Biomass Partitioning Research Articles

Biomass partitioning and nutrient fluxes in Silphium perfoliatum and silage maize cropping systems

Cup plant cultivation as feedstock for anaerobic digestion has become an emerging topic in European Agriculture. Although there is a gap in methane yields between cup plant and the benchmark crop silage maize, cup plant as a perennial crop provides several ecological advantages. Amongst others, studies have proven its potential for carbon sequestration. With the present study, we addressed the gap in knowledge about biomass partitioning above- and belowground as well as recycling of organic matter and nutrients for cup plant and compared the results to silage maize. Therefore, a 2 year field experiment was conducted under practical conditions on rather shallow soil conditions in a low mountain landscape in Western Germany. Relevant plant fractions like litterfall, yield biomass and stubbles were collected continuously and analyzed for their nutrient contents. Results show that the cup plant is characterized by more than 2000 kg ha− 1 a− 1 of pre-harvest losses with a high palatability. In sum, only 77% of the grown cup plant biomass can be harvested in contrast to 96% of silage maize. Thus, an intense, element-specific nutrient recycling takes place in cup plant whereas this is negligible in silage maize. Furthermore, clearly different, element-specific nutrient exports with yield were highlighted. In cup plant, exports were distinctly lower for nitrogen but several times higher for calcium compared to silage maize. Cup plant also showed 36% more roots with higher root masses particularly in the subsoil.Graphical abstract

Sink-source unbalance leads to abnormal partitioning of biomass and nitrogen in rice under extreme heat stress: An experimental and modeling study

Extreme heat stress occurred frequently with increasing global warming, and significantly reduced crop yield. Experimental and modelling studies for grain yield formation under heat stress were widely carried out, but carbohydrate and nitrogen re-distribution caused by unbalanced sink-source relationships have rarely been noticed. The multi-year experimental datasets involving different heat stress intensities, durations, and rice varieties showed that rice stem was re-activated as a sink organ during grain filling stage after short-term extreme heat stress at flowering, where a large amount of carbohydrate and nitrogen accumulated. The stems may become alternative harvest organs under climate change, whereas needs accurate assessments for adaptation strategy. We further improved the simulation of biomass and nitrogen accumulation in different rice organs according to the re-evaluated sink-source relationship under heat stress, based on RiceGrow model. The nitrogen filling process in stems after the termination of grain filling was quantified, and the delay of leaf senescence was also simulated by accounting for the leaf nitrogen distribution within the canopy under heat stress. The improved model explained the cause and effect of unusual carbohydrate and nitrogen accumulation under heat stress in rice, and can be a useful tool for adaptation strategy under climate change.

Effects of Exogenous L-Asparagine on Poplar Biomass Partitioning and Root Morphology.

L-Asparagine (Asn) has been regarded as one of the most economical molecules for nitrogen (N) storage and transport in plants due to its relatively high N-to-carbon (C) ratio (2:4) and stability. Although its internal function has been addressed, the biological role of exogenous Asn in plants remains elusive. In this study, different concentrations (0.5, 1, 2, or 5 mM) of Asn were added to the N-deficient hydroponic solution for poplar 'Nanlin895'. Morphometric analyses showed that poplar height, biomass, and photosynthesis activities were significantly promoted by Asn treatment compared with the N-free control. Moreover, the amino acid content, total N and C content, and nitrate and ammonia content were dramatically altered by Asn treatment. Moreover, exogenous Asn elicited root growth inhibition, accompanied by complex changes in the transcriptional pattern of genes and activities of enzymes associated with N and C metabolism. Combined with the plant phenotype and the physiological and biochemical indexes, our data suggest that poplar is competent to take up and utilize exogenous Asn dose-dependently. It provides valuable information and insight on how different forms of N and concentrations of Asn influence poplar root and shoot growth and function, and roles of Asn engaged in protein homeostasis regulation.

Additive Allometric Equations to Improve Aboveground Biomass Estimation for Mongolian Pine Plantations in Mu Us Sandy Land, Inner Mongolia, China

Afforestation is conducive to improving ecosystem service functions and ecosystem diversity in the Mu Us Sandy Land, however, the important attribute of biomass for Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantations has yet to be accurately evaluated. This study aimed to develop additive allometric biomass equations for the species and evaluate biomass partitioning patterns within tree components. A total of 131 trees were measured for stem, branch, and leaf biomass by destructively sampling and tree climbing, with the latter as a supplement. For each biomass component, we tested three equations with the diameter at breast (D) alone, height (H) as additional, and diameter in combination with height (D2H) as predictors using the weighted least squared method. Weighted nonlinear seemingly unrelated regression was adopted to fit a system of additive allometric biomass equations utilizing the selected equations. A leave-one-out cross-validation method (the jackknife procedure) was used to assess the predictive ability. The biomass partitioning pattern was evaluated by calculating the ratios. The results revealed that the diameter alone is a good predictor for branches and foliage biomass estimates, while the stem requires H included to improve estimation accuracy. Mongolian pine allocates relatively more biomass to the crown (51.4%) compared to the stem (48.6%). Branch biomass fraction increased monotonously with increasing tree size while a reverse trend was observed for foliage. In conclusion, the additive models developed in this study provide a robust biomass estimation and can be extensively used to estimate Mongolian pine forests biomass in Mu Us Sandy Land.

Biomass, Carbon and Nitrogen Partitioning and Water Use Efficiency Differences of Five Types of Alpine Grasslands in the Northern Tibetan Plateau.

(1) Background: Grassland covers most areas of the northern Tibetan Plateau along with important global terrestrial carbon (C) and nitrogen (N) pools, so there is a need to better understand the different alpine grassland growth associated with ecosystem C, N storage and water use efficiency (WUE). (2) Methods: The plant biomass and C, N concentrations, stocks and vegetation WUE of five kinds of alpine grassland types were investigated in northern Tibetan Plateau. (3) Results: The results showed that there were significant differences among five types of alpine grasslands in aboveground biomass (AGB), belowground biomass (BGB), total biomass (TB) and root:shoot (R/S) ratio while the highest value of different indices was shown in alpine meadow type (AM). The AGB and BGB partitioning results significantly satisfied the allometric biomass partitioning theory. The C, N concentrations and C/N of the vegetation in AGB and BGB showed significant grassland type differences. The highest C, N stocks of BGB were in AM which was almost six or seven times more than the C, N stocks of AGB in alpine desert type (AD). There were significant differences in δ13C and intrinsic water use efficiency (WUEi) under five alpine grassland types while the highest mean values of foliar δ13C and WUEi were in AD. Significant negative correlations were found between WUEi and C, N concentrations, C/N of AGB and soil water content (SWC) while the correlation with BGB C/N was not significant. For AGB, BGB, TB and R/S, there were positive correlations with C, N concentrations of AGB, BGB and SWC while it had significant negative correlations with C/N of BGB. (4) Conclusions: With regard to its types, it is suggested that the AM or AS may be an actively growing grassland type in the northern Tibetan Plateau.

Simulating the effects of low-temperature stress on wheat biomass growth and yield

Low-temperature stress in late spring poses a serious threat to winter wheat production. In three-year environment-controlled phytotron experiments at both elongation and booting stages, we observed that short-term low-temperature stress decreased leaf area and stem, limited leaf photosynthetic system, and severely reduced grain yield, especially in the low-temperature sensitive cultivar. To better quantify the effects of low-temperature stress on leaf photosynthesis rate (Pn), leaf area index (LAI), biomass partitioning, and grain yield, the lethal temperature at 50% mortality (LT50), low-temperature damage index (LDI), and process-based algorithms were proposed and incorporated into the WheatGrow model. The algorithms take into account the effects of low-temperature with different durations and reflected a low-temperature sensitivity of cultivars at different growth periods by using LT50. The improved WheatGrow model could reproduce well the observed dynamics of the decrease of Pn during the treatment period, recovery of Pn after cold treatments, and the damage to LAI and biomass accumulation under the low-temperature stress treatments. Compared to the original model, RMSE of Pn, LAI, total aboveground biomass, and grain yield in the improved WheatGrow model were reduced by 63 to 77% under low-temperature stress. Although the newly developed algorithms expand crop modeling capacity into quantifying the impacts of low-temperature stress on wheat productivity, further assessments with observed data under field conditions are still required, especially for obtaining suitable parameters at the regional scale.

