Total Biomass Accumulation Research Articles

Exogenous trehalose improves growth under limiting nitrogen through upregulation of nitrogen metabolism

BackgroundThe trehalose (Tre) pathway has strong effects on growth and development in plants through regulation of carbon metabolism. Altering either Tre or trehalose 6-phosphate (T6P) can improve growth and productivity of plants as observed under different water availability. As yet, there are no reports of the effects of modification of Tre orT6P on plant performance under limiting nutrition.ResultsHere we report that nitrogen (N) metabolism is positively affected by exogenous application of Tre in nitrogen-deficient growing conditions. Spraying foliage of tobacco (Nicotiana tabacum) with trehalose partially alleviated symptoms of nitrogen deficiency through upregulation of nitrate and ammonia assimilation and increasing activities of nitrate reductase (NR), glycolate oxidase (GO), glutamine synthetase (GS) and glutamine oxoglutarate aminotransferase (GOGAT) with concomitant changes in ammonium (NH4+) and nitrate (NO3−) concentrations, glutamine and amino acids. Chlorophyll and total nitrogen content of leaves and rates of photosynthesis were increased compared to nitrogen-deficient plants without applied Tre. Total plant biomass accumulation was also higher in Tre -fed nitrogen-deficient plants, with a smaller proportion of dry weight partitioned to roots, compared to nitrogen-deficient plants without applied Tre. Consistent with higher nitrogen assimilation and growth, Tre application reduced foliar starch. Minimal effects of Tre feeding were observed on nitrogen-sufficient plants.ConclusionsThe data show, for the first time, significant stimulatory effects of exogenous Tre on nitrogen metabolism and growth in plants growing under deficient nitrogen. Under such adverse conditions metabolism is regulated for survival rather than productivity. Application of Tre can alter this regulation towards maintenance of productive functions under low nitrogen. This has implications for considering approaches to modifying the Tre pathway for to improve crop nitrogen-use efficiency and production.

Yield formation of Central-European winter wheat cultivars on a large scale perspective

Abstract Improvement of grain yield potential for winter wheat ( Triticum aestivum ) may become harder to achieve in the future because an increase of harvest index has been largely exploited by breeders. Therefore, it is of high interest to detect how the components of the yield equation GY = Q × LUE × HI ( GY : grain yield, Q : radiation interception, LUE : light use efficiency, HI : harvest index) contribute to the explanation of yield differences of modern high yielding wheat varieties. To gain more insight in the variability of the parameters in the above equation and their contribution to grain yield, a field experiment was carried out in two seasons using a set of 9 recent German winter wheat cultivars (among them a hybrid cultivar and its parent lines). Beneath combine harvest, sequential harvests by hand were conducted (4 in the growing season 2013–2014, 5 in the growing season 2014–2015) to ascertain the above-ground biomass, the leaf area index and the harvest index (at the final harvest). Non-destructive measurements with a plant canopy analyzer to measure leaf area indices and mean tilt angles were conducted 4 times in 2014 and 9 times in 2015. Light absorption was calculated based on interpolated values of leaf area indices and mean tilt angles. Light use efficiency was calculated based on the linear relationship between above-ground biomasses at hand harvests and the related quantities of absorbed radiation. For all parameters of yield formation besides light use efficiency ( P = 0.073) statistically significant differences regarding the cultivars can be observed. Our results suggest that grain yield of modern German cultivars can be explained to a similar extent by differences in harvest indices (adj. r 2 : 0.77) and total biomass accumulation (adj. r 2 : 0.61). Variation in biomass accumulation partly can be explained by light use efficiency differences and to a lesser extent by differences in radiation interception. Most of the differences in biomass accumulation result, however, from differences in the accumulation of biomass from mid flowering to the final yield which for methodological reasons could not be further dissected to effects of light use efficiency and radiation interception. This information gap was described by the introduced parameter late performance. Various combinations of high and low performance, regarding the parameters of yield formation, exist in the analyzed set of cultivars.

Distribución de biomasa aérea en un bosque de Pinus patula bajo gestión forestal en Zacualtipán, Hidalgo, México

La acumulación y distribución de biomasa hacia los componentes estructurales de los árboles es determinante en bosques manejados, tanto en términos de productividad maderable como en la reactivación de diversos procesos ecosistémicos. En el presente estudio se analizó el patrón de acumulación de biomasa aérea total (BAT) y su asignación hacia fuste, ramas, corteza y follaje en una cronosecuencia de un bosque de Pinus patula bajo aprovechamiento forestal en Zacualtipán, Hidalgo. Mediante el uso de ecuaciones alométricas se estimó la BAT y por componente estructural de los árboles en rodales con diferentes años después de la cosecha, en diferentes años de remedición (años 2005, 2008 y 2012). Se encontró que la BAT aumentó con el tiempo después de la cosecha, con diferencias estadísticas significativas (p < 0.0001) entre los rodales. El rodal de 30 años después de la cosecha presentó una biomasa aérea total (BAT) de 178.1 Mg ha-1, la cual resultó solo 20% menor a la observada en el rodal sin cosecha (AN), lo que indica que un bosque bajo aprovechamiento podría alcanzar niveles de biomasa aérea similares a la del AN, en un menor tiempo. La asignación de biomasa aérea (BA) presentó el siguiente orden: fuste> ramas> corteza> follaje. Esta asignación de BA fue favorecida hacia fuste como un producto maderable comercial, objetivo principal de estos bosques bajo producción. El patrón de asignación de BA entre los componentes estructurales de los árboles puede ser incorporado como base para el diseño de prácticas silvicuturales en los programas de manejo forestal y contribuir en la evaluación de la sustentabilidad de los bosques. Además, puede clarificar el papel de los bosques regenerados después de los aprovechamientos en la fijación y almacenamiento de bióxido de carbono atmosférico.

Biomass, carbon storage and nutrient characteristics in Larix kaempferi plantations at diffe-rent stand ages

Based on 7-, 17-, 30-, and 40-year-old Larix kaempferi plantations, this paper studied the influence of tree age on biomass, carbon storage and nutrient characteristics. There was significant difference in biomass and nutrient concentration of stem, bark, needle, branch and root at different development stages at individual tree level. The biomass of each organ showed a trend of increase with the increasing age. The concentrations of N, P, K decreased, Mg concentration increased at first and then decreased, and Ca concentration continued to rise with the increasing age. There was significant difference in biomass of each organ for dominant, intermediate and suppressed trees, but no significant difference in nutrient concentration. It indicated that nutrient concentration of each organ was not affected by competition. At stand level, the total biomass, carbon storage and nutrient accumulation increased with the increasing age. Compared with young stand, the growth rate of biomass, carbon storage and nutrient accumulation were increased by 217%, 218% and 56% in mature stand, respectively. It indicated L. kaempferi had a high nutrient use efficiency, and could utilize less nutrient to produce more dry matter. Except that the accumulation of P and K had a slight decrease in pre-mature stand (30 years old), other elements increased with the increasing age. N mainly concentrated in needle, Ca concentrated in stem, K and Mg concentrated in root and P was distributed evenly in different organs. The annual accumulation rates of biomass, carbon and nutrient of L. kaempferi stands decreased with the increasing age, from 7.16 t·hm-2, 3.40 t·hm-2 and 104.64 kg·hm-2 for young stand to 3.99 t·hm-2, 1.89 t·hm-2and 28.64 kg·hm-2 for mature stand, respectively. It indicated that L. kaempferi plantations had great carbon sequestration potential and high nutrient consumption during young and middle ages.

Carbon sequestration and substitution potential of subtropical mountain Sugi plantation forests in central Taiwan

Forests are the most important terrestrial carbon source and sink, with forest biomass and productivity influencing the level of carbon storage in the ecosystem. In this study, the carbon sequestration of Sugi (Japanese cedar) was estimated according to 25-year plantation forest inventory data in the Experimental Forest, National Taiwan University, Nantou County, Taiwan. The total biomass, trunk biomass, and shoot biomass were used to calculate the carbon sequestration potential of Sugi plantation forests for 8995 acres. Additionally, the potential for bioethanol production from the shoot biomass was also estimated after 25 years of plantation. The results show that the total aboveground biomass accumulation is 935,231 m3, with an average areal biomass accumulation of 838.17 m3/ha. Total trunk volume is tallied at 562,274 m3, with stem volume accumulation at 243,285 m3/ha. Carbon sequestration is estimated at 274,571 tons. Shoot biomass could be converted to 58,194 tons of bioethanol. Substitution of steel and aluminum by overall Sugi trunk volume could reduce CO2 emissions by 72,9498 and 4,994,253 tons, respectively. Compared with other building materials, the consumption of wood board is relatively low. The greater use of wood products as building materials could thus reduce greenhouse gas emissions and have a lower environmental loading than other building materials. The long-term carbon sequestration and substitution potential of subtropical mountain Sugi plantation forests are identified by this study for the first time.

Moderate drought did not affect the effectiveness of ethylenediurea (EDU) in protecting Populus cathayana from ambient ozone

A field study was conducted to evaluate the effects of ambient ozone (O3) on an O3-sensitive poplar (Populus cathayana) by using ethylenediurea (EDU) as a chemical protectant under two soil water treatments (well-watered (WW) and moderate drought (MD, 50–60% of WW in volumetric soil water content). EDU was applied as foliar spray at 0, 300, 450, and 600ppm. Photosynthetic parameters, pigment contents, leaf nitrogen, antioxidant capacity, growth, and biomass were measured. The 8h (9:00–17:00) average ambient O3 concentration was 71.7ppb, and AOT40 was 29.2ppmh during the experimental period (9 June to 21 September), which was high enough to cause plant injury. MD had significantly negative effects on P. cathayana, as indicated by reduced photosynthesis, growth, and biomass, and higher MDA contents. On the other hand, EDU significantly increased photosynthesis rate, chlorophyll a fluorescence, Vcmax and Jmax, photosynthetic pigments, total antioxidant capacity, tree growth and biomass accumulation, and reduced lipid peroxidation, but there was no significant interaction between EDU and drought for most parameters, indicating that EDU can efficiently protect Populus cathayana against ambient O3 and the protection was not affected by soil water contents when soil water reached moderate drought level. Among all doses, EDU at 450ppm provided maximum protection. Comparison of EDU-treated and non-treated P. cathayana could be used as a biomarker system in risk assessment of the effects of ambient O3 on forest health.

Diurnal temperature amplitude alters physiological and growth response of maize (Zea mays L.) during the vegetative stage

Global climate models predict increase in mean daily temperature to be mainly driven by rapid increase in nighttime temperature compared to daytime temperature, leading to narrowing diurnal temperature amplitude. Higher day and night temperatures induce significant negative impact on growth and development of different crops. However, limited studies have focused on quantifying impacts associated with different diurnal temperature amplitudes maintaining the same daily mean temperature. The main objectives were to (i) quantify the impact of diurnal temperature amplitudes on the carbon balance of the plant (photosynthesis versus night respiration rate) and (ii) evaluate the significance of variable day and night temperature with a common mean on the carbohydrate composition and overall plant growth. A maize hybrid (DKC47-27RIB) was grown in controlled environments at two mean daily temperatures (30°C and 35°C) with three different combinations of day and night temperatures resulting in diurnal temperature amplitudes of 2°C, 10°C and 18°C. After 42days of temperature treatments, lower diurnal temperature amplitude led to a linear increase in night respiration and a linear decrease in total sugars, non-reducing sugars, starch concentrations, plant height, total leaf area and total biomass accumulation. However, there was no significant change in photosynthetic rate among the treatment combinations, while photochemical efficiency (Fv/Fm) and chlorophyll index decreased only with diurnal temperature amplitude of 18°C and 2°C, respectively. A significant negative relationship was found between night respiration and total biomass accumulation (R2=0.73; P<0.01), total leaf area (R2=0.82; P<0.01), specific leaf area (R2=0.21; P<0.01), non-reducing sugars (R2=0.50; P<0.01) and starch concentrations (R2=0.50; P<0.01). The results imply that narrowing diurnal temperature amplitude as a result of higher night temperature is the major driver of the negative impact on vegetative growth in maize.

The legacy of disturbance on individual tree and stand-level aboveground biomass accumulation and stocks in primary mountain Picea abies forests

Disturbances, both natural and human induced, influence forest dynamics, ecosystem functioning, and ecosystem services. Here, we aim to evaluate the consequences of natural disturbances on the magnitude and dynamics of tree- and stand-level biomass accumulation from decadal to centennial scales. We use tree-ring data from 2301 trees and biometric data from 4909 trees sampled in 96 plots (each 1000m2) to quantify the influence of mixed severity disturbance regimes on annual aboveground biomass increment (AGBI) and total aboveground biomass accumulation (AGB) across a mountainous monotypic Norway spruce (Picea abies (L.) Karst.) primary forest. We hypothesise that the multiple internal and external factors constraining tree growth will cause differences in tree and stand-level biomass trajectories in these natural forests.Although we found that tree-level AGB growth increases with tree size, we also found that tree age and disturbance legacies plays a crucial role for AGB in the investigated Norway spruce forests. Importantly, while younger trees of the same diameter class have an average current AGBI rate that is ∼225% higher than older trees (300–400years), we find trees that have been suppressed for up to 120years can respond vigorously when competition is reduced. On average, post disturbance AGBI was ∼400% greater than pre-disturbance AGBI. Growth of suppressed trees, independent of their age, followed similar trajectories after canopy accession. While aboveground biomass generally increased through time, the time since disturbance and disturbance severity are important co-predictors for stand-level AGBI and AGB. These forests regained most of the above ground living biomass over short interval (∼50years) after low intensity disturbances. The highest stand-level living AGB was observed on plots that experienced >40% canopy removal 160–190years ago, whereas the highest AGBI occurred in plots disturbed recently within the past 40–50years.Our results emphasize the importance of including both individual tree age and disturbance legacies to accurately characterize biomass dynamics and trajectories in forest ecosystems. Importantly, the period of time that a tree is in the canopy, and not tree age, modulates the trajectory of tree level AGBI. Growth rates begin to decline after ∼30years (tree-rings width) and ∼100years (AGBI) in the canopy. We demonstrate that even late-seral forests can rapidly regain biomass lost to low intensity disturbance.

Application of municipal biowaste derived products in Hibiscus cultivation: Effect on leaf gaseous exchange activity, and plant biomass accumulation and quality

Two urban biowaste materials, fermented under anaerobic and aerobic conditions, their soluble and insoluble alkaline hydrolysates, and a commercial biostimulant product, were compared for their capacity to boost Hibiscus crop production and quality. Plants were grown in 4‐litre pots, containing peat and pumice as substrate, under optimal growing conditions. A randomized-block experimental design was adopted. Two types (main factors of variability) of treatments were applied, i.e. by blending the above products with the substrate at transplant, and by fertigation using the soluble hydrolysates only. Plant biomass characteristics and ecophysiological parameters were measured. Mean effect of factors and their interactions were assessed by two‐way ANOVA. Principal component analysis was performed by using the different dependent variables to summarize the most relevant differences among treatments. Compared with the control (untreated plants), the applied treatments enhanced most of the investigated parameters. The most valuable effects were observed for total biomass accumulation (+25%), plant height (+10%), leaf chlorophyll SPAD index (+15%) and net photosynthesis (+24%). The hydrolysates performed better than the pristine materials. The former ones were comparable to the commercial biostimulant. The results confirmed the hypothesis that biowaste derived products induce biostimulant activity on Hibiscus; their application can improve cultivation sustainability.

Assessment of biomass recovery and soil carbon storage of fallow forests after swidden cultivation in the Bago Mountains, Myanmar

The role of swidden fallows in carbon storage is poorly understood, especially in Myanmar, due to the complex and dynamic characteristics of fallows and limited available data. We studied fallow forests formed as a consequence of Karen swiddeners in the Bago Mountains, Myanmar, assessing above- and belowground biomass recovery and soil carbon storage in fallow forests using a chronosequence approach. The accumulated total biomass was 12.13–356.95 Mg ha−1, the accumulated carbon stock was 5.70–167.77 Mg C ha−1, and the soil carbon stock was 5.70–167.77 Mg C ha−1 in the fallow forests. Our analysis suggested that the fallow forests in this study should recover to the total biomass accumulation of old forests after 20–35 years. We established a curve of total biomass accumulation in the fallows against age that can be easily used when the age of the fallows is known. Based on soil carbon analysis, total carbon storage fluctuated with fallow age and decreased with soil depth. The overall soil carbon accumulation in fallow forest soil was 43.63–70.11 Mg ha−1. This study contributes to the understanding of fallow forest and swidden agricultural system carbon stocks and can be used for planning future agreements, such as Reducing Emissions from deforestation and forest degradation in developing countries (REDD+), at national and regional levels.

Growth and competitive abilities of the federally endangered Lindera melissifolia and the potentially invasive Brunnichia ovata in varying densities, hydrologic regimes, and light availabilities

Brunnichia ovata (Walter) Shinners is a native, perennial, woody vine with the potential to become an aggressive competitor of the federally endangered shrub Lindera melissifolia (Walt.) Blume. Our study simulated habitat disturbances to hydrologic regime and light availability that may occur naturally, or through active management practices aimed at ensuring the sustainability of L. melissifolia, and we determined the species responses to these changes. First-year plants of L. melissifolia and B. ovata were grown at varying densities, in flooding or nonflooding treatments, and receiving 100%, 47%, or 21% light availabilities. For both species, density effects, in combination with light availability and flooding regime influenced total biomass accumulation. Brunnichia ovata exhibited a high degree of plasticity with respect to biomass allocated between above- and below-ground tissues in response to flooding, whereas biomass allocation in L. melissifolia was relatively unaffected. Interspecific competition occurred primarily in nonflooding treatments. Our study highlighted the complexity of the relationship of L. melissifolia and B. ovata with regard to functional trait responses to changes in abiotic and biotic factors, and indicated that it will be necessary to consider entire plant community responses to mitigate increased competitive interactions and ensure the survival of L. melissifolia populations.

Planting date and in-row plant spacing effects on growth and yield of cabbage under plastic mulch

Florida is ranked third in total cabbage production in the U.S. and it is traditionally grown on bare ground with subirrigation. The use of plastic mulch and drip irrigation is widespread for other vegetable crops and can enhance water and fertilizer use efficiency and yield. The objective of the study was to evaluate plant growth, yield and head quality traits of cabbage using three plant populations and four planting dates on a plastic mulch system. Cabbage was transplanted in mid September (SEP), mid October (OCT), early November (NOV), and early December (DEC) in the 2013–14 and 2014–15 growing seasons, spanning the entire planting season for commercial operations in northeast Florida. There was no interaction among planting dates and plant populations for total and marketable yields or biomass. For both seasons, the SEP and OCT plantings showed a faster growth rate than NOV and DEC during the first 70 days after transplanting; however, differences in total biomass accumulation were only seen in 2013–14. Biomass decreased quadratically in 2013–14 with an increase in in-row spacing. Average marketable yield for both years was 62.7, 60.5, 46.2, and 58.6Mgha−1 for SEP, OCT, NOV and DEC, respectively. As plant population decreased, marketable yield increased linearly in 2013–14 while no differences were seen in marketable yield among plant population treatments during 2014–15 season. Plant growth rate and yield were correlated to growing season average air temperature and solar radiation. The SEP, OCT and DEC planting dates benefited from more favorable weather conditions, while low air temperatures and reduced solar radiation had a negative effected on cabbage yield for the NOV planting.

Optimum harvest time of Tulipa edulis based on comparison of biomass accumulation and medicinal quality evaluation

The optimum harvest time of Tulipa edulis was explored based on biomass accumulation and medicinal quality evaluation. Samples were taken from bud stage (Feb 13th) to dormancy stage (May 14th) and the growth indexes, organs biomasses, drying rate, contents of water-soluble extract and polysaccharides were determined. The results showed that biomass distribution of T. edulis varied with growth center and the bulb gained maximum biomass allocation in the whole growth period. The total biomass accumulation and bulb biomass accumulation increased in the whole growth period and peaked in fructescence stage. No differences were observed in bulb biomass among fructescence stage, withering stage and dormancy stage. The correlation between bulb biomass allocation and other morphological indexes varied with the harvest time. Bulb dry weight biomass had negative correlation with some morphological indexes of aerial part of T. edulis at bud stage, flower stage and fructescence and had significant positive (P<0.05) or extremely significant positive correlation（P<0.01）with other morphological indexes except for root at bearing fruits stage. The drying rate of bulb of T. edulis increased with the extension of harvest time and peaked in dormancy stage. The water-soluble extract of T. edulis bulb was the highest in pre-growing-stage. The tendency of polysaccharides contents showed a W-shape variation during the harvesting period. The polysaccharides content was the lowest in fructescence stage and was the highest in dormancy stage. Considering the yield and medicinal quality of T. edulis bulb, the optimum harvest time of T. edulis is in the withering stage or early stage of dormancy.

Nitrogen and phosphorus removal from tertiary wastewater in an osmotic membrane photobioreactor

An osmotic membrane photobioreactor (OMPBR) was designed and operated for 162days for nitrogen and phosphorus removal from wastewater using Chlorella vulgaris. The removal efficiency for NH4+-N, NO3−-N and PO43−-P reached as high as 95%, 53% and 89%, whereas the maximum removal rates were 3.41mg/L-day, 0.20mg/L-day and 0.8mg/L-day, respectively. The microalgae exhibited high tendency to aggregate and attached to the bioreactor and membrane surfaces, and total biomass accumulation in the OMPBR was over 5g/L. Salt accumulation and biofouling had adverse effects on membrane filtration, but the performance could be recovered through periodic backwashing of the membranes. Extracellular polymeric substances characterization indicated higher fraction of polysaccharides as compared to proteins. The biomass in the OMPBR accumulated higher levels of carbohydrates and chlorophyll. These results indicate the suitability of OMPBR in wastewater treatment and in high-density microalgae cultivation.

Weed Management, Training, and Irrigation Practices for Organic Production of Trailing Blackberry: III. Accumulation and Removal of Aboveground Biomass, Carbon, and Nutrients

Relatively little is known about aboveground nutrient content of organic blackberry, and there is no published work on total carbon (C) content. Treatment effects on biomass, C, and nutrient content, accumulation, and removal were assessed over 2 years in a mature organic trailing blackberry (Rubus L. subgenus Rubus, Watson) production system that was machine harvested for the processed market. Treatments included two irrigation options (no irrigation after harvest and continuous summer irrigation), three weed management strategies (weed mat, hand-weeded, and nonweeded), and two primocane training times (August and February) in two cultivars (Black Diamond and Marion). Floricanes comprised an average of 45% of the total aboveground plant dry biomass, while primocanes and fruit comprised 30% and 25%, respectively. Depending on the treatment, the total aboveground dry biomass accumulation over the course of the season was 5.0–6.5 t·ha−1 per year, while C stock of the planting was an estimated 0.4–1.1 t·ha−1 in late winter. Carbon accounted for ≈50% of the dry biomass of each aboveground plant part, including primocanes, floricanes, and fruit. Weed management had the largest impact on plant biomass and nutrient content. No weed control reduced aboveground dry biomass, the content of nutrients in the primocanes, floricanes, and fruit, and the annual accumulation of dry biomass and nutrients, whereas use of weed mat resulted in the most dry biomass and nutrient content. Nutrient accumulation was similar between the cultivars, although February-trained ‘Marion’ plants had a greater removal of most nutrients in 2014 than the year prior. The amount of nitrogen (N) removed in the fruit was 22, 18, and 12 kg·ha−1 for weed mat, hand-weeded, and nonweeded plots, respectively, in 2013. In 2014, ‘Marion’ and ‘Black Diamond’ differed in N removed in harvested fruit when grown with weed mat at 18 and 24 kg·ha−1, respectively, whereas there was no cultivar effect when plants were grown in hand-weeded or nonweeded plots. Plots with weed mat tended to have the most nutrients removed through harvested fruit in both years. In 2014, N removal from August-trained ‘Marion’ was 5 kg·ha−1 N less than the other training time and cultivar combinations. Plants that were irrigated throughout the summer accumulated more dry biomass, N, potassium (K), magnesium (Mg), sulfur (S), boron (B), and copper in one or both years than those that received no irrigation after fruit harvest. The irrigation treatment had inconsistent effects on nutrient content of each individual plant part between the two years. Removal of nutrients was often higher than what was applied through fertilization, especially for N, K, and B, which would eventually lead to depletion of those nutrients in the planting.

Impact of autumn (fall) dormancy rating on growth and development of seedling lucerne

To quantify the influence of autumn (fall) dormancy (FD) on DM production and phenological development during the seedling phase, three lucerne genotypes with contrasting ratings were grown at Lincoln University, New Zealand. A dormant (FD2), a semi-dormant (FD5), and a winter-active (FD10) genotype were inoculated and sown at a rate of 290 plants/m2 on 8 October 2014. By the end of the seedling phase (15 January 2015) the FD10 genotype had produced 20% higher shoot yield and 17% higher root yield than the other two genotypes. The percentage of total biomass partitioned to roots (Proot) was 50% for all genotypes. Total plant biomass (root + shoot yields) was 6.55 t DM/ha for FD10 compared with 5.57 t DM/ha for FD 2 and FD5. Plant height at the open-flower stage was 39.5 cm for FD10 compared with 34.5 cm for FD5 and 33.5 cm for FD2. Maximum leaf area index was similar amongst genotypes at 2.5. However, individual leaf area was 142, 119 and 111 cm2/stem for FD10, FD5 and FD2, respectively. The phyllochron was 52oCd per primary leaf (base temperature of 1oC) and consistent amongst genotypes. The number of primary leaves and branches were also conservative at 17 and 14/shoot, respectively. Therefore, differences in shoot yield among these lucerne genotypes during the seedling stage were mainly due to differences in plant height and individual leaf area expansion per plant. This led to greater light interception and therefore higher total biomass accumulation for FD10 than for the other two genotypes. Keywords: alfalfa, autumn, Medicago sativa L., phyllochron

Características fisiológicas do feijoeiro cultivado em solos após fitorremediação do picloram

A fitorremediação tem sido relatada como técnica promissora para a descontaminação de solos com resíduos de herbicidas. Para herbicidas hormonais, há dificuldade na determinação de resíduos pela técnica do bioensaio em função da variação na resposta em crescimento apresentada pela indicadora. Objetivou-se com esse trabalho avaliar o efeito de subdoses do picloram, em solos fitorremediados com braquiária, nas características fisiológicas do feijoeiro. O ensaio foi realizado em ambiente protegido no delineamento de blocos ao acaso. Aplicou-se diferentes doses do picloram (0; 2; 4; 8; 16 e 32 g ha-1), sendo posteriormente cultivado com braquiária por 120 dias. Nesta data retirou-se a braquiária dos vasos e semeou o feijão como planta bioindicadora, sendo depois de 30 dias avaliada as características fisiológicas e a matéria seca do feijoeiro. Mesmo após a remediação por plantas de braquiária, as subdoses do picloram afetaram as características fisiológicas do feijoeiro, principalmente a taxa fotossintética e a eficiência no uso da água, sendo essas variáveis as mais indicadas para se avaliar o resíduo do herbicida no solo. A redução dessas variáveis promoveu menor acúmulo de biomassa total das plantas de feijão nos solos fitorremediados. A segunda maior dose do herbicida provocou também redução da relação Fv/Fm abaixo de 0,75, indicando algum tipo de estresse do aparato fotossintético das folhas do feijoeiro.

Influence of UV exclusion and selenium on carbon fixation, nitrogen fixation and yield of soybean variety JS-335

Ultraviolet-B (UV-B) is a significant abiotic stress factor exerting multiple effects on plant growth. This study was undertaken to unravel if selenium (Se), an element known to increase the stress tolerance, is able to defend soybean plants against detrimental effects of ambient UV. Soybean plants were grown in soil supplemented with Se at 0, 0.1 and 1.0mgkg−1 soil under ambient and filtered solar UV. The influence of ambient and filtered solar UV and of Se was determined on growth of above/below-ground parts, biomass accumulation, rate of photosynthesis, protein, nitrate reductase activity, leghemoglobin content and yield in soybean var. JS 335. Both the low and high Se dosage significantly enhanced the growth of above-ground parts (plant height, leaf area and total biomass accumulation) as well as the growth of below-ground parts (root length, root biomass, number of nodules and fresh weight of nodules) as compared to their control (0mgkg−1 soil) plants under ambient and filter control treatments (+UV-B and UV-A). Leghemoglobin content was higher in the root nodules and the total chlorophyll, total soluble protein and NR activity in leaves were also significantly increased by Se as compared to their controls under ambient and filter control treatments. Similarly, exclusion of solar UV radiations also significantly enhanced these parameters except NR activity as compared to the controls. Selenium increased the grain yield of soybean under ambient conditions. The results suggest that the increased yield of soybean by Se and UV exclusion was related to increased carbon and nitrogen fixation which was evident by the increased rate of photosynthesis, higher activity of nitrate reductase and high amount of leghemoglobin in root nodules of soybean. An increase in physiological indices with Se supply confirmed that Se plays a positive role in improving UV (280–400nm) tolerance of soybean seedlings. A comparison of results of growing plants in supplementation of Se in soil under ambient UV and without Se supplementation in soil under solar UV exclusion indicates a parallelism between the two effects. Both enhanced the growth of the plants and accumulation of biomass, hence enhanced fixation of carbon and nitrogen, ultimately enhanced the crop yield. Thus Se supply significantly increased the growth and yield of soybean under ambient UV stress.

The effect of over-expression of rate limiting enzymes on the yield of artemisinin in Artemisia annua

Medicinal plants are rich source of bioactive compounds which are important for human healthcare. The production of bioactive compounds such as artemisinin is limited in plants. Novel antimalarial drug artemisinin was obtained from leaves of Artemisia annua L. plants. The content of artemisinin in the natural plant is 0.01–1.1 % on dry weight basis. Due to its low content, the drug could not be commercialized in the global market to explore the artemisinin-based combined therapies in the world. The economic limitations of chemical synthesis is unfeasible due to its complexity and cost effectiveness. In this article, we have studied the effect of rate limiting enzymes/genes expression, HMG-Co A reductase and amorpha-4,11-diene synthase on physiochemical changes in terms of total biomass, chlorophyll, total protein, artemisinin content and yield in transgenic lines of A. annua L. plants. The shoot length (42.00 %), number of leaves (86.89 %), the number of root (39.82 %) root length (83.61 %), total biomass accumulation (100 %), total chlorophyll level (138.14 %), total protein level (73.36 %) in TR4 at in vitro level while artemisinin (93.54 %) and its yield (237.26 %) were maximum in TR5 at polyhouse conditions, followed by TR1, TR2, TR3, TR7 and TR9 as compared to non-transgenic Artemisia annua L. plants. A similar trend in leaf biomass, stem biomass and leaf:stem ratio was also recorded in polyhouse condition.

Interaction between plant density and nitrogen management strategy in improving maize grain yield and nitrogen use efficiency on the North China Plain

SUMMARYUnderstanding the physiological mechanisms of biomass accumulation and partitioning in the grain, and the nitrogen (N) uptake associated with different plant densities and N management strategies, is essential for achieving both high yield and N use efficiency (NUE) in maize plants. A field experiment was conducted in 2013 and 2014, using five rates of N application and three plant densities (6·0, 7·5 and 9·0 plants/m2) in Quzhou County on the North China Plain (NCP). The objective was to evaluate whether higher plant density can produce more biomass allocated to the grain to achieve higher grain yield and to determine the optimal N management strategies for different plant densities. The highest grain yield and NUE were achieved in the 7·5 plants/m2 treatment; both the sub-optimal (6·0 plants/m2) and supra-optimal (9·0 plants/m2) plant densities resulted in diminished yield and NUE. Compared to 6·0 plants/m2, the 7·5 plants/m2 treatment displayed higher biomass accumulation during the grain-filling period and also exhibited more biomass allocated to kernels with similar total biomass accumulation compared with the 9·0 plants/m2 treatment, which contributed to its higher grain yield. The N uptake in the 7·5 plants/m2 treatment was similar to that in the 9·0 plants/m2 treatment up to pre-silking. However, the post-silking N uptake of the 7·5 plants/m2 treatment was 66·4 kg/ha, which was 29·1% higher than that of the 9·0 plants/m2 treatment. Furthermore, the highest maize grain yield was achieved in the 0·7 × optimal N rate (ONR × 0·7), ONR and ONR × 1·3 treatments for 6·0, 7·5 and 9·0 plants/m2, respectively, which suggests that different N management strategies are needed for different plant densities. In conclusion, selecting a planting density of 7·5 plants/m2 with an in-season root zone N management is a potentially effective strategy for achieving high grain yield and high NUE for maize production on the NCP.