Non-invasive determination of plant biomass with microwave resonators

Non-invasive and rapid determination of plant biomass would be beneficial for a number of research aims. Here, we present a novel device to non-invasively determine plant water content as a proxy for plant biomass. It is based on changes of dielectric properties inside a microwave cavity resonator induced by inserted plant material. The water content of inserted shoots leads to a discrete shift in the centre frequency of the resonator. Calibration measurements with pure water showed good spatial homogeneity in the detection volume of the microwave resonators and clear correlations between water content and centre frequency shift. For cut tomato and tobacco shoots, linear correlations between fresh weight and centre frequency shift were established. These correlations were used to continuously monitor diel growth patterns of intact plants and to determine biomass increase over several days. Interferences from soil and root water were excluded by shielding pots with copper. The presented proof of principle shows that microwave resonators are promising tools to quantitatively detect the water content of plants and to determine plant biomass. As the method is non-invasive, integrative and fast, it provides the opportunity for detailed, dynamic analyses of plant growth, water status and phenotype.     

重要值的改进及其在羊草群落分类中的应用

对重要值进行了改进, 首次提出了理论平均重要值(theoretical mean importance value, TMIV)、简化重要值(simple importance value, SIV)和样地指数(sample plot index, SPI)的概念。即, 理论平均重要值是指随物种数目变化样地内各种植物理论上的平均重要值。简化重要值是指理论平均重要值乘以某一植物的生物量与样地内所有植物的平均生物量的比值或者乘以某一植物的体积(盖度乘以高度)与样地内所有植物的平均体积的比值。样地指数是指简化重要值乘以某一植物的生物量与所有样地中该植物的平均生物量的比值或者乘以某一植物的体积与所有样地中该植物的平均体积的比值。相对重要值而言, 简化重要值减少了野外工作量。而样地指数既反映了物种在样地内所占有的优势, 又反映了物种在样地间所占有的优势, 使得不同样地的重要值更具可比性。文中用重要值、简化重要值和样地指数三个指标进行羊草群落的聚类分析, 结果表明, 简化重要值可用于植物群落的数量分类, 样地指数比重要值更适宜用于植物群落的数量分类。     

Ethanol yields and cell wall properties in divergently bred switchgrass genotypes

Genetic modification of herbaceous plant cell walls to increase biofuels yields is a primary bioenergy research goal. Using two switchgrass populations developed by divergent breeding for ruminant digestibility, the contributions of several wall-related factors to ethanol yields was evaluated. Field grown low lignin plants significantly out yielded high lignin plants for conversion to ethanol by 39.1% and extraction of xylans by 12%. However, across all plants analyzed, greater than 50% of the variation in ethanol yields was attributable to changes in tissue and cell wall architecture, and responses of stem biomass to dilute-acid pretreatment. Although lignin levels were lower in the most efficiently converted genotypes, no apparent correlation were seen in the lignin monomer G/S ratios. Plants with higher ethanol yields were associated with an apparent decrease in the lignification of the cortical sclerenchyma, and a marked decrease in the granularity of the cell walls following dilute-acid pretreatment.     

The long-term relationship between plant diversity and total plant biomass depends on the mechanism maintaining diversity

The relationship between plant diversity and total plant biomass is of great current interest in ecology. Niche differences among plants are widely thought to promote both plant coexistence, and higher biomass in more diverse polycultures. Using simple mechanistic models, I demonstrate that not all niche differences among plants are equally likely to promote high total biomass in polyculture. In particular, transgressive overyielding (when a polyculture of plants outperforms any monoculture) occurs for a wide range of parameter values when plants coexist in polyculture due to differences in resource use. Transgressive overyielding occurs only for a limited set of parameter values when specialist herbivores mediate plant coexistence, and is impossible when generalist herbivores mediate coexistence. Niche differences among plants promote high biomass in polyculture only when plants coexist in polyculture at the expense of other trophic levels – that is, by converting into biomass resources that would otherwise be bound in herbivores, or exist in a free state. A major challenge for future work will be to identify the joint consequences of different coexistence mechanisms for plant diversity and ecosystem performance.     

三峡库区岸生植物秋华柳对水淹的光合和生长响应

为阐明三峡库区岸生植物秋华柳(Salix variegata)对水淹的耐受机制,模拟三峡库区消落带水淹发生的情况,研究了在不同水淹时间和水淹深度处理下秋华柳的光合和生长特性。实验设置了对照(不进行水淹,常规供水管理)、水淹根部(植株置于水中,植株地下部分被淹没)、水下0.5 m(植株置于水中,植株顶部在水面下0.5 m)和水下2 m(植株置于水中,植株顶部在水面下2 m)4个不同的水淹深度和0、10、20、40、60和90 d 6个不同的水淹时间处理,并测定了在不同水淹时间和水淹深度处理下秋华柳的光合作用、叶绿素荧光和生长。研究结果发现:随着水淹时间的延长,对照和水淹根部植株都具有高的净光合速率、表观量子效率和羧化效率。水淹40 d后,相同水淹深度处理秋华柳植株的净光合速率显著高于耐水湿环境的垂柳(Salix babylonica)(p<0.05)。水淹90 d后,全淹处理植株的光合能力较对照有显著的下降(p<0.05),对照、水下0.5 m和水下2 m植株的净光合速率分别为13.2、10.1和8.05 μmol·m^-2·s^-1,同时全淹植株PSII的最大光化学效率也有一定程度的下降,显著低于对照和水淹根部处理的植株(p<0.05)。水淹40、60和90 d后,全淹植株的胞间CO₂浓度都高于对照和水淹根部植株。随着水淹时间的增加,水淹根部植株不定根数量不断增加,而全淹植株只有极少量的不定根产生。水淹根部植株的主茎长的增量、分枝数的增量、主茎新生叶片数、根生物量的积累和总生物量的积累都高于全淹植株,全淹植株在水淹过程中,其主茎长、分枝数、主茎新叶数、根生物量和总生物量都有增加,同时其凋落叶片较多。水淹90 d后,秋华柳植株的存活率为100%。研究结果表明,秋华柳在经过较长时间的水淹后,表现出较强的光合和生长适应性,可以考虑将秋华柳列为三峡库区消落带植被构建的物种之一。     

Chemical defense,mycorrhizal colonization and growth responses in <Emphasis Type="Italic">Plantago lanceolata</Emphasis> L.

Allelochemicals defend plants against herbivore and pathogen attack aboveground and belowground. Whether such plant defenses incur ecological costs by reducing benefits from plant mutualistic symbionts is largely unknown. We explored a potential trade-off between inherent plant chemical defense and belowground mutualism with arbuscular mycorrhizal fungi (AMF) in Plantago lanceolata L., using plant genotypes from lines selected for low and high constitutive levels of the iridoid glycosides (IG) aucubin and catalpol. As selection was based on IG concentrations in leaves, we first examined whether IG concentrations covaried in roots. Root and leaf IG concentrations were strongly positively correlated among genotypes, indicating genetic interdependence of leaf and root defense. We then found that root AMF arbuscule colonization was negatively correlated with root aucubin concentration. This negative correlation was observed both in plants grown with monocultures of Glomus intraradices and in plants colonized from whole-field soil inoculum. Overall, AMF did not affect total biomass of plants; an enhancement of initial shoot biomass was offset by a lower root biomass and reduced regrowth after defoliation. Although the precise effects of AMF on plant biomass varied among genotypes, plants with high IG levels and low AMF arbuscule colonization in roots did not produce less biomass than plants with low IG and high AMF arbuscule colonization. Therefore, although an apparent trade-off was observed between high root chemical defense and AMF arbuscule colonization, this did not negatively affect the growth responses of the plants to AMF. Interestingly, AMF induced an increase in root aucubin concentration in the high root IG genotype of P. lanceolata. We conclude that AMF does not necessarily stimulate plant growth, that direct plant defense by secondary metabolites does not necessarily reduce potential benefits from AMF, and that AMF can enhance concentrations of root chemical defenses, but that these responses are plant genotype-dependent.     

植株密度和氮素互作对垂穗披碱草生物量分配的影响

垂穗披碱草（Elymus nutans）是高寒地区建植和改良栽培草地的首选草种。虽然合理植株密度和氮素添加量是垂穗披碱草栽培草地稳产的关键因子,但两者之间是否存在最佳互作组合仍不清楚。采用盆栽试验,通过分析不同植株密度（58、102、146株/m²）和氮素添加量（0、200、400 mg/kg）组合状态下垂穗披碱草株高、单株分蘖数、地上生物量、地下生物量、根系体积和地上地下生物量比,以确定理论上是否存在植株密度和氮素添加量的最佳组合。结果表明：随植株密度增加,垂穗披碱草株高、地上生物量和地上地下生物量比值均先增加后降低,而单株分蘖数逐渐减小,根系体积和地下生物量先增加后保持相对稳定;随氮素添加量增加,垂穗披碱草单株分蘖数、地上生物量和地上地下生物量比值均表现为先增加后降低,地下生物量逐渐降低。植株密度与氮素添加量互作虽然对垂穗披碱草的根系体积和单株分蘖数没有显著影响,但两者互作显著影响了垂穗披碱草株高、地上生物量、地下生物量、地上地下生物量比（P<0.01）,这些指标与植株密度和氮素添加量的关系均表现为一个开口向下的抛物面。当植株密度为102株/m²和氮素添加量为200 mg/kg时,垂穗披碱草栽培草地产量最大,生物量分配最优。垂穗披碱草植株密度和氮素添加互作时理论上存在最佳组合,这为垂穗披碱草栽培草地的田间管理提供了理论依据。     