Biomass Partitioning and Morphoanatomical Traits of Six Gymnocalycium (Cactaceae) Species Occurring along a Precipitation Gradient

As a group, cacti are regarded as plants that tolerate water scarcity, since they present a number of adaptations. However, little is known about how species of the family varied their morphoanatomical characteristics along environmental gradients. The aim of this study was to analyze how six Gymnocalycium species occurring in three sites along a precipitation gradient (arid site: G. pugionacanthum, G. marianae; semiarid site: G. hybopleurum, G. stellatum; subhumid site: G. oenanthenum, G. baldianum) differ in their biomass partitioning and morphoanatomical characteristics. We collected mature individuals of each species and analyzed their biomass partitioning (to spines, aboveground stem, underground stem, main root, and lateral and thin roots), morphological characteristics (such as size ratios, spine length and width, and areole density) and anatomical characteristics (stoma number, and cuticle, epidermis, and hypodermis width). Species differed, both qualitatively and quantitatively, in most of the analyzed variables. For example, biomass allocated to spines was highest in G. pugionacanthum, lowest in G. baldianum, and intermediate in the remaining species. However, these variations were not clearly associated with aridity, but were related to the subgenus of the species. These patterns were clearly observed in the PCA. Phylogenetic relatedness is the main factor associated with morphoanatomical characteristics.

Genetic dissection of nitrogen induced changes in the shoot and root biomass of spinach

Efficient partitioning of above and below-ground biomass in response to nitrogen (N) is critical to the productivity of plants under sub-optimal conditions. It is particularly essential in vegetable crops like spinach with shallow root systems, a short growth cycle, and poor nitrogen use efficiency. In this study, we conducted a genome-wide association study (GWAS) to explore N-induced changes using spinach accessions with diverse genetic backgrounds. We evaluated phenotypic variations as percent changes in the shoot and root biomass in response to N using 201 spinach accessions grown in randomized complete blocks design in a soilless media under a controlled environment. A GWAS was performed for the percent changes in the shoot and root biomass in response to N in the 201 spinach accessions using 60,940 whole-genome resequencing generated SNPs. Three SNP markers, chr4_28292655, chr6_1531056, and chr6_37966006 on chromosomes 4 and 6, were significantly associated with %change in root weight, and two SNP markers, chr2_18480277 and chr4_47598760 on chromosomes 2 and 4, were significantly associated with % change shoot weight. The outcome of this study established a foundation for genetic studies needed to improve the partitioning of total biomass and provided a resource to identify molecular markers to enhance N uptake via marker-assisted selection or genomic selection in spinach breeding programs.

Maize prolificacy under contrasting plant densities and N supplies: II. Growth per plant, biomass partitioning to apical and sub-apical ears during the critical period and kernel setting

