Shoot Biomass Accumulation Research Articles

Wood production and nutritional and antioxidant status of field-grown Eucalyptus under a differential supply of lime and copper plus zinc

The Eucalyptus grandis L. plantations for industrial purposes (e.g., wood charcoal and pulp) are largely adopted worldwide, mainly in acidic and poorly fertile soils. The application of lime to soil is recommended for eucalyptus plantation, but lime reduces the availability of metallic micronutrients to plants. Therefore, the aim of this study was to investigate the performance of field-grown Eucalyptus grandis in Ferralsol amended with lime at different rates (0.0 and 1.6 and 3.7 Mg ha-1) and Cu plus Zn [0.0 and 0.0 kg ha-1 (-CuZn) and 0.5 and 1.5 kg ha-1 (+CuZn)]. The soil chemical attributes, shoot biomass, and nutrient accumulation were evaluated, while nutrient use efficiency, chlorophyll (Chl) and flavonoid (Flav) contents, and enzymatic antioxidant performance [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX), guaiacol peroxidase (GPOX), and glutathione peroxidase (GPX)] were assayed to assess the nutritional status of the plants. Despite the lime application rate increasing Ca and Mg soil availabilities, effective cation exchange capacity (eCEC), base saturation (BS), and pH values, the available Cu, Fe, and Zn concentrations decreased at 6 and 30 months after planting. Conversely, Mn soil availability increased with lime application rates. Liming augmented Cu-, Fe-, Mn-, and Zn-use efficiency, while +CuZn supply increased enzymatic antioxidant performance in 30-month-old plant. Overall, the combined application of lime and +CuZn enhanced shoot biomass relative to that of non-treated plants. However, there was no observed difference in shoot biomass in 30-month-old limed and non-limed eucalyptus trees that were supplied with +CuZn. This result can be partially explained by the improvement in soil chemical attributes, such as soil pH, eCEC, and BS. In conclusion, the use of integrative approaches and temporal evaluations provided new insights into wood yield, biochemical traits, antioxidant metabolism, and the nutritional status of field-grown eucalyptus under lime and +CuZn application rates.

Cryptochrome 1a of tomato modulates nutritional deficiency responses

The blue light photoreceptor cryptochromes are involved in nutritional response pathways in plants. Evidence shows that cryptochromes mediate the control of genes related to nutrients accumulation in plants. However, nothing is known about the role of cryptochrome 1a (cry1a) in tomato (Solanum lycopersicum L.) nutritional stress responses. Thus, this study aims to evaluate the importance of cry1a photoreceptors in plant responses to nutrient deficiency. To this end, we proposed the use of a tomato mutant carrying a lesion in a gene encoding the blue light photoreceptor cry1a (cry1a) and its wild type (WT; cv. Moneymaker). Both genotypes (20-day-old plants) were grown under treatments consisting of a complete nutrient solution and the individual omission of each nutrient (–N, –P, –K, –Ca, or –S) from a balanced nutrient solution. Subsequently, we measured the growth, pigmentation, oxidative stress, and nutrient accumulation, as well as uptake efficiency, transport efficiency, and use efficiency of nutrients in all treated plants. The cry1a plants had greater shoot extension growth than WT plants in all tested growth conditions, although the shoot biomass accumulation with cry1a was greater than in the WT only under Ca omission. Except in the –N and –Ca conditions, the cry1a plants accumulated less root biomass than WT plants. In addition, leaf pigments (chlorophyll a+b and carotenoids) were reduced in the mutant plants compared to WT plants grown under CS, –P, and –S conditions. Thus, considering that WT plants have the full functions of cry1a photoreceptor, here we showed that cry1a plays an important role in the nutrient deficiency responses in tomato, particularly, mediating growth and development of stressed plants through changes in plant growth and oxidative stress, as well as the nutrient contents and efficiencies of transport use.