Maternal effects of drought stress and inbreeding in Impatiens capensis (Balsaminaceae)

Maternal effects can have substantial impacts on plant fitness and plant populations. Stressful environmental conditions can cause a maternal plant to inadequately provision its progeny, resulting in poor seedling growth, low reproductive success, and decreased competitive ability. Maternal effects consist of environmental and genetic load components, but the interactions between these two components have rarely been considered. To determine the effects of maternal drought stress and maternal inbreeding on progeny biomass (a fitness correlate) and physiological responses to drought stress, we conducted a greenhouse experiment with genetic lines from two populations (mesic site vs. dry site) of the herbaceous annual Impatiens capensis (Balsaminaceae). Seeds were collected from cleistogamous flowers of inbred or outcrossed maternal plants that were subject to either a drought or control treatment. These seeds were grown into juvenile plants that were also subject to either a drought stress or a control treatment. Plants from the mesic site had significantly reduced biomass from maternal drought stress, while plants from the dry site maintained biomass despite adverse maternal environmental conditions. Juvenile plants of both populations had reduced biomass only as a result of maternal inbreeding. Interestingly, inbreeding depression was more apparent when maternal environmental conditions were benign.     

Induction of a dwarf phenotype with IBH1 may enable increased production of plant‐made pharmaceuticals in plant factory conditions

Year‐round production in a contained, environmentally controlled ‘plant factory’ may provide a cost‐effective method to produce pharmaceuticals and other high‐value products. However, cost‐effective production may require substantial modification of the host plant phenotype; for example, using dwarf plants can enable the growth of more plants in a given volume by allowing more plants per shelf and enabling more shelves to be stacked vertically. We show here that the expression of the chimeric repressor for Arabidopsis AtIBH1 (P35S:AtIBH1SRDX) in transgenic tobacco plants (Nicotiana tabacum) induces a dwarf phenotype, with reduced cell size. We estimate that, in a given volume of cultivation space, we can grow five times more AtIBH1SRDX plants than wild‐type plants. Although, the AtIBH1SRDX plants also showed reduced biomass compared with wild‐type plants, they produced about four times more biomass per unit of cultivation volume. To test whether the dwarf phenotype affects the production of recombinant proteins, we expressed the genes for anti‐hepatitis B virus antibodies (anti‐HBs) in tobacco plants and found that the production of anti‐HBs per unit fresh weight did not significantly differ between wild‐type and AtIBH1SRDX plants. These data indicate that P35S:AtIBH1SRDX plants produced about fourfold more antibody per unit of cultivation volume, compared with wild type. Our results indicate that AtIBH1SRDX provides a useful tool for the modification of plant phenotype for cost‐effective production of high‐value products by stably transformed plants in plant factory conditions.     

SECONDARY SEX CHARACTERISTICS IN SPINACIA OLERACEA L.: QUANTITATIVE EVIDENCE FOR THE EXISTENCE OF AT LEAST THREE SEXUAL MORPHS

Spinacia oleracea L. was grown hydroponically across an experimental salinity gradient with treatments of 0.0, 1.5, 3.0, 4.5, and 6.0 grams of NaCl/liter of nutrient medium. Plant height, root biomass, vegetative biomass, fruit morphology, average fruit weight, and fruit mass: volume ratio were examined in each treatment to determine if differences other than primary sex characteristics exist between male, female, and monoecious plants. Average fruit weight was the only parameter examined that was not useful as a secondary sex characteristic. Orthogonal contrasts examining plant height, vegetative biomass, and root biomass of plants were distinct from one another across the salinity gradient. Similarly, female and monoecious plants differed significantly from one another in terms of root biomass and the average mass: volume ratio of the fruit each sexual morph produced, as well as the proportion of smooth to wrinkled fruit produced. The data indicate that male, female, and monoecious plants are three distinct sexual morphs.     