Maize ( Zea mays L.) prolificacy (i.e., more than one fertile ear per plant) is a source of reproductive plasticity that contributes to increase or sustain crop grain yield when plant density is reduced in drought-prone environments. The rare use of N fertilization, however, can limit prolificacy. In a companion paper we studied floret differentiation and biomass allocation in apical (E1) and sub-apical ear (E2) and flowering dynamics of five maize hybrids with contrasting prolificacy under different plant densities and N supplies. Briefly, after apex induction, E1 and E2 of the most prolific hybrids (DK-3F22, DK-4F37 and DK-664) had similar temporal patterns of growth and floret differentiation. On the contrary, E2 in the less prolific hybrids (DK-747 and DK-7210) had less biomass allocation and floret differentiation than E1, which were reduced under low soil N supply, resulting in a fewer proportion of plants with silk extrusion of E2. In this work, we explore the relationships between (i) kernel number per plant vs the growth rates of plants around flowering, (ii) growth rate of ears vs plant growth rate around flowering (i.e. biomass partitioning to E1 and E2), (iii) kernel number of E1 and E2 vs the growth rates of ears around flowering (i.e. reproductive efficiency of E1 and E2), and (iv) kernel number and prolificacy vs flowering synchrony (i.e., ASI: anthesis-silking interval and ESI: ear silking interval between E1 and E2). For all hybrids, N supply modulated plant growth rate and biomass partitioning to both ears around flowering, kernel number per unit of plant growth rate around flowering and reproductive efficiency of E2, with no impact on the reproductive efficiency of E1. Reductions of kernel number per plant were related to failures of early emerged silks (of E1 under low N supply and of E2 under both N supplies) to set kernels. Failures in kernel setting of E2 were also related to a reduced biomass partitioning to E2 around flowering. Higher ASI E1 values described crops with lower kernel numbers of E1, while higher ESI values depicted both a lower proportion of plants with more than one fertile ear (i.e., prolificacy) and lower kernel numbers of E2. Results complement evidence from the companion paper of the role of N supply on plant biomass production and biomass partitioning to E2 from early floral development stages to the period around flowering, and on the reproductive efficiency of E2. Consequently, N supply must be ensured from early vegetative stages of low-density maize crops, so as not to compromise prolificacy and E2 kernel setting. • Prolificacy was highly sensitive to N supply even at low plant density. • High N supply increased biomass partitioning to ears around flowering. • Only reproductive efficiency of sub-apical ear (E2) was improved by N supply. • Ear silking interval modulate prolificacy expression and kernel setting of E2.

CLM5-FruitTree: a new sub-model for deciduous fruit trees in the Community Land Model (CLM5)

Abstract. The inclusion of perennial, woody crops in land surface models (LSMs) is crucial for addressing their role in carbon (C) sequestration, food production, and water requirements under climate change. To help quantify the biogeochemical and biogeophysical processes associated with these agroecosystems, we developed and tested a new sub-model, CLM5-FruitTree, for deciduous fruit orchards within the framework of the Community Land Model version 5 (CLM5). The model development included (1) a new perennial crop phenology description, (2) an adapted C and nitrogen allocation scheme, considering both storage and photosynthetic growth of annual and perennial plant organs, (3) typical management practices associated with fruit orchards, and (4) the parameterization of an apple plant functional type. CLM5-FruitTree was tested using extensive field measurements from an apple orchard in South Tyrol, Italy. Growth and partitioning of biomass to the individual plant components were well represented by CLM5-FruitTree, and average yield was predicted within 2.3 % of the observed values despite low simulated inter-annual variability compared to observations. The simulated seasonal course of C, energy, and water fluxes was in good agreement with the eddy covariance (EC) measurements owing to the accurate representation of the prolonged growing season and typical leaf area development of the orchard. We found that gross primary production, net radiation, and latent heat flux were highly correlated (r>0.94) with EC measurements and showed little bias (<±5 %). Simulated respiration components, sensible heat, and soil heat flux were less consistent with observations. This was attributed to simplifications in the orchard structure and to the presence of additional management practices that are not yet represented in CLM5-FruitTree. Finally, the results suggested that the representation of microbial and autotrophic respiration and energy partitioning in complex, discontinuous canopies in CLM5 requires further attention. The new CLM5-FruitTree sub-model improved the representation of agricultural systems in CLM5 and can be used to study land surface processes in fruit orchards at the local, regional, or larger scale.