Growth, foliar gas exchange and biomass accumulation in passion fruit seedlings irrigated with saline waters and due to the applications of salt stress attenuators

The use of substances attenuating the harmful effects of salts on plants is an important strategy for the use of salt water in agriculture. The objective of this work was to evaluate the growth, gas exchange and biomass accumulation of passion fruit seedlings (Passiflora edulis Sims) irrigated with salt water due to the application of salt stress attenuators. The experiment was carried out in a randomized complete block design, in a 5 x 3 x 2 factorial scheme, with three replications, referring to the electrical conductivities of the irrigation water (1.5, 2.5, 3.5, 4.5 and 5.5 dS m-1), three doses of humic acids (0, 10 and 20 mL) and two doses of citric acid (0 and 10 mL) as attenuators, respectively. Increased salinity of irrigation water reduced growth, accumulation of dry shoot biomass and gas exchange (stomatal conductance, transpiration, net photosynthesis, CO2 internal concentration) of passion fruit sourced seedlings. Citric acid did not attenuate the negative effects of the salts and negatively interfered in the growth and accumulation of dry biomass of the shoots of passion fruit, mainly to the seedlings irrigated with water of low salinity. Humic substances at a dose of 20 mL promoted higher growth of passion fruit sprouts but were not sufficient to attenuate the negative effects of irrigation water salts. Therefore, citric acid and humic substances, under the conditions of the study, are not an option to use saline water in the production of passion fruit seedlings

Arbuscular Mycorrhizal Fungi Increase Pb Uptake of Colonized and Non-Colonized Medicago truncatula Root and Deliver Extra Pb to Colonized Root Segment.

Arbuscular mycorrhizal (AM) fungi establish symbiosis and improve the lead (Pb) tolerance of host plants. The AM plants accumulate more Pb in roots than their non-mycorrhizal counterparts. However, the direct and long-term impact of AM fungi on plant Pb uptake has been rarely reported. In this study, AM fungus (Rhizophagus irregularis) colonized and non-colonized roots of Medicago truncatula were separated by a split-root system, and their differences in responding to Pb application were compared. The shoot biomass accumulation and transpiration were increased after R. irregularis inoculation, whereas the biomass of both colonized and non-colonized roots was decreased. Lead application in the non-colonized root compartment increased the R. irregularis colonization rate and up-regulated the relative expressions of MtPT4 and MtBCP1 in the colonized root compartments. Rhizophagus irregularis inoculation increased Pb uptake in both colonized and non-colonized roots, and R. irregularis transferred Pb to the colonized root segment. The Pb transferred through the colonized root segment had low mobility and might be sequestrated and compartmented in the root by R. irregularis. The Pb uptake of roots might follow water flow, which is facilitated by MtPIP2. The quantification of Pb transfer via the mycorrhizal pathway and the involvement of MtPIP2 deserve further study.

Altering maize (Zea mays) seedlings’ growth and lignification processes by action of novel synthesized compounds

Effective management of the course of crop vegetation and adaptation to biotic and abiotic stresses is a prerequisite for stable grain production and requires replenishment of the arsenal of plant growth regulators. The effect of novel synthesized cage amides on maize seedlings morphogenesis has been tested. Seeds of a mid-early maize hybrid 'DN Galatea' after the pre-sowing treatment with 0.01% solutions of test compounds were grown in distilled water. The roots and shoots sections of 10-day-old maize seedlings were stained with phloroglucinol solution to reveal the lignin-containing anatomical structures. The effects of nine different test compounds, exceeding the well-known effects of the phytohormone auxin, promoted the maize seedlings’ linear growth, increased wet weight of roots and shoots, and dry biomass accumulation both in seedlings roots and shoots. Several test compounds activated the dry weight accumulation process without significantly affecting the root and shoot length. In the maize seedlings’ roots, an increase in the diameter and number of the xylem vessels was found, as well as an increase in the lignin-containing layer thickness of the endoderm cells in the root cortex. In the maize seedlings’ shoots, the test compounds caused an increase in the thickness of the lignin-containing outer layer of the seedlings’ first leaf. In general, the test compounds’ effect on seedling roots can potentially enhance root formation; increase efficiency of the roots water-conducting system and the tissues’ strength, thus reducing the likelihood of root lodging in maize plants. The effects of the test compounds revealed in the seedlings’ shoots reflect the activation of the shoots’ structure formation and may have a positive value for enhancing the strength of the plant stems and counteracting the stem lodging of the maize plants.

Influence of cadmium-resistant Streptomycetes on plant growth and cadmium uptake by Chlorophytum comosum (Thunb.) Jacques.

This work aims to explore the role of cadmium-resistant actinomycetes on promoting plant growth and cadmium uptake in Chlorophytum comosum (Thunb.) Jacques, a spider plant. Actinomycetes isolated from the plant roots in peat swamp forests were screened for their cadmium resistance and the production of indole-3-acetic acid (IAA) and siderophores. The results found that K5PN1 and 11-10SHTh produced high levels of IAA and siderophores, respectively. K5PN1 and 11-10SHTh were identified to be Streptomyces rapamycinicus and Streptomyces cyaneus, respectively. Both strains were able to remove cadmium from aqueous solution and survive under cadmium stress in contaminated soil. The results of pot experiments found that the selected Streptomyces inoculation increased the root and shoot biomass and cadmium accumulation in the root and shoot of C. comosum planted in a cadmium-contaminated soil. The highest cadmium accumulation and translocation ability of cadmium from the root to shoot was found in C. comosum with S. rapamycinicus inoculation. In addition, plant with S. cyaneus inoculation had the highest phytoextraction coefficient and bioaccumulation factor. Our findings concluded that S. rapamycinicus and S. cyaneus stimulated the growth and cadmium uptake in C. comosum, suggesting a combined approach using the selected Streptomyces and C. comosum for phytoremediation of cadmium-polluted soil.

Critical plant phosphorus for winter wheat assessed from long-term field experiments

Optimizing the use of phosphorus (P) fertilizers is essential considering the environmental issues linked to over fertilization and the limited rock phosphate reserve. Diagnosing the crop P status by calculating a phosphorus nutrition index (PNI) based on the plant critical P concentration (Pc) could help determine the minimum amount of P fertilizer to ensure maximum crop yield. This study investigated (i) the effect of P fertilization on winter wheat (Triticum hybernum L.) shoot biomass and grain yield after several decades of different annual P fertilization rates, (ii) the stability over several site-years of the Pc expressed either as a function of shoot biomass or shoot nitrogen (N) concentration, and (iii) the possibility of using the PNI or the shoot N-to-Pc ratio as nutritional indicators to diagnose P deficiency and predict the expected response to P fertilization. Shoot biomass and its P and N concentrations were measured weekly at five site-years along with grain yield after several decades of P fertilization treatments that ranged between 0 and 5/3 of the theoretical P crop uptake. The P fertilization did not affect the grain yield, but it generally increased shoot biomass especially at the CD 27- -37 developmental stages. The Pc expressed either as a function of shoot biomass or shoot N concentration differed among site-years and this was attributed to differences in crop N status. When N was not deficient, we developed a Pc dilution curve as a function of shoot biomass (SB) (4.56 × SB−0.279) along with a linear relationship (Pc = 1.10 + 0.061 × N) and a power function (Pc = 0.34 × N0.632) between Pc and shoot N concentration. The N-to-Pc ratio was related to shoot biomass accumulation according to a power function, but the relationship also differed among site-years. The relative shoot biomass responded positively to the PNI up to different thresholds for limiting and non-limiting N conditions. The relative grain yield, however, was not related to the PNI. The PNI, based on the Pc dilution curve, has potential as a nutritional indicator to diagnose P deficiency and the expected response to P fertilization, but more research is needed to clarify the effect of N deficiencies on the Pc dilution curve.

How soil ion stress and type influence the flooding adaptive strategies of Phragmites australis and Bolboschoenus planiculmis in temperate saline–alkaline wetlands?

