Annual Plant Growth Research Articles

AINTEGUMENTA-LIKE genes regulate reproductive growth and bud dormancy in Platanus acerifolia.

Platanus acerifolia AIL genes PaAIL5a/b and PaAIL6b participate in FT-AP1/FUL-AIL pathways to regulate bud dormancy. In addition, PaAIL6a/b can promote flowering, and PaAIL5b and PaAIL6b affect floral development. Bud dormancy and floral induction are essential processes for perennial plants, they are both regulated by photoperiod, temperature, and hormones, indicating the existence of common regulators for both processes. AINTEGUMENTA-LIKE (AIL) genes regulate reproductive growth of annual plants, including floral induction and flower development, and their homologs in poplar and grape act downstream of the florigen gene FT and the floral meristem identity genes AP1/FUL and function to maintain growth and thus inhibit dormancy induction. However, it is not known whether AIL homologs participate in the reproduction processes in perennials and whether the Platanus acerifolia AIL genes are involved in dormancy. P. acerifolia is a perennial woody plant whose reproductive growth is strongly associated with dormancy. Here, we isolated four AIL homologs from P. acerifolia, PaAIL5a, PaAIL5b, PaAIL6a, and PaAIL6b, and systematically investigated their functions by ectopic-overexpression in tobacco. The findings demonstrate that PaAIL5a/b and PaAIL6b respond to short day, low temperature, and hormone signals and act as the components of the FT-AP1/FUL-AIL pathway to regulate the bud dormancy in P. acerifolia. Notably, PaAIL5a/b and PaAIL6b function downstream of PaFTL-PaFUL1/2/3 to inhibit the dormancy induction and downstream of PaFT-PaFUL2/3 to promote the dormancy release. In addition, PaAIL6a/b were found to accelerate flowering in transgenic tobacco, whereas PaAIL5b and PaAIL6b affected the flower development. Together, our results suggest that PaAIL genes may act downstream of different PaFT/PaFTL and PaFUL proteins to fulfill conservative and diverse roles in floral initiation, floral development, and dormancy regulation in P. acerifolia.

Asparagus (Asparagus officinalis L.) Root Distribution: Cultivar Differences in Mature Plantings

Annual plant growth patterns and seasonal conditions have both been shown to influence asparagus (Asparagus officinalis L.) root development over time. Root biomass and distribution changes in mature asparagus cultivars are herein illustrated and described. Asparagus root length density and biomass were estimated from soil cores using a systematic field sampling approach each spring. Soil cores (0.9 m deep) were divided into 0.15 m lengths and fleshy roots collected from the soil. Root length density and dry weights were determined and root distribution maps generated from collected data. As asparagus plantings matured, the sampling year had a significant influence on root development. Fleshy roots grew deeper into the soil each year but the majority of roots of Atlas, Guelph Millennium, and Jersey Giant were found in the upper 60 cm of the soil profile. For the three cultivars evaluated, minor differences in root length and root weight occurred. By Year 6, Atlas showed a decrease in root length and weight when compared to Guelph Millennium and Jersey Giant. While spear yield differences between the varieties were not significant, Atlas tended to produce more very large and large spears compared to Guelph Millennium and Jersey Giant. These results increase our understanding of asparagus root development.

Scientific basis of the effect of groundwater sources on annual plant growth in current natural conditions

Low groundwater temperatures lead to longer plant growth periods. For example, the growth and development of cotton and grain are delayed by 7-15 days. All this ultimately affects the yield and quality of the agricultural crop and the ripening period of its fruits. In turn, the low-temperature water-air soil environment of the aeration zone does not ensure the timely dissolution of natural and artificial nutrients and fertilizers and does not allow their timely full assimilation by plant root systems. Under such conditions, some of these nutrients sink under the influence of falling currents of cold water and mix with groundwater. On the other hand, a cold aquatic-airy soil environment of 14–18 C° is detrimental to cotton, significantly reduces the rate of growth and development, and exposes it to various diseases. All this ultimately affects the yield and quality of the agricultural crop, and the ripening period of its fruits.

Asparagus (Asparagus officinalis L.) Root Distribution Varies with Cultivar during Early Establishment Years

Soil type, crop management practices, annual plant growth patterns, and seasonal changes have all been shown to influence asparagus (Asparagus officinalis) roots. This study describes the changes in root growth that occur over the three establishment seasons of three asparagus cultivars. Starting one year after planting, asparagus root length density and biomass were estimated from soil cores (55 mm diam. × 0.2 m long) collected to 0.9 m at three locations adjacent to the row (0.15, 0.3, and 0.6 m from row center). Samples were collected each spring during the spear harvest period (late April to early May). Soil cores were divided into 0.15 m lengths and fleshy roots were collected for the soil, root length density determined, and dry weights measured. The year of sampling had a significant effect on root development and, as time progressed, fleshy asparagus roots grew deeper into the soil. There was no difference in fleshy root length or fresh weight between the three cultivars evaluated. However, root distribution patterns varied between the cultivars. Fleshy roots for the cultivars Atlas and Jersey Giant extended further from the crown and deeper in the soil when compared to Guelph Millennium. Results can be used to improve crop management practices and increase our understanding of the dynamic changes of root development that occur over time in asparagus.

Green roofs sown with an annual plant mix attain high cover and functional diversity regardless of irrigation frequency

Annual plant species have great potential on green roofs as many are highly attractive, fast and cheap to establish via sowing and can provide rapid cover and growth, which is important for ecosystem service provision. While irrigation is essential for survival and growth of annual plants in seasonally hot or dry climates, it is also important to minimize water use as availability is often limited. Therefore, we evaluated how irrigation frequency affects plant cover, species abundance, richness and diversity, plant traits and functional diversity of a 16 species mixture of Australian annual species (4 g m−2 ~ 2100 seeds m−2) sown onto thirty 0.25 m2 green roof modules. The experiment was carried out in Melbourne, Australia, from January (summer) to July (winter) 2020. After a 2-month irrigated establishment phase (to ensure germination and seedling establishment), three irrigation treatments (2, 4 and 6 days between irrigation) were applied to the modules for three months. Plant cover was reduced at lower irrigation frequency (6 days), but ≥ 80% plant cover was achieved in all irrigation treatments. There was no effect of irrigation frequency on species abundance and richness; however, abundance, richness and diversity reduced over time, likely due to competition effects. Plant height and leaf area were also reduced by lower irrigation frequency. At the community level, functional diversity was unaffected by irrigation frequency. Our results indicate that green roofs sown with a mixture of annual plants can achieve good plant coverage, as recommended by green roof guidelines, and maintain high diversity when minimally irrigated in their first growing season.

Investigating the applicability of UAVs in characterizing desert shrub biomass and developing biological indicators for the selection of suitable revegetation sites

This study focused on evaluating factors influencing the growth of perennial shrubs by integrating field-based experiments and spatial analysis using unmanned aerial vehicles (UAVs) to identify ecological indicators that can help detect potential locations for restoration and revegetation of native plants. The experiment was implemented in the Al-Abduli protected area in Kuwait, which is mainly dominated by a Rhanterium epapposum community (desert shrub). Aerial imagery of the study site was acquired using UAVs during the growing season to estimate the desert shrub biomass and carbon stock. Then, soil samples were collected based on vegetation density to determine the impact of the soil's physical and chemical properties on vegetation biomass, growth, and distribution. It was found that shrub biomass was significantly correlated with crown area and shrub volume. We also observed that annual plants support the growth of perennial shrubs, as the mean shrub height and crown area (CA) are significantly higher, with averages of 0.7 m and 3 cm, respectively, in the presence of high annual plant density. However, shrubs in plots with low annual density had an average shrub height of 0.5 m and CA of 1.4 cm. Annual plants also enhance the soil by providing approximately 50% higher soil moisture, phosphorous (P), organic matter (OM), and carbon dioxide (CO2) sequestration. In addition, annual plants are mainly supported by loamy soils in the deeper soil layers. We concluded that locations covered with annual plants represent suitable soils and that this can be considered a biological indicator for convenient locations for restoration and revegetation of native perennial shrubs. Remote sensing technologies could be utilized for initial assessments to detect sites that may support annual plant growth over a large scale for classification as potential restoration and revegetation areas.

Summer irrigation of pasture enhances the transfer and short-term storage of soil organic carbon in the particulate and mineral-associated organic matter fractions

Soil organic carbon (SOC) is both a source and sink of atmospheric carbon dioxide (CO2), with important implications for global climate change. Irrigation of grazed pastures has reportedly increased, reduced or made no difference to SOC stocks relative to dryland management. This study examined, over an annual plant growth cycle, the persistence of photosynthate-derived carbon (C) previously allocated to the plant–soil system during summer, under irrigated or dryland conditions. A continuous 13CO2 pulse labelling method was used to label ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) mesocosms under simulated dryland or irrigated conditions. Plant and soil 13C was traced over 349 days using destructive sampling on days 1, 12, 125, 237 and 349 (T1–T5 respectively). After the cessation of labelling and summer irrigation, the mesocosms were maintained under the same seasonal soil moisture conditions. The persistence of 13C in the aboveground plant C pools was lower than in the root C pool. Approximately 50% of the initial mass of 13C recovered in roots at T1 remained by T5. There was no difference between the summer irrigated and dryland treatments in terms of the 13C recovered from the soil over the subsequent annual growing season. There was also no significant change in the 13C recovered in the soil between T1 and T5. However, summer irrigation did affect the spatial and temporal distribution of the photosynthate-derived C within the soil size fractions relative to summer dryland conditions. Summer irrigation promoted the transfer and storage of 13C in the fine particulate organic matter and clay size fractions.

Different Cover Crops Affect Nitrogen Fluxes in Mediterranean Vineyard

Core Ideas Burr medic cover crop supplied 125 kg ha–1 year–1 of fixed N to the vineyard. Twice the N needs of grapevine annual organs were satisfied by legume cover crop. Legume cover crop promoted + 25% of total N compared to grass cover crop. Compared to traditional soil tillage, the establishment of cover crops in Mediterranean vineyards has several advantages such as better soil fertility; however, vigor and N concentration of grapevine [Vitis vinifera (L.)] organs may be affected. A 3‐yr experiment was performed in Sardinia (Italy) to: (i) quantify the N fixation ability by burr medic [Medicago polymorpha (L.)] grown in a vineyard and its potential benefit for grapevines; (ii) compare the effects of different management systems (grass or legume cover crop vs. soil tillage) on grapevines. Total N fixed by burr medic was 125 kg ha−1 yr−1 and it was twice as high as the N contents of grapevine annual organs. Soil tillage promoted higher cluster and cane dry matter (+38% and +31%), compared to cover crop treatments. Legume cover crop induced higher N concentration in leaves and canes. The N content detected in grapevine annual plant growth with the legume cover crop reached 61 kg ha−1 yr−1. According to an indirect 15N dilution approach, the higher 15N enrichments detected in organs of grapevines, did not indicate that legume N was utilized by grapevine. However, lower 15N enrichment was occasionaly detected, indicating 6 and 13% of N derived from legume in clusters and canes, respectively. Compared to grapevines with grass cover, the N contribution from legume cover, estimated by the N‐difference method, induced 24, 24, and 31% of N increase in leaves, clusters, and canes, respectively. The increases corresponded to 10% of legume fixed N.

Land surface phenology derived from normalized difference vegetation index (NDVI) at global FLUXNET sites

Phenology is an important indicator of annual plant growth and is also widely incorporated in ecosystem models to simulate interannual variability of ecosystem productivity under climate change. A comprehensive understanding of the potentials of current algorithms to detect the start and end for growing season (SOS and EOS) from remote sensing is still lacking. This is particularly true when considering the diverse interactions between phenology and climate change among plant functional types as well as potential influences from different sensors. Using data from 60 flux tower sites (376 site-years in total) from the global FLUXNET database, we applied four algorithms to extract plant phenology from time series of normalized difference vegetation index (NDVI) from both MODIS and SPOT-VGT sensors. Results showed that NDVI-simulated phenology had overall low correlation (R2<0.30) with flux-derived SOS/EOS observations, but this predictive strength substantially varied by fitting algorithm, sensor and plant functional type. Different fitting algorithms can produce significantly different phenological estimates, but this difference can also be influenced by sensor type. SPOT-VGT simulated better EOS but no difference in the accuracy of SOS was found with different sensors. It may be due to increased frequency of data sampling (10 days for SPOT-VGT vs. 16 days for MODIS) during spring season when rapid plant growth does not help SPOT-VGT more sensitive to growth. In contrast, more frequent data acquisition favors better modeling of plant growth in autumn when a gradual decrease in photosynthesis occurs. Our study results highlight that none of these algorithm can provide consistent good accuracy in modeling SOS and EOS with respect to both plant functional types and sensors. More importantly, a rigorous validation of phenology modeling against ground data is necessary before applying these algorithms at regional or global scales and consequently previous conclusions on regional SOS/EOS trends should be viewed with caution if independent validation is lacking.

시설원예단지 조성이 농업생태계의 식생다양성에 미치는 영향 분석

인간은 생태계로부터 다양한 공익적 기능을 제공받고 있지만 시설원예단지 조성은 불투수면적 확장과 생물서식처 손실로 인해 기능저하의 원인이 될 수 있다. 시설원예단지 조성이 식물 종 다양성에 미치는 영향을 파악하였다. 식생분포 특성 분석결과 논에 비해 시설원예단지의 식물다양성이 상당히 낮다는 것을 알 수 있었다. 따라서 저 영향개발, 서식공간 배치, 식물 보전, 화학비료 사용제한, 서식처 조성, 보전비용 등을 제안하였다. 생활형 분석을 통해 일년생식물과 수생식물의 생육기반 환경 조성을 제시하였다. 귀화식물은 총 10과 20종류가 확인되었으며, 귀화율은 유리온실과 연동형 온실이 매우 높게 분석되어 콘크리트 피복을 지양하고 자연토양 피복을 유도 할 것을 제안하였다. 연구결과는 통계분석을 통해 확인하고 불투수면적을 자연형 토양으로 전환을 제안하였다. 본 연구결과는 지속가능한 농업경관 유지와 대규모 간척지 개발 사업에 있어 친환경, 생태적 시설원예단지 조성을 위한 정책자료에 활용되길 기대한다. Although the ecosystem extends numerous functions for the benefit of humankind, construction of horticultural facilities can potentially lead to the degeneration of some of these functions owing to the expansion of impervious regions and loss of habitats. Thus, this study aimed to examine the effect of construction of horticultural facilities on plant biodiversity. Analysis of the vegetation distribution characteristics showed that horticultural facilities had significantly lower plant diversity than did rice paddies. Hence, the proposed approach involved low-impact development, arrangement of habitat space, plant preservation, restricted use of chemical fertilizer, habitat creation, and reduced preservation cost. Lifestyle analysis suggested the importance of developing favorable environments for the growth of annual plants and aquatic plants. In all, 20 species of naturalized plants belonging to 10 families were identified. Furthermore, the proportion of these naturalized plants was higher in glass greenhouses and multi-span greenhouses, suggesting the advantages of employing natural soil mulching while avoiding concrete mulching. Statistical analysis was performed to validate the results, which suggested that impervious regions be converted to natural soils. Collectively, the findings of this study are expected to be used for establishing policies for the construction of eco-friendly and ecological horticultural facilities; this may aid the maintenance of sustainable agricultural landscapes and large-scale development of the reclaimed lands.

Characteristics of preferential flow during simulated rainfall events in an arid region of China

Little is known about preferential flow and its effects on vegetation under natural conditions in an arid oasis ecotone. In this study, we performed dye-tracer experiments using 5, 15, 35, and 55 mm water-sprinkling treatments at three sites: Grass (G), Haloxylon (H), and Populus (P). At each site, we determined soil texture and saturated hydraulic conductivity of the soil (K s) and water flow parameters; we also defined characteristics of soil fracturing and measured plant biomass at site P. The tracer experiments revealed that the three sites displayed significant differences in the degree of preferential flow. Soil structure and surface characteristics were the primary controlling factors, however, they played a different role in different rainfall events. For small rainfall events, soil surface characteristics controlled the preferential flow pattern; for large or extreme rainfall events, soil structure was the critical factor. The effects of different rainfall events were complex and strongly varied among sites. Our results further indicated that preferential flow could impact the growth of annual plants. We conclude that preferential flow in an arid oasis ecotone is a common phenomenon affected by complex factors, and it may be important in soil water distribution and plant growth.

Goat trampling affects plant establishment, runoff and sediment yields over crusted dunes

AbstractMainly attributed to goat and sheep trampling, the sand dunes at the Israeli and the Egyptian sides of the border present contrasting geomorphological conditions. In an attempt to assess the trampling effect upon vegetation, runoff and sediment yield, two pairs of plots and miniplots (each pair contains a trampled plot and a control) were constructed during 1991 and monitored during 1991–1995. In order to assess the impact on vegetation, three pairs of vegetation plots, subjected to light, medium and heavy trampling, were established during 1993 and monitored. In addition, the effect of the micro structures created by the goat hooves (mounds and depressions) were studied in three pairs of plots subjected to medium trampling during 1993 and monitored during 1993–1996. As far as trampling intensity is concerned, the findings indicate an increase in species diversity, density and biomass from the intact crusted surface to the plots subjected to light and medium trampling with a decrease thereafter at the plots subjected to heavy trampling. As for the micro scale, the findings indicate significantly higher plant biomass for the first 2 years at the hooves‐formed mini mounds and mini depressions in comparison to intact crusted surfaces, with no significant difference during the third year. Significantly lower runoff and sediment yields characterized the trampled plots implying a reduction in water redistribution. The data point to the differential effect that trampling has upon plants and soil. While increasing annual plant growth along the slope, it hinders runoff flow to the footslope, negatively affecting water availability for footslope vegetation. Recovery, as also supported by chlorophyll and microrelief measurements, was scale dependent (attributed to differential supply of aeolian sand) with estimated recovery for the plots and miniplots being 4–5 and 8–10 years, respectively. The data indicate that upon the cessation of grazing and under similar precipitation regime, recovery time of the biocrust in the Sinai sand dunes may be short, within 5–6 years. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Effects of rainfall patterns on annual plants in Horqin Sandy Land, Inner Mongolia of China

Growth of annual plants in arid environments depends largely on rainfall pulses. An increased understanding of the effects of different rainfall patterns on plant growth is critical to predicting the potential responses of plants to the changes in rainfall regimes, such as rainfall intensity and duration, and length of dry intervals. In this study, we investigated the effects of different rainfall patterns (e.g. small rainfall event with high frequency and large rainfall event with low frequency) on biomass, growth characteristics and vertical distribution of root biomass of annual plants in Horqin Sandy Land, Inner Mongolia of China during the growing season (from May to August) of 2014. Our results showed that the rainfall patterns, independent of total rainfall amount, exerted strong effects on biomass, characteristics of plant growth and vertical distribution of root biomass. Under a constant amount of total rainfall, the aboveground biomass (AGB), belowground biomass (BGB), plant cover, plant height, and plant individual and species number increased with an increase in rainfall intensity. Changes in rainfall patterns also altered the percentage contribution of species biomass to the total AGB, and the percentage of BGB at different soil layers to the total BGB. Consequently, our results indicated that increased rainfall intensity in future may increase biomass significantly, and also affect the growth characteristics of annual plants.

The negative effect of biocrusts upon annual-plant growth on sand dunes during extreme droughts

Following recent findings that biocrusts (known also as biological soil crusts) enhance the evaporation of the underlying soil in the dune field in the Negev Desert (P = 95 mm), an attempt is made to evaluate the effect of biocrust on plant germination and growth during drought years. Periodical (mainly weekly) moisture measurements of the upper 30 cm layer were conducted at 5 habitats of formerly defined biocrust types and at 4 non-crusted habitats during 2010/11 and 2011/12 (extreme drought years with 30.4 and 35.2 mm, respectively). At the end of each growing season, the species composition, cover and biomass of the annual plants was measured. While only limited germination and annual-plant maturation took place in the crusted habitats during 2011/12, no germination was recorded at the crusted habitats during 2010/11, explained by enhanced evaporation due to lower albedo of the biocrusts. In contrast, annual-plant germination and maturation took place at the non-crusted habitats during both years. Contrary to the common view that regards sand dunes as infertile and hostile for plant growth while highlighting the positive role of biocrusts on plants, the current findings indicate that as far as annual plant productivity is concerned, the non-crusted dune may serve as a fertility belt for annuals during extreme drought years.

Estimate of the Carbon Dioxide Uptake by the Urban Green Space for a Carbon–Neutral Sejong City in Korea

Atmospheric carbon dioxide (CO2) is the main indicator of global warming and consumption of fossil fuels by humans. The Intergovernmental Panel on Climate Change (IPCC) emphasized on mitigation technologies, practices, and policies to reduce CO2 emissions in urban sectors, which included forest management and land–use regulation. Since the enforcement of a special law to construct a multifunctional administrative city, named “Sejong City,” in 2005, the city aims to achieve the goal of a “Carbon–Neutral Sejong” through maximizing CO2 uptake by urban green space and its surrounding forest as well as reducing CO2 emissions in association with environmentally friendly urban planning, energy efficient building design, and renewable energy use during the planning phase. This research aims to make a preliminary estimate of the annual CO2 uptake by urban green space in the city and the peripheral areas via a bottom–up approach based on the established Sejong City Master Plan for Construction. In addition, the annual CO2 uptake estimate is compared with the annual CO2 emission estimate from literature sources, and recommendations are made based on the findings. The annual CO2 uptake by the city's urban green space is estimated at 70,641 tCO2/yr based on the annual plant growth, and the CO2-uptake-to-emission ratio, from the use of fossil fuels in buildings, is estimated at 2.3%, based on the Sejong City Master Plan.

An Annual Plant Growth Proxy in the Mojave Desert Using MODIS-EVI Data.

In the arid Mojave Desert, the phenological response of vegetation is largely dependent upon the timing and amount of rainfall, and maps of annual plant cover at any one point in time can vary widely. Our study developed relative annual plant growth models as proxies for annual plant cover using metrics that captured phenological variability in Moderate-Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) satellite images. We used landscape phenologies revealed in MODIS data together with ecological knowledge of annual plant seasonality to develop a suite of metrics to describe annual growth on a yearly basis. Each of these metrics was applied to temporally-composited MODIS-EVI images to develop a relative model of annual growth. Each model was evaluated by testing how well it predicted field estimates of annual cover collected during 2003 and 2005 at the Mojave National Preserve. The best performing metric was the spring difference metric, which compared the average of three spring MODIS-EVI composites of a given year to that of 2002, a year of record drought. The spring difference metric showed correlations with annual plant cover of R2 = 0.61 for 2005 and R2 = 0.47 for 2003. Although the correlation is moderate, we consider it supportive given the characteristics of the field data, which were collected for a different study in a localized area and are not ideal for calibration to MODIS pixels. A proxy for annual growth potential was developed from the spring difference metric of 2005 for use as an environmental data layer in desert tortoise habitat modeling. The application of the spring difference metric to other imagery years presents potential for other applications such as fuels, invasive species, and dust-emission monitoring in the Mojave Desert.

