Assimilate Partitioning Research Articles

Sulphur on Groundnut Yield and Quality

Groundnut yield is enhanced by the sulfur supplement which aids in the improvement of chlorophyll synthesis leading to higher partitioning of assimilates resulting in high growth and yield parameters. Sulfur deficiency results in poor flowering, fruiting, cupping of leaves, reddening of stems, petiole and stunted growth. Sulfur is required for the synthesis of protein, oils and vitamins. Methionine (21 % S), cysteine (26 % S), Cystine (27 % S) are important amino-acids that are supplied by sulfur triggers protein synthesis and biochemical reactions that increases oil content and oil quality .Variety of sulfur sources and levels had been tried in experiments by researchers to evaluate the potential level that sustains high growth, yield and productivity of groundnut resulting in higher net returns. Application of sulfur about 40-60 kg ha-1 proved to an optimistic level through gypsum sources for groundnut.

Different root strategies of perennial native grasses under two contrasting water availability conditions: implications for their spatial distribution in desert dunes

The distribution pattern of perennial native grasses in the dune systems of the Monte desert might be determined by the ability of plant roots to acquire water under drought conditions in different topographical positions and soil substrates. This study examined differences in root traits of two species growing in sand dunes, Aristida mendocina and Panicum urvilleanum, and two species growing in interdune valleys, Pappophorum caespitosum and Leptochloa crinita, under different water availability conditions in a sand substrate. Grasses were grown in rhizotrons and the factorial design included species, irrigation treatments, days from sowing, and depth soil profile. Root length, total root length, number of root branches, length of root branches-to-number of root branches ratio (LB:NB), daily elongation rate (DER), root length density (RLD), root angles, aerial and root dry mass, and shoot-to-root ratio (S:R) were measured. The four species studied were affected by drought conditions causing a decrease in root growth and modifying root structure, partition of assimilates, root angles, and exploration of the soil profile. However, we found that species from sand dunes were less affected by drought and showed a deeper root exploration under drought conditions, mainly due to proliferation of longer and more lateral roots in the deepest soil layer. The different root traits and responses of the species under drought conditions would imply adaptations to the topographical position each species occupies and could explain their spatial distribution in desert dunes.

Terminal drought and heat stress alter physiological and biochemical attributes in flag leaf of bread wheat.

Heat stress along with low water availability at reproductive stage (terminal growth phase of wheat crop) is major contributing factor towards less wheat production in tropics and sub-tropics. Flag leaf plays a pivotal role in assimilate partitioning and stress tolerance of wheat during terminal growth phase. However, limited is known about biochemical response of flag leaf to combined and individual heat and drought stress during terminal growth phase. Therefore, current study investigated combined and individual effect of terminal drought and heat stress on water relations, photosynthetic pigments, osmolytes accumulation and antioxidants defense mechanism in flag leaf of bread wheat. Experimental treatments comprised of control, terminal drought stress alone (50% field capacity during reproductive phase), terminal heat stress alone (wheat grown inside plastic tunnel during reproductive phase) and terminal drought stress + terminal heat stress. Individual and combined imposition of drought and heat stresses significantly (p≤0.05) altered water relations, osmolyte contents, soluble proteins and sugars along with activated antioxidant defensive system in terms of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX). Turgor potential, POD and APX activities were lowest under individual heat stress; however, these were improved when drought stress was combined with heat stress. It is concluded that combined effect of drought and heat stress was more detrimental than individual stresses. The interactive effect of both stresses was hypo-additive in nature, but for some traits (like turgor potential and APX) effect of one stress neutralized the other. To best of our knowledge, this is the first report on physiological and biochemical response of flag leaf of wheat to combine heat and drought stress. These results will help future studies dealing with improved stress tolerance in wheat. However, detailed studies are needed to fully understand the genetic mechanisms behind these physiological and biochemical changes in flag leaf in response to combined heat and drought stress.

Estimation of tomato yield gaps for greenhouse in Uruguay

Yield gap analysis is a powerful method to explore gap’s breadth between potential yields, attainable and those realized in farmers’ fields, identifying constraints to production and assess opportunities to yield increase. We assessed yields and yield components across two seasons, in 110 greenhouse tomato (Solanum lycopersicum) crops during 2014/15 and 2015/16 in the south region of Uruguay, and compared them with potential and attainable yield. Potential yield was calculated with a simulation model based on photosynthetic active radiation (PAR) and light use efficiency, and TOMSIM to estimate assimilate partition and fruit yield. Since yield was primarily determined by cumulative PAR intercepted, a boundary function was fitted to estimate attainable yield as a function of cumulative PAR intercepted. Our study quantified a yield gap of 10.7 kg m−2 or 44 % relative to potential. Overall gap was divided into three components: difference between actual and attainable (45 % of total gap), attainable and potential with actual greenhouse PAR transmissivity (29 % of total gap) and between potential with actual transmissivity and potