional status of trees. Conclusively, it is suggested that reflectance spectroscopy at the SWIR spectral region could guide precise fertilization by high-throughput identification of plants’ seasonal metabolism.

Fall defoliation affects acquisition of freezing tolerance and spring regrowth in asparagus

Asparagus (Asparagus officinalis L.) acquires freezing tolerance during a period of fall acclimation when both photoperiod and temperature decrease. The above-ground vegetative growth may be important for sensing changing environmental conditions and translocating compounds to the below-ground crown. Defoliation experiments, repeated over 2 yr, were conducted by removing fern in mid-August, -September, and -October and evaluating crown metabolites and LT50, the temperature at which 50% of plants die, at monthly intervals to mid-November. Spring emergence and vigor were also assessed in separate experiments. In the first year, only mid-August defoliation affected LT50 values, decreasing freezing tolerance, which was associated with diminished rhizome proline concentration and storage root low- and high-molecular-weight fructan concentrations. All defoliation treatments in the second year decreased LT50 values, or increased freezing tolerance, possibly resulting from an interaction between defoliation and drought which increased rhizome sucrose concentrations. Defoliation decreased spring vigor in both experiments; the response was proportional to the earliness of the treatment and associated with rhizome and storage root fructan levels. Crowns of plants defoliated in mid-August had increasing proline concentrations during the fall, similar to control plants, suggesting the below-ground organs may have sensed soil temperature to cold acclimate. Autumn defoliation to control disease, harvest seed, or implement other cultural practices can reduce vigor and likely attenuate long-term performance of a plantation.

An Enzymatically Hydrolyzed Animal Protein-Based Biostimulant (Pepton) Increases Salicylic Acid and Promotes Growth of Tomato Roots Under Temperature and Nutrient Stress.

Biostimulants may be particularly interesting for application in agricultural and horticultural crops since they can exert a growth-promoting effect on roots. This may be important for promoting longitudinal and lateral root growth and therefore increasing belowground vegetative growth, which may in turn lead to improved aboveground vegetative growth and increased yields. Here, we examined the effects and mechanism of action of an enzymatically hydrolyzed animal protein-based biostimulant (Pepton) on the root growth of tomato plants, with an emphasis on its possible role on chorismate-derived hormones (auxin, salicylic acid, and melatonin). Tomato plants growing in hydroponic systems were exposed to either nutrient stress conditions (experiment 1) or suboptimal temperatures (experiment 2) in a greenhouse, and the concentration of auxin, salicylic acid, and melatonin in roots were measured just prior and after the application of the biostimulant. Results showed that the application of Pepton exerted a growth-promoting effect on roots in plants growing under suboptimal conditions, which might be associated with enhanced salicylic acid levels in roots. The extent of effects of this enzymatically hydrolyzed animal protein-based biostimulant might strongly depend on the growth conditions and stage of root system development. It is concluded that an enzymatically hydrolyzed animal protein-based biostimulant (Pepton) may exert a positive effect enhancing primary and lateral root growth of tomato plants growing under suboptimal conditions, by stimulating the biosynthesis of specific hormonal pathways, such as salicylic acid under stress.

Reconsidering the efficiency of grazing exclusion using fences on the Tibetan Plateau

Grazing exclusion using fences is a key policy being applied by the Chinese government to rehabilitate degraded grasslands on the Tibetan Plateau (TP) and elsewhere. However, there is a limited understanding of the effects of grazing exclusion on alpine ecosystem functions and services and its impacts on herders’ livelihoods. Our meta-analyses and questionnaire-based surveys revealed that grazing exclusion with fences was effective in promoting aboveground vegetation growth for up to four years in degraded alpine meadows and for up to eight years in the alpine steppes of the TP. Longer-term fencing did not bring any ecological and economic benefits. We also found that fencing hindered wildlife movement, increased grazing pressure in unfenced areas, lowered the satisfaction of herders, and rendered substantial financial costs to both regional and national governments. We recommend that traditional free grazing should be encouraged if applicable, short-term fencing (for 4–8 years) should be adopted in severely degraded grasslands, and fencing should be avoided in key wildlife habitat areas, especially the protected large mammal species.

Plasticity in Sexual Dimorphism Enhances Adaptation of Dioecious Vallisneria natans Plants to Water Depth Change.

Sexual dimorphism in vegetative and reproductive traits is associated with contrasting strategies of males and females for response to varied environmental conditions, causing sex-specific reproduction success and consequently long-distance dispersal and colonization. Aquatic plants usually exhibit rich phenotypic plasticity and great diversity in reproductive systems, but the influence of aquatic conditions on the plasticity of sexual dimorphism has received less attention. Using a common garden experiment with dioecious submerged plant Vallisneria natans grown at various water depths simulating different light availability, we measured variations in 20 traits for females and 19 traits for males (total = 540 plants from 30 seed families) including morphology, reproductive traits and photosynthesis. We investigated sex-specific plastic responses and variation of sexual dimorphism in response to water depth change. Females displayed much greater leaf length, vegetative biomass and resource allocation to reproduction than males at all depths, whereas spathe number and gamete production per spathe displayed reverse pattern. Besides most traits in each sex (16 in female and 12 in male) showing striking phenotypic plasticity, the degree of sexual dimorphism increased significantly for total biomass and reproductive investment, but decreased for leaf length, spathe number and flowering ramet percentage in low light and deep water. Females varied more than males in leaf length, total biomass, reproductive investment, length and biomass of reproductive organs and rate of photosynthesis in response to decreased underwater light availability, suggesting that female has greater plasticity than male. These findings illustrated considerable plasticity in the degree of sexual dimorphism in a variety of vegetative and reproductive traits across different environments driven by the contrasting reproductive functions of the sexes in relation to pollen and seed dispersal. Females of V. natans responded more plastically than males to low light conditions resulted from water depth variation in either aboveground vegetative growth or reproduction. This study provides novel insight into adaptive strategies of submerged dioecious macrophytes to survive and increase fitness in freshwater habitats.

Chemical root-pruning of Moringa oleifera for improved seedling growth

Low survival rates in greenhouse raised Moringa oleifera seedlings after transplanting had been ascribed to rapid growth rates and poorly formed and etiolated stems. The objective of the study was to determine the effect of indole acetic acid (IAA) on above-ground vegetative growth of M. oleifera seedling when used as root pruning agent. Hardened-off uniform one-month-old M. oleifera seedlings were transplanted in 20-cm-diameter plastic pots containing pasteurised loam soil and Hygromix at 3:1 (v/v) ratio. A week after transplanting, IAA concentrations of 0.0, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, 12.8, 25.6 and 51.2 mg mL−1 distilled water with G49 wetting agent and sticker were applied weekly to the respective plants. The effects of IAA concentrations were highly significant (P ≤ .01) on plant height, leaf number, dry root mass and significant (P ≤ .05) on stem diameter, which were further subjected to the lines of the best fit. Leaf number, plant height and stem diameter over increasing IAA concentrations exhibited positive quadratic relations, with the relationships being explained by 99, 98 and 98%, respectively. However, dry root mass and increasing concentrations of IAA exhibited negative quadratic relations, with the relationship being explained by 98%. At low concentrations, IAA increased plant height, number of leaves and stem diameter, whereas, at high concentration, the material reduced plant variables. However, all concentrations used reduced dry root mass. In conclusion, IAA was able to reduce root growth and promote shoot growth, with optimum for M. oleifera seedling growth established at a concentration level of 1.98 mg mL−1.

Aboveground biomass of the alpine shrub ecosystems in Three-River Source Region of the Tibetan Plateau

Though aboveground biomass (AGB) has an important contribution to the global carbon cycle, the information about storage and climatic effects of AGB is scare in Three-River Source Region (TRSR) shrub ecosystems. This study investigated AGB storage and its climatic controls in the TRSR alpine shrub ecosystems using data collected from 23 sites on the Tibetan Plateau from 2011 to 2013. We estimated the AGB storage (both shrub layer biomass and grass layer biomass) in the alpine shrubs as 37.49 Tg, with an average density of 1447.31 g m-2. Biomass was primarily accumulated in the shrub layer, which accounted for 92% of AGB, while the grass layer accounted for only 8%. AGB significantly increased with the mean annual temperature (P < 0.05). The effects of the mean annual precipitation on AGB were not significant. These results suggest that temperature, rather than precipitation, has significantly effects on of aboveground vegetation growth in the TRSR alpine shrub ecosystems. The actual and potential increase in AGB density was different due to global warming varies among different regions of the TRSR. We conclude that long-term monitoring of dynamic changes is necessary to improve the accuracy estimations of potential AGB carbon sequestration across the TRSR alpine shrub ecosystems.

Is grazing exclusion effective in restoring vegetation in degraded alpine grasslands in Tibet, China?

Overgrazing is considered one of the key disturbance factors that results in alpine grassland degradation in Tibet. Grazing exclusion by fencing has been widely used as an approach to restore degraded grasslands in Tibet since 2004. Is the grazing exclusion management strategy effective for the vegetation restoration of degraded alpine grasslands? Three alpine grassland types were selected in Tibet to investigate the effect of grazing exclusion on plant community structure and biomass. Our results showed that species biodiversity indicators, including the Pielou evenness index, the Shannon–Wiener diversity index, and the Simpson dominance index, did not significantly change under grazing exclusion conditions. In contrast, the total vegetation cover, the mean vegetation height of the community, and the aboveground biomass were significantly higher in the grazing exclusion grasslands than in the free grazed grasslands. These results indicated that grazing exclusion is an effective measure for maintaining community stability and improving aboveground vegetation growth in alpine grasslands. However, the statistical analysis showed that the growing season precipitation (GSP) plays a more important role than grazing exclusion in which influence on vegetation in alpine grasslands. In addition, because the results of the present study come from short term (6–8 years) grazing exclusion, it is still uncertain whether these improvements will be continuable if grazing exclusion is continuously implemented. Therefore, the assessments of the ecological effects of the grazing exclusion management strategy on degraded alpine grasslands in Tibet still need long term continued research.

The dynamics of resource allocation and costs of reproduction in a sexually dimorphic, wind-pollinated dioecious plant.

Sexual dimorphism in resource allocation is expected to change during the life cycle of dioecious plants because of temporal differences between the sexes in reproductive investment. Given the potential for sex-specific differences in reproductive costs, resource availability may contribute to variation in reproductive allocation in females and males. Here, we used Rumex hastatulus, a dioecious, wind-pollinated annual plant, to investigate whether sexual dimorphism varies with life-history stage and nutrient availability, and determine whether allocation patterns differ depending on reproductive commitment. To examine if the costs of reproduction varied between the sexes, reproduction was either allowed or prevented through bud removal, and biomass allocation was measured at maturity. In a second experiment to assess variation in sexual dimorphism across the life cycle, and whether this varied with resource availability, plants were grown in high and low nutrients and allocation to roots, aboveground vegetative growth and reproduction were measured at three developmental stages. Males prevented from reproducing compensated with increased above- and belowground allocation to a much larger degree than females, suggesting that male reproductive costs reduce vegetative growth. The proportional allocation to roots, reproductive structures and aboveground vegetative growth varied between the sexes and among life-cycle stages, but not with nutrient treatment. Females allocated proportionally more resources to roots than males at peak flowering, but this pattern was reversed at reproductive maturity under low-nutrient conditions. Our study illustrates the importance of temporal dynamics in sex-specific resource allocation and provides support for high male reproductive costs in wind-pollinated plants.

Potential impact of CO2 leakage from Carbon Capture and Storage (CCS) systems on growth and yield in maize

Anthropogenic release of CO2 is an important factor in the continuing rise in mean global temperature. Carbon capture and storage (CCS) offers a promising technology to capture and sequester CO2 in deep geological reservoirs. In view of the possible impact of leakage from CCS systems on vegetation, we examined the effects of elevated soil [CO2] on growth and yield in Zea mays L. Maize was exposed to elevated soil [CO2] by injecting CO2 at controlled rates using a purpose-designed field exposure facility. Measurements of soil [CO2] and [O2] revealed a strong negative correlation. Plants in a 40–90 cm diameter area centred on the injection point showed reduced growth and progressive development of severe stress symptoms during the gassing period. All above-ground vegetative (shoot, stem and leaf weight plant-1, chlorophyll content) and reproductive growth variables examined (mature cob and seed numbers plant-1) were negatively correlated with soil [CO2] and positively correlated with soil [O2]. Plants exposed to the highest [CO2] produced adventitious roots, possibly as an adaptive response to hypoxic soil conditions. Leakage from CCS transport or storage sites may have strong localised negative impacts on surface vegetation, the extent of which differs greatly between species.

The importance of urban backgardens on plant and invertebrate recruitment: a field microcosm experiment

Private backgardens in cities have the capacity to enhance ecological function and connectivity. The importance of increased habitat availability was tested experimentally using microcosms with soil or with soil and vegetation added into Toronto backgardens. Local attributes of the backgardens were recorded, and within the microcosms, recruitment of seeds, plants, and winged and wingless invertebrates were recorded. Natural recruitment by all organisms was significant into the microcosms in the 20 backgardens tested. Invertebrate abundance and diversity, incidental seed recruitment, and aboveground vegetation growth was enhanced regardless of whether only bare soil was added or soil with vegetation. The number of woody plants (non-herbaceous plants with hard lignified tissues or woody parts e.g., stems and are adapted to survive from one year to the next i.e., through winter) in the backgardens predicted seed recruitment and number of plant species predicted winged invertebrate abundance. Hence, simple augmentation of private backgardens—even at an ecologically small-scale—can enhance the capacity of urban systems to provide appropriate habitats for organisms within a difficult matrix for many species.

Role of transitory carbon reserves during adjustment to climate variability and source-sink imbalances in oil palm (Elaeis guineensis)

Oil palm (Elaeis guineensis Jacq.) is a perennial, tropical, monocotyledonous plant characterized by simple architecture and low phenotypic plasticity, but marked by long development cycles of individual phytomers (a pair of one leaf and one inflorescence at its axil). Environmental effects on vegetative or reproductive sinks occur with various time lags depending on the process affected, causing source-sink imbalances. This study investigated how the two instantaneous sources of carbon assimilates, CO(2) assimilation and mobilization of transitory non-structural carbohydrate (NSC) reserves, may buffer such imbalances. An experiment was conducted in Indonesia during a 22-month period (from July 2006 to May 2008) at two contrasting locations (Kandista and Batu Mulia) using two treatments (control and complete fruit pruning treatment) in Kandista. Measurements included leaf gas exchange, dynamics of NSC reserves and dynamics of structural aboveground vegetative growth (SVG) and reproductive growth. Drought was estimated from a simulated fraction of transpirable soil water. The main sources of variation in source-sink relationships were (i) short-term reductions in light-saturated leaf CO(2) assimilation rate (A(max)) during seasonal drought periods, particularly in Batu Mulia; (ii) rapid responses of SVG rate to drought; and (iii) marked lag periods between 16 and 29 months of environmental effects on the development of reproductive sinks. The resulting source-sink imbalances were buffered by fluctuations in NSC reserves in the stem, which mainly consisted of glucose and starch. Starch was the main buffer for sink variations, whereas glucose dynamics remained unexplained. Even under strong sink limitation, no negative feedback on A(max) was observed. In conclusion, the different lag periods for environmental effects on assimilate sources and sinks in oil palm are mainly buffered by NSC accumulation in the stem, which can attain 50% (dw:dw) in stem tops. The resulting dynamics of growth and production are complex because several dozen phytomers of different phenological ages develop at any given time and interact with a common pool of reserves.