Acclimation of Ecophysiological and Agronomic Traits to Increasing Growth Temperature in Three Cowpea Genotypes Grown in Anuradhapura, Sri Lanka

The future of food crop production is uncertain due to the negative effects of global warming. Cowpea is grown in warm environments including in Sri Lanka, where less is known about the potential acclimation of ecophysiological and agronomic traits to increasing temperatures. We evaluated the acclimation potential of yield components and ecophysiological traits of three recommended cowpea genotypes to the seasonal variation in growth temperature in Anuradhapura, Sri Lanka. This study was conducted at the Faculty of Agriculture, Rajarata University of Sri Lanka, in two consecutive seasons with average daytime temperatures of 30.4°C and 33.2°C. Three genotypes, Dhawala, Waruni, and MI-35, were tested in this study, and their rates of leaf photosynthesis and respiration at the 50% flowering stage and final yield parameters were measured at their respective average growth temperatures in both seasons. The total yield per hectare showed an average decrease of 16%, 17%, and 22% in the Dhawala, Waruni, and MI-35 genotypes at high average growth temperature, respectively. These reductions were associated with the reduction in the number of seeds per pod, hundred seed weight, and number of pods per plant, suggesting that there could be an among-genotype variation in flower abscission, fertilization, and biomass partitioning during the season in which the average growth temperature was high. In the season with high average growth temperature, genotype Dhawala showed an increased carbon gain per unit carbon loss and increased water use efficiency compared to MI-35 and Waruni genotypes. Therefore, genotype Dhawala is a better candidate than MI-35 and Waruni genotypes in the face of global warming, which may be considered in further breeding programs and market preferences. More work is proposed to examine the patterns of biomass partitioning and radiation use efficiency in three cowpea genotypes at elevated temperatures.

Epigenetic and Phenotypic Responses to Experimental Climate Change of Native and Invasive Carpobrotus edulis.

Despite the recent discoveries on how DNA methylation could help plants to adapt to changing environments, the relationship between epigenetics and climate change or invasion in new areas is still poorly known. Here, we investigated, through a field experiment, how the new expected climate scenarios for Southern Europe, i.e., increased temperature and decreased rainfall, might affect global DNA methylation in relation to phenotypic variation in individuals of clonal plant, Carpobrotus edulis, from its native (Southern African) and invaded (northwestern Iberian Peninsula) area. Our results showed that changes in temperature and rainfall induced phenotypic but not global DNA methylation differences among plants, and the climatic effects were similar for plants coming from the native or invaded areas. The individuals from the Iberian Peninsula showed higher levels of global methylation than their native counterparts from South Africa. We also observed differences between natives and invasive phenotypes in traits related to the pattern of biomass partitioning and to the strategies for water uptake and use and found an epigenetic contribution to phenotypic changes in some leaf traits, especially on the nitrogen isotopic composition. We conclude that the increased temperature and decreased rainfall projected for Southern Europe during the course of the twenty-first century may foster phenotypic changes in C. edulis, possibly endowing this species with a higher ability to successful cope the rapid environmental shifts. The epigenetic and phenotypic divergence that we observed between native and invasive plants suggests an intraspecific functional variation during the process of invasion. This result could indicate that phenotypic plasticity and global DNA methylation are related to the colonization of new habitats. Our findings reinforce the importance of epigenetic plasticity on rapid adaptation of invasive clonal plants.

Elevated light intensity compensates for nitrogen deficiency during chrysanthemum growth by improving water and nitrogen use efficiency

Identifying environmental factors that improve plant growth and development under nitrogen (N) constraint is essential for sustainable greenhouse production. In the present study, the role of light intensity and N concentrations on the biomass partitioning and physiology of chrysanthemum was investigated. Four light intensities [75, 150, 300, and 600 µmol m−2 s−1 photosynthetic photon flux density (PPFD)] and three N concentrations (5, 10, and 15 mM N L−1) were used. Vegetative and generative growth traits were improved by increase in PPFD and N concentration. High N supply reduced stomatal size and gs in plants under lowest PPFD. Under low PPFD, the share of biomass allocated to leaves and stem was higher than that of flower and roots while in plants grown under high PPFD, the share of biomass allocated to flower and root outweighed that of allocated to leaves and stem. As well, positive effects of high PPFD on chlorophyll content, photosynthesis, water use efficiency (WUE), Nitrogen use efficiency (NUE) were observed in N-deficient plants. Furthermore, photosynthetic functionality improved by raise in PPFD. In conclusion, high PPFD reduced the adverse effects of N deficiency by improving photosynthesis and stomatal functionality, NUE, WUE, and directing biomass partitioning toward the floral organs.