Soil saline–alkaline stress and flooding extremes have been projected to be the main factors influencing the degradation of marsh plants in wetlands worldwide, which would affect their ecological functions (i.e. food source for migrating birds). Plants cope with flooding either by escaping from below water through shoot elongation or by remaining quiescent until water subsides. However, little is known about the adaptive strategies of Phragmites australis and Bolboschoenus planiculmis to flooding combined with salinity–alkalinity, which are the key environmental filters in Western Songnen Plain, China. Accordingly, this study investigated the adaptive strategies of P. australis and B. planiculmis subjected to the interacting effects of flooding and soil ion stress under field and greenhouse conditions. Results showed that the two species adopted different strategies to survive flooding. P. australis exhibited an escape strategy because of leaf and shoot elongation with increasing flooding depth whereas B. planiculmis became quiescent with no or deceased leaf and shoot elongation and biomass accumulation. High soil ion stress changed the flooding adaptive strategy of P. australis to a quiescence strategy, whereas B. planiculmis remained quiescent with increasing flooding depth at each soil ion content. The strategies of the two species were changed by alkaline ion stress but not by saline ion stress, and they exhibited different adaptive responses. High alkaline ion stress induced P. australis to remain quiescent with increasing flooding depth, whereas low alkaline ion stress promoted B. planicumis to escape from below water, probably due to the buffer effect of low alkaline ion contents outside the roots probably. Hence, P. australis and B. planicumis might adopt the quiescence strategy with increasing degree of soil salinization and alkalization under high greenhouse gas emissions scenarios in Western Songnen Plain, which may lead to severe degradation of the two kinds of marshes in the future.

Does Biochar Alleviate Salt Stress Impact on Growth of Salt-Sensitive Crop Common Bean

ABSTRACT This study aimed to evaluate the role of biochar properties and application rate in the alleviation of negative impacts of salinity stress on the growth of salt-sensitive common bean (Phaseolus vulgaris L.). The biochar was obtained by slow pyrolysis of olive pruning at 400°C and characterized as high alkaline (9.3) and having a high cation exchange capacity (CEC) and low electrical conductivity (EC) with high porous surface morphology. Plants were grown in the greenhouse and subjected to different amounts of salt (0, 25, 50 mM NaCl) and biochar rate (0, 5, 15 t/ha). Salinity stress reduced shoot growth, biomass accumulation, total chlorophyll and carotenoid content, these parameters were ameliorated by biochar. Adverse effects of salinity on pod settings were also mitigated by biochar supplements. Salinity triggered oxidative stress monitored by increasing hydrogen peroxide (H2O2) content and cell membrane permeability of leaves were mitigated by only 5 t/ha biochar application in contrast 15 t/ha biochar extended oxidative stress level. Our results showed that biochar application may be a promising strategy to increase common bean growth under saline soils due to its specific physicochemical properties, particularly high Na+ adsorption capacity. However, the higher biochar application rate may augment the adverse effects of soil salinity for salt-sensitive bean growth due to its contribution to the cumulative EC level of the soil.

Carbon Dioxide Concentrations and Light Levels on Growth and Mineral Nutrition of Juvenile Cacao Genotypes