Influence of mixed LED radiation on the growth of annual plants

We investigated the effect of mixed radiation from light-emitting diodes (LEDs) on the growth and flowering of ageratum, marigold, and salvia bedding plants. Blue, red, and far-red lights were applied under controlled environmental conditions for 28 d. Both the combination of blue-plus-red radiation as well as fluorescent lighting treatment (control) caused increases in dry weights, but shoot lengths were shortest when plants were exposed to blue plus red light compared with either red or blue plus far-red treatments. The number of floral buds as well as the occurrence of flower opening for ageratum and salvia plants was also enhanced under the blue plus red mixture. Likewise, carbohydrate accumulation was stimulated by that combination compared with the other radiation treatments.

Plant allometry, leaf nitrogen and phosphorus stoichiometry, and interspecific trends in annual growth rates.

Life forms as diverse as unicellular algae, zooplankton, vascular plants, and mammals appear to obey quarter-power scaling rules. Among the most famous of these rules is Kleiber's (i.e. basal metabolic rates scale as the three-quarters power of body mass), which has a botanical analogue (i.e. annual plant growth rates scale as the three-quarters power of total body mass). Numerous theories have tried to explain why these rules exist, but each has been heavily criticized either on conceptual or empirical grounds. N,P-STOICHIOMETRY: Recent models predicting growth rates on the basis of how total cell, tissue, or organism nitrogen and phosphorus are allocated, respectively, to protein and rRNA contents may provide the answer, particularly in light of the observation that annual plant growth rates scale linearly with respect to standing leaf mass and that total leaf mass scales isometrically with respect to nitrogen but as the three-quarters power of leaf phosphorus. For example, when these relationships are juxtaposed with other allometric trends, a simple N,P-stoichiometric model successfully predicts the relative growth rates of 131 diverse C3 and C4 species. The melding of allometric and N,P-stoichiometric theoretical insights provides a robust modelling approach that conceptually links the subcellular 'machinery' of protein/ribosomal metabolism to observed growth rates of uni- and multicellular organisms. Because the operation of this 'machinery' is basic to the biology of all life forms, its allometry may provide a mechanistic explanation for the apparent ubiquity of quarter-power scaling rules.

Effects of root‐applied naringenin and chalcone on the growth of annual plants

Effects of root‐applied naringenin and chalcone on the growth of annual plants

Growth and abundance of desert annuals in an arid woodland in Oman

Research on the ecology of annual plants inhabiting deserts of Western Asia that have low rainfall and warm winter temperatures is extremely limited. One ecological factor that may greatly affect ephemeral growth in these deserts is rainfall interception by trees and large shrubs. Biologists have clarified how perennial plant foliage intercepts and re-distributes rainfall, but very little research has focused on the impact this may have on annual plant growth. Previous qualitative observations in this arid woodland suggest that rainfall intensity and microenvironment may interact to influence ephemeral plant production. This research quantifies the spatial patterns of the growth and abundance of an ephemeral plant community at three microsites, two beneath samr trees (Acacia tortilis (Forsskal) Hayne) and one in open desert, through five successive rainfall events. Two variables, density and dry weight biomass, were quantified on 0.25 m–2 quadrats placed at mid-canopy beneath mature trees and in open inter-spaces. For both variables, there was a significant interaction between exposure and rainfall (P = 0.001), indicating that differences in biomass and density among the microsites were dependent on each rain event. The potential role of the trees in this interaction and in determining patterns of soil moisture and plant growth is discussed. Eight annuals showed strong preferences for certain exposures under the trees. This is the first report of very fine-scale differences (1-2 meters) in the distribution of desert ephemerals. Relationships between the ecological preferences, the various microclimates and the plants' distinctive photosynthetic physiologies are outlined, as well as the relevance of this research to facilitation theory.