Moderate plant–soil feedbacks have small effects on the biodiversity–productivity relationship: A field experiment

Plant–soil feedback (PSF) has gained attention as a mechanism promoting plant growth and coexistence. However, most PSF research has measured monoculture growth in greenhouse conditions. Translating PSFs into effects on plant growth in field communities remains an important frontier for PSF research. Using a 4‐year, factorial field experiment in Jena, Germany, we measured the growth of nine grassland species on soils conditioned by each of the target species (i.e., 72 PSFs). Plant community models were parameterized with or without these PSF effects, and model predictions were compared to plant biomass production in diversity–productivity experiments. Plants created soils that changed subsequent plant biomass by 40%. However, because they were both positive and negative, the average PSF effect was 14% less growth on “home” than on “away” soils. Nine‐species plant communities produced 29 to 37% more biomass for polycultures than for monocultures due primarily to selection effects. With or without PSF, plant community models predicted 28%–29% more biomass for polycultures than for monocultures, again due primarily to selection effects. Synthesis: Despite causing 40% changes in plant biomass, PSFs had little effect on model predictions of plant community biomass across a range of species richness. While somewhat surprising, a lack of a PSF effect was appropriate in this site because species richness effects in this study were caused by selection effects and not complementarity effects (PSFs are a complementarity mechanism). Our plant community models helped us describe several reasons that even large PSF may not affect plant productivity. Notably, we found that dominant species demonstrated small PSF, suggesting there may be selective pressure for plants to create neutral PSF. Broadly, testing PSFs in plant communities in field conditions provided a more realistic understanding of how PSFs affect plant growth in communities in the context of other species traits.     

基因工程在能源植物改良中的应用

利用基因工程技术改良能源植物,对降低能源植物向生物燃料(生物乙醇、生物柴油)的转化成本、提高能源转化效率有着非常重要的意义。目前,基因工程技术已被广泛应用于提高植物总的生物产量、降低或改变植物木质素的含量与成分、在植物体中大量表达纤维素降解酶、提高油料植物的产油量以及改变植物油酯的组成成分等方面的研究。概述了利用基因工程技术在以上方面对能源植物进行改良已取得的进展,讨论了现存问题及未来的发展前景。     

Plant competition and exclusion with optimizing individuals

Most models of plant competition represent competition as taking place between species when realistically competition takes place between individuals. We model individual plants as optimally choosing biomass in order to maximize net energy that is directed into reproduction. Competition is for access to light and a plant that grows more biomass adds to the leaf area index, creating negative feedback in the form of more self shading and shading of its neighbors. In each period and for given species densities, simultaneous maximization by all plants yields an equilibrium characterized by optimum biomasses. Between periods the net energies plants obtain are used to update the densities, and if densities change the equilibrium changes in the subsequent period. A steady state is attained when all plants have net energies that just allow for replacement. Four main predictions of the resource-ratio theory of competition are obtained, providing behavioral underpinnings for species level models. However, if individual plant parameters are not identical across species, then the predictions do not follow. The optimization framework yields many other predictions, including how specific leaf areas and resource stress impact biomass and leaf area indices.     

Linear relationships between aboveground biomass and plant cover in low open herbaceous vegetation

Abstract. Four herbaceous plant species of a sand dune area and several herb species of an open early‐successional patch were investigated for the occurrence of a simple relationship between aboveground biomass and plant cover. Without exception linear regressions of aboveground biomass on plant cover were found with slope factors depending on the growth form of the species. These results suggest that (early) growth of herbaceous plants in low and (temporarily) open vegetation is not affected by possible constraints caused by a decreasing ratio of plant cover to aboveground biomass. The obtained linear relationships could be used for rapid non‐destructive determination of aboveground biomass by image‐analysis of cover data.     

Short photoperiod attenuates CO2 fertilization effect on shoot biomass in Arabidopsis thaliana

The level of carbon dioxide (CO₂) in the air can affect several traits in plants. Elevated atmospheric CO₂ (eCO₂) can enhance photosynthesis and increase plant productivity, including biomass, although there are inconsistencies regarding the effects of eCO₂ on the plant growth response. The compounding effects of ambient environmental conditions such as light intensity, photoperiod, water availability, and soil nutrient composition can affect the extent to which eCO₂ enhances plant productivity. This study aimed to investigate the growth response of Arabidopsis thaliana to eCO₂ (800 ppm) under short photoperiod (8/16 h, light/dark cycle). Here, we report an attenuated fertilization effect of eCO₂ on the shoot biomass of Arabidopsis plants grown under short photoperiod. The biomass of two-, three-, and four-week-old Arabidopsis plants was increased by 10%, 15%, and 28%, respectively, under eCO₂ compared to the ambient CO₂ (aCO₂, 400 ppm) i.e. control. However, the number of rosette leaves, rosette area, and shoot biomass were similar in mature plants under both CO₂ conditions, despite 40% higher photosynthesis in eCO₂ exposed plants. The levels of chlorophylls and carotenoids were similar in the fully expanded rosette leaves regardless of the level of CO₂. In conclusion, CO₂ enrichment moderately increased Arabidopsis shoot biomass at the juvenile stage, whereas the eCO₂-induced increment in shoot biomass was not apparent in mature plants. A shorter day-length can limit the source-to-sink resource allocation in a plant in age-dependent manner, hence diminishing the eCO₂ fertilization effect on the shoot biomass in Arabidopsis plants grown under short photoperiod.     

Modeling the Individual Growth of Tetrahymena Sp. and its Population Consequences

ABSTRACT. Three types of mathematical growth models are presented to describe the individual growth of the ciliate Tetrahymena sp. feeding on the bacterium Pseudomonas fluorescens . Both organisms were isolated from a domestic waste-water treatment plant. Growth of individual ciliates and the consequences for the whole population are considered. Experimental data, obtained by following the individual ciliate during its lifespan from cell division to cell division, are used for parameter estimations. Differences between growth models for individuals turn out to have little effect on the specific population growth rate and the mean cell volume. In case of exponential growth of individuals the unstructured and structured population models are equivalent, even in time-variant environments. This knowledge can be applied in the stability analysis of food chains or forced systems. The results obtained facilitates quantification of protozoa biomass as a function of bacterial biomass in chemostats. More specifically, it highlights the dynamic behaviour of bacteria and protozoa in waste-water treatment plants.     

Biomass accumulation and partitioning, photosynthesis, and photosynthetic induction in field-grown maize (Zea mays L.) under low- and high-nitrogen conditions

The objectives of this comparative study were to investigate the responses of biomass accumulation and partitioning to nitrogen supply and to examine the effect of low-nitrogen supply on the photosynthetic responses of maize leaves to steady-state and dynamic light. While the difference in leaf number and stem diameter was not statistically significant, there was a significant difference in plant height between the low-nitrogen and high-nitrogen maize plants. During grain-filling period, the ear leaf of the low-nitrogen maize plants possessed lower values of maximum photosynthetic rate, maximum stomatal conductance, maximum transpiration rate, apparent quantum yield, light compensate point, and carboxylation efficiency than did that of the high-nitrogen maize plants. Contrarily, lower values of intercellular CO₂ concentration and dark respiration rate were observed in the high-nitrogen maize plants. In addition, a slower response to simulated sunflecks was found in the ear leaf of the low-nitrogen maize plants; however, stomatal limitations did not operate in the ear leaf of the high-nitrogen or low-nitrogen maize plants during the photosynthetic induction. As compared to the high-nitrogen maize plants, the low-nitrogen maize plants accumulated much less plant biomass but allocated a greater proportion of biomass to belowground parts. In conclusion, our results suggested that steady-state photosynthetic capacity is restricted by both biochemical and stomatal limitation and the photosynthetic induction is constrained by biochemical limitation alone in low-nitrogen maize plants, and that maize crops respond to low-nitrogen supply in a manner by which more biomass was allocated preferentially to root tissues.     

外来入侵植物小飞蓬种群构件生物量结构特征

小飞蓬是我国分布最广的外来入侵物种之一,通过样方调查,从构件水平研究了小飞蓬各构件的结构特征及其生物量间的关系模型,并进行了定量分析。结果表明小飞蓬各构件生物量间的关系表现为茎>叶>根>花;各构件生物量在个体生物量中所占比率也表现为茎>叶>根>花;小飞蓬根、茎、叶生物量与植株高度及各构件生物量间均呈正相关关系。     

Allometry of Salsola collina in response to soil nutrients,water supply and population density

The allometry of greenhouse‐grown Salsola collina Pall. in response to variation in soil nutrient content, water supply and population density has been compared. The results showed that the biomass allocation was size‐dependent. Root, stem, leaf and reproductive allocation showed a ‘true’ plasticity in response to soil nutrient variation. At low soil nutrient content, plants tended to allocate more biomass to the development of reproductive organs than to stem and leaf, but root allocation was consistent due to a tradeoff between the effects of plant size and soil nutrient content. The plasticity of stem allocation and reproductive effort was ‘true’, while the plasticity of root allocation was ‘apparent’, but there was no plasticity for leaf allocation in response to soil water variation. At lower soil water content, plants tended to allocate more biomass to the stem than to development of reproductive organs. With the exception of ‘apparent’ plasticity of root allocation, no plasticity was detected in biomass allocation when population density was varied.