In many countries cacao (Theobroma cacao L.) is invariably grown as an understory crop in agroforestry types of cropping systems and subjected to low levels photosynthetic photon flux density (PPFD) due to presence of large number of upper story shade trees with poorly managed canopy structure. In recent years carbon dioxide concentration in the atmosphere is steadily increasing and it is unclear what impact this will have on performance of cacao grown under shade of upper story shade trees. A climatically controlled greenhouse experiment was undertaken to evaluate the effects of ambient and elevated carbon dioxide (400 and 700 μmol·mol-1) and three levels of PPFD (100, 200, and 400 μmol·m-2·s-1) on growth, and macro- and micronutrient use efficiency of three genetically contrasting cacao genotypes (CCN 51, VB 1117 and NO 81). Intraspecific variations were observed in cacao genotypes for growth parameters at ambient to elevated carbon dioxide and low to adequate levels of PPFD. With the exceptions of total root length and leaf area, irrespective of carbon dioxide and PPFD levels, all three genotypes showed significant differences in all the growth parameters. For all the cacao genotypes, increasing PPFD from 100 to 400 μmol·m-2·s-1 and carbon dioxide from 400 to 700 μmol·mol-1 increased overall growth parameters such as leaf, shoot and root biomass accumulation, stem height, leaf area, relative growth rate and net assimilation rate. Irrespective of carbon dioxide and PPFD, invariably genotypes differed significantly in macro-micronutrient uptake parameters such as concentration, uptake, influx, transport and use efficiency. With few exceptions, raising PPFD from 100 to 400 μmol·m-2·s-1 and carbon dioxide from 400 to 700 μmol·mol-1 increased nutrient use efficiency for all the cacao genotypes. Elevated carbon dioxide and adequate PPFD are beneficial in improving cacao growth and mineral nutrient uptake and use efficiency.

Fungos micorrízicos arbusculares na tolerância a seca: resposta no metabolismo antioxidante de Ocimum basilicum L.

O manjericão apresenta grande importância devido ao alto teor de substâncias bioativas presentes nas folhas, amplamente utilizada na medicina tradicional e na indústria farmacêutica. No entanto, como na maioria das plantas, mudanças fisiológicas e bioquímicas ocorrem em plantas de manjericão submetidas à seca. A fim de minimizar essas mudanças fungos micorrízicos arbusculares (FMAs) tem sido utilizado. Este estudo teve como objetivo avaliar o crescimento e a resposta antioxidante de plantas de manjericão sob déficit hídrico e inoculados com Clarideoglomus etunicatum. O estudo foi feito em câmera de crescimento em plantas de manjericão inoculadas com FMAs e submetidas à seca após 30 dias após o transplante. Mudas inoculadas com FMA mostraram uma taxa de colonização de 28,66 e 32,79%. Plantas sem a inoculação e submetidas à seca apresentaram redução significativa no diâmetro do caule, comprimento da parte aérea e raiz e no acúmulo de biomassa da parte aérea e sistema radicular. Com a inoculação, houve uma melhora na resposta fisiológica das plantas sob estresse hídrico, referente a concentração de clorofila e o teor relativo de água. Grandes quantidades de prolina se acumularam nas folhas inoculadas e sob estresse, o que mostra o papel benéfico desse osmolitos em manjericão submetido à seca. As enzimas antioxidantes CAT e APX apresentaram maior atividade nas plantas expostas à seca e inoculadas com FMAs, o que reduziu o dano da membrana plasmática. A inoculação com FMAs em manjericão regulou positivamente a síntese de osmolitos e o metabolismo antioxidante promovendo tolerância à seca.

Fruit Yields Depend on Biomass and Nutrient Accumulations in New Shoots of Citrus Trees

New shoots (including newly formed leaves and twigs) and fruits of citrus tree are key organs for present yield formation and flower differentiation in the next season, but the relationship between yield fluctuation and accumulations of major nutrients in new shoots and fruits of citrus tree is still unclear. Thus, to quantify the biomass and mineral nutrient accumulation in new shoots and fruits of citrus trees under varied yield levels has essential significance for rational fertilization and pruning management for citrus orchards. The purpose of this study was, therefore, to investigate the accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), and the distribution of biomass in new shoots and fruits of citrus trees under low, medium and high-yield levels in each of eight orchards located in Chongqing, China. The results showed that substantial variation of fruit yield was observed in all eight orchards with an average yield of 15.0 (low), 30.9 (medium) and 60.1 (high) kg/plant. The averaged biomass of new shoots ranged from 1.59 to 2.51 kg/plant, which was significantly and positively correlated with fruit yield. Nutrient accumulation in leaves was generally highest among new organs, while more than half of N (52.70–71.4%), P (66.5–80.4%) and K (68.9–85.9%) accumulated in fruit. Fruit yields closely correlated with total amounts of major nutrients in new shoots. Furthermore, the nutrient requirements per unit of newly developed shoots and fruits were gradually decreased with increased yield, but the removed nutrients per ton of fresh fruit were almost stable, indicating that more nutrients were distributed into fruit tissues. Taken together, these findings are valuable for optimizing nutrient and pruning management in citrus orchards in China and other similar countries.

Cryptochrome 1a of tomato mediates long-distance signaling of soil water deficit

Although the blue light photoreceptors cryptochromes mediate the expression of genes related to reactive oxygen species, whether cryptochrome 1a (cry1a) regulates local and long-distance signaling of water deficit in tomato (Solanum lycopersicum L.) is unknown. Thus the cry1a tomato mutant and its wild-type (WT) were reciprocally grafted (WT/WT; cry1a/cry1a; WT/cry1a; cry1a/WT; as scion/rootstock) or grown on their own roots (WT and cry1a) under irrigated and water deficit conditions. Plant growth, pigmentation, oxidative stress, water relations, stomatal characteristics and leaf gas exchange were measured. WT and cry1a plants grew similarly under irrigated conditions, whereas cry1a plants had less root biomass and length and higher tissue malondialdehyde concentrations under water deficit. Despite greater oxidative stress, cry1a maintained chlorophyll and carotenoid concentrations in drying soil. Lower stomatal density of cry1a likely increased its leaf relative water content (RWC). In grafted plants, scion genotype largely determined shoot and root biomass accumulation irrespective of water deficit. In chimeric plants grown in drying soil, cry1a rootstocks increased RWC while WT rootstocks maintained photosynthesis of cry1a scions. Manipulating tomato CRY1a may enhance plant drought tolerance by altering leaf pigmentation and gas exchange during soil drying via local and long-distance effects.

Enhancing potassium content in leaves and stems improves drought tolerance of eucalyptus clones.

Eucalyptus are widely planted in regions with low rainfall, occasioning frequent drought stresses. To alleviate the stress-induced effects on plants growing in these environments, soil fertilization with potassium (K) may affect drought-adaptive plant mechanisms, notably on tropical soils with low K availability. This work aimed to evaluate the K dynamic nutrition in eucalyptus in response to soil-K and -water availabilities, correlating the K-nutritional status with the physiological responses of contrasting eucalyptus clones to drought tolerance. A complete randomized design was used to investigate the effects of three water regimes (well-watered, moderate water deficit, and severe water deficit) and two K soil supplies (sufficient and low K) on growth and physiological responses of two elite eucalyptus clones: "VM01" (Eucalyptus urophylla × camaldulensis) and "AEC 0144" (E. urophylla). Results depicted that the K-well-nourished E. urophylla × camaldulensis clone under severe water deficit maintained shoot biomass accumulation by upregulating the K-content in leaves and stems, gas exchange, water-use efficiency (WUEI ), leaf water potential (Ψw), and chlorophyll a fluorescence parameters, compared to E. urophylla clone. Meanwhile, E. urophylla with a severe water deficit showed a decreased of K content in leaves and stem, as well as a reduction in the accumulation of dry mass. Therefore, the K-use efficiency and the apparent electron transport rate through photosystem II were positively correlated in plants grown in low K, indicating the importance of K in maintaining leaf photochemical processes. In conclusion, management strategy should seek to enhance K-nutrition to optimize water-use efficiencies and photosynthesis.