Effect of spatial position on twig resource allocation of Fengdan (Paeonia ostii)

AbstractUnderstanding how a plant allocates biomass for reproduction and the effect of location position on twigs' biomass partitioning provides essential information on how to maximise fruit yields through pruning. Fengdan (Paeonia ostii) is a variety of oil Peony newly developed in China. In this paper, the pattern of biomass allocation and allometric growth of the modules within twig (fruit twigs) of five populations of Fengdan were investigated by using standardised major axis (SMA) analyses. The ANOVA results showed that the biomass of stem, seed, husk and fruit per twig significantly varied among populations and among twigs growing at different positions within an individual plant. The top twig had the largest stem and fruit biomass. Twig showed an allometric growth relationship between reproduction and growth (SMA slope b ≠ 1). An obvious trade‐off was found between seed number and 100‐seed weight in fruits. These findings demonstrate that the seated position of the Fengdan twig significantly influences its resource allocation pattern and fruit (seed) yield, implying the efficiency of creating a suitable growth environment and optimising tree architecture in increasing oil Peony yield.

Biomass and mineral nutrient partitioning among self-pollinated and cross-pollinated fruit on the same strawberry plant.

Pollen-parent effects on fruit size and quality have been found previously among competing self-pollinated and cross-pollinated fruit on the same Redlands Joy strawberry plant. These effects occur independently of the percentage of fertilized seeds on the fruit, but the expression of these effects on fruit size and some aspects of quality are greatest when calcium is in shortest supply. Here, we aimed to clarify at what developmental stages the self-pollinated and cross-pollinated fruit diverge in size and quality and whether differences between self-pollinated and cross-pollinated fruit are due to early differences in nutrient accumulation. Fruit were harvested at 1, 2 and 3 weeks after hand-pollination and at full ripeness, approximately 4 weeks after hand-pollination. We measured fruit mass, length, diameter, colour, and the concentrations of aluminium, boron, calcium, copper, iron, nitrogen, magnesium, manganese, sodium, phospho-rous, potassium and zinc. Temporary increases in fruit mass, length or diameter due to cross-pollination were evident at 1 or 2 weeks after pollination. Consistent increases in size and skin darkness from cross-pollination emerged in the final week of fruit development. We found little evidence that self-pollinated and cross-pollinated fruit differed in mineral nutrient accumulation at any stage of fruit development. The results demonstrate that cross-pollination effects on strawberry fruit size are evident briefly during early fruit growth but emerge mainly during the final week of fruit development. The effects of cross-pollination on fruit size are not the result of early differences in mineral nutrient accumulation between self-pollinated and cross-pollinated fruit.

Growth, biomass partitioning and chlorophyll fluorescence response to drought stress: a comparative study of Commelina communis L. biotypes

Growth, biomass partitioning and chlorophyll fluorescence response to drought stress: a comparative study of Commelina communis L. biotypes

Effect of salinity and different light on biomass sharing of the ornamental species euphorbia milii and zamioculcas zamiifolia

Part of the Northeast region of Brazil presents abiotic limitations for the production of flowers and ornamental plants, especially salinity and excessive solar radiation. This research aimed to test the effects of increasing salinity levels and different light conditions on the biomass partitioning of the ornamental species Euphorbia milii and Zamioculcas zamiifolia. The experimental design was in randomized blocks in subdivided plots, with five repetitions, with the plots referring to the environmental factor (full sun, 30, 50 and 70% shade), the subplots to the salinity levels in the irrigation water - ECw (0.5; 2.0; 3.5; and 5.0 dS m-1), and the subplots to the ornamental species Euphorbia milii and Zamioculcas zamiifolia, with two plants per repetition, totaling 320 experimental units. Shading at 30% stimulated greater biomass partitioning to flowers, however, at higher shading levels a reduction in the proportion of flowers and an increase in biomass in leaves was observed in the Euphorbia milii species. Zamioculcas zamiifolia allocated the highest biomass fraction (about 65% of photoassimilates) to the roots and rhizomes at all salinity levels, but shading had little influence on photoassimilate partitioning in this species.

Growth responses of Avicennia germinans and Batis maritima seedlings to weathered light sweet crude oil applied to soil and aboveground tissues.

Oil spills are a significant stressor to coastal and maritime environments worldwide. The growth responses of Batis maritima and Avicennia germinans seedlings to weathered Deepwater Horizon oiling were assessed through a mesocosm study using a factorial arrangement of 4 soil oiling levels (0 L m-2, 1 L m-2, 2 L m-2, 4 L -m-2) × 3 tissue oiling levels (0% of stem height, 50% of stem height, 100% of stem height). Overall, growth metrics of B. maritima displayed much greater sensitivity to both tissue and soil oiling than A. germinans, which exhibited a relatively high tolerance to both routes of oiling exposure. Batis maritima in the 4 L m-2 soil oiling treatment demonstrated significant reductions in cumulative stem height and leaf number, whereas no significant effects of soil oiling on A. germinans were detected. This was reflected in the end of the study biomass partitioning, where total aboveground and live aboveground biomass were significantly reduced for B. maritima with 4 L m-2 soil oiling, but no impacts to A. germinans were found. Tissue oiling of 100% did appear to reduce B. maritima stem diameter, but no effect of tissue oiling was discerned on biomass partitioning, suggesting that there were no impacts to integrated growth. These findings suggest that B. maritima would be more severely affected by moderate soil oiling than A. germinans.

Seedling Growth and Quality of Avicennia marina (Forssk.) Vierh. under Growth Media Composition and Controlled Salinity in an Ex Situ Nursery

Avicennia marina (Forssk.) Vierh. is an important mangrove species that inhabits the outermost zone of mangrove forests, but it has been shown to have a poor ability to regenerate due to its low seedling quality. We conducted a study to evaluate the specific growth requirements of A. marina, i.e., medium and salinity level. Germinated seeds were transplanted to pots filled with media, i.e., silt loam (M1), loam (M2), sandy loam (M3), or sand (M4), with various salinity levels 5 (S1), 5–15 (S2), 15–25 (S3), or 25–35 ppt (S4). Survival rate, growth, biomass partition, and seedling quality were observed for 14 weeks after transplanting the seeds. The highest rate of seedling survival was found in the S2 condition, and higher concentrations of salinity lowered the survival rates. The S1 treatment promoted the initial 8 week growth of the seedlings. Growth medium had no significant effect, except on the survival rates grown in M4. Growth medium composition had no distinct effect on seedling growth. The S2 and S3 treatments induced better growth (in terms of shoot height and root length) and resulted in high-quality (i.e., Dickson quality index) seedlings in any type of medium. The S3 treatment increased the seedling quality in M1 and M4, whereas the S4 treatment only benefited seedlings in the M4 medium. According to the results, a specific range of salinity (5–15 ppt) with circulated water in any type of medium is recommended for the establishment of an ex situ nursery for the propagation of A. marina, in contrast to the general range of salinity (4–35 ppt) stated in previous references.

Biomass partitioning of plants under soil pollution stress

Polluted sites are ubiquitous worldwide but how plant partition their biomass between different organs in this context is unclear. Here, we identified three possible drivers of biomass partitioning in our controlled study along pollution gradients: plant size reduction (pollution effect) combined with allometric scaling between organs; early deficit in root surfaces (pollution effect) inducing a decreased water uptake; increased biomass allocation to roots to compensate for lower soil resource acquisition consistent with the optimal partitioning theory (plant response). A complementary meta-analysis showed variation in biomass partitioning across published studies, with grass and woody species having distinct modifications of their root: shoot ratio. However, the modelling of biomass partitioning drivers showed that single harvest experiments performed in previous studies prevent identifying the main drivers at stake. The proposed distinction between pollution effects and plant response will help to improve our knowledge of plant allocation strategies in the context of pollution.