Native rhizobia from southern Brazilian grassland promote the growth of grasses

Soil communities support great biodiversity, as well as their interaction with the plants, can be equally diverse. In this work, we focused our attention on investigating the effect of native rhizobia from Brazilian grassland as a plant growth-promoting rhizobacteria for grasses. We suggest that the positive effect of rhizobacteria on plants is context-dependent, and native species may present better adaptability under certain soil conditions (i.e. acidity, nutrient availability, interaction with other organisms in the rhizosphere). To explore this iteration among native rhizobia and grasses, we isolated rhizobia from Desmodium incanum, a native legume from Brazilian grassland, and inoculated on oats (Avena sativa) and maize (Zea mays). Firstly, we characterized the ability of those rhizobia in solubilizing phosphate and producing indole-acetic acid. Next, under greenhouse conditions, we inoculated grasses with the isolates that presented at least one mechanism of plant growth promotion. After 45 days, we measured the effect of those rhizobia on both morphological and nutritional attributes of grasses. Our finding showed that rhizobia isolated from Desmodium incanum improve the growth of grasses by increasing shoot and root biomass, plant height, and nutrient accumulation in leaves. The most efficient isolate was UFRGS-Dinc1, perhaps due to its ability in solubilize phosphate and produce indole-acetic acid. However, we also noted that UFRGS-Dinc3, that presented the highest phosphate solubilization index, and UFRGS-Dinc18, that produce only indole-acetic acid, could also promote plant growth of grasses. Our results provide pieces of evidence that native rhizobia from Desmodium incanum can promote the growth of grasses, indicating their potential in increasing the yield of crop cultures.

Acquired salinity tolerance in rice: Plant growth dataset.

This article describes the growth of 18 acclimatized and 11 non-acclimatized rice varieties grown in a hydroponic nutrient solution in a glasshouse. Four plants from each variety were grown under control conditions, salinity stress following control conditions (salinity), and salinity stress following acclimation (salinity/acclimation) conditions. Sampling was performed at the end of the salinity treatment (36 days of growth). Growth traits such as shoot and root biomass accumulation and lengths were measured for each variety, and the average was calculated using four replicates. This dataset may aid interested researchers in making comparisons with their data and further advance the research on the salinity acclimation process in rice.

Airborne and belowground phytotoxicity of invasive Ageratina adenophora on native species in Nepal

Volatile compounds from leaf litter of invasive alien Ageratina adenophora are known to inhibit growth of native species in sub-tropical Asia, but there is not much evidence if the litter affects tree species. In particular, the relative importance of airborne inhibition versus belowground effect of invaded soil on tree species is rarely explored. We used A. adenophora uninvaded and invaded soils to follow germination and seedling growth of a native Nepalese tree Schima wallichii (DC.) Korth. in the presence and absence of leaf litter of A. adenophora. We also compared diversity of native species in the uninvaded and invaded sites in Nepal. We found that A. adenophora invasion is associated with lower native species richness and correlated with lower tree canopy cover. Invaded soil and the proximity of A. adenophora leaf litter decreased seed germination rate of S. wallichii. Both invaded soil and leaf litter of the weed inhibited S. wallichii shoot and root biomass accumulation independently of each other. As far as we know, this is the first study to report these two effects simultaneously. In conclusion, belowground effects of A. adenophora invaded soil and airborne effects of leaf litter have a potential to inhibit native tree regeneration in Nepalese Schima–Alnus forests. Maintaining high canopy cover and removing litter of the weed should be tested to control its invasion.

Dissection of quantitative trait loci for root characters and day length sensitivity in SynOpDH wheat (Triticum aestivum L.) bi-parental mapping population

AbstractThe genetics of the root system is still not dissected for wheat and lack of knowledge prohibits the use of marker-assisted selection in breeding. To understand the genetic mechanism of root development, Synthetic W7984 × Opata M85 doubled-haploid (SynOpDH) mapping population was evaluated for root and shoot characteristics in PVC tubes until maturity. Two major quantitative trait loci (QTLs) for total root biomass were detected on homoeologous chromosomes 2A and 2D with logarithm of the odds scores between 6.25–10.9 and 11.8–20.86, and total phenotypic effects between 12.7–17.7 and 26.6–40.04% in 2013 and 2014, respectively. There was a strong correlation between days to anthesis and root and shoot biomass accumulation (0.50–0.81). The QTL for biomass traits on chromosome 2D co-locates with QTL for days to anthesis. The effect of extended vegetative growth, caused by photoperiod sensitivity (Ppd) genes, on biomass accumulation was always hypothesized, this is the first study to genetically support this theory.

Contrasting Responses to Stress Displayed by Tobacco Overexpressing an Algal Plastid Terminal Oxidase in the Chloroplast.

The plastid terminal oxidase (PTOX) – an interfacial diiron carboxylate protein found in the thylakoid membranes of chloroplasts – oxidizes plastoquinol and reduces molecular oxygen to water. It is believed to play a physiologically important role in the response of some plant species to light and salt (NaCl) stress by diverting excess electrons to oxygen thereby protecting photosystem II (PSII) from photodamage. PTOX is therefore a candidate for engineering stress tolerance in crop plants. Previously, we used chloroplast transformation technology to over express PTOX1 from the green alga Chlamydomonas reinhardtii in tobacco (generating line Nt-PTOX-OE). Contrary to expectation, growth of Nt-PTOX-OE plants was more sensitive to light stress. Here we have examined in detail the effects of PTOX1 on photosynthesis in Nt-PTOX-OE tobacco plants grown at two different light intensities. Under ‘low light’ (50 μmol photons m–2 s–1) conditions, Nt-PTOX-OE and WT plants showed similar photosynthetic activities. In contrast, under ‘high light’ (125 μmol photons m–2 s–1) conditions, Nt-PTOX-OE showed less PSII activity than WT while photosystem I (PSI) activity was unaffected. Nt-PTOX-OE grown under high light also failed to increase the chlorophyll a/b ratio and the maximum rate of CO2 assimilation compared to low-light grown plants, suggesting a defect in acclimation. In contrast, Nt-PTOX-OE plants showed much better germination, root length, and shoot biomass accumulation than WT when exposed to high levels of NaCl and showed better recovery and less chlorophyll bleaching after NaCl stress when grown hydroponically. Overall, our results strengthen the link between PTOX and the resistance of plants to salt stress.

Nutrient retranslocation in Larix principis-rupprechtii Mayr relative to fertilization and irrigation

Nutrient retranslocation from senescing foliage to perennial organs is critical for nutrient conservation and a mechanism of plant adaptation to low-fertility soils. And it has been well documented for evergreen species and for deciduous broadleaf tree species. Meanwhile, subirrigation (SI) and fertilization are used to improve the production efficiency of seedlings, however, little is known about how retranslocation in deciduous conifer seedlings is affected by SI or soil fertility. We fertilized Larix principis-rupprechtii Mayr seedlings with 50, 100, and 150 mg N per seedling using SI and overhead irrigation (OI). Seedling growth and nutrient status, at both pre-senescence (T1) and post-abscission (T2) moments, and growing media electrical conductivity were measured to (1) explore relationships between foliar nutrient retranslocation and (a) growth, (b) nutrient status, and (c) media fertility, and (2) examined how these are affected by irrigation method and fertilizer rate. Fertilizer rate and irrigation method had little effect on seedling growth, with the exception of root mass, but N, P, and K concentrations increased with increasing soil fertility and both concentrations and contents were greater under SI compared to OI. Foliar N and K retranslocation was lower under SI compared to OI across all fertilizer rates, while foliar P retranslocation was lower only at the highest fertilizer rate for SI-seedlings. For OI-seedlings, retranslocation was unaffected by fertilizer rate, with average N, P, and K retranslocation efficiencies of 71%, 29%, and 55%, respectively. However, retranslocation in SI-seedlings declined as fertilizer rates increased. Foliar nutrient retranslocation directly correlated with seedling biomass accumulation over the growing season (up to T1) and inversely correlated with soil fertility, shoot biomass accumulation during hardening (from T1 to T2), and T1 nutrient concentration in roots (N, P, and K) and stems (N and K). Understanding nutrient retranslocation dynamics for deciduous woody plants informs more effective nutrient management regimes for seedling production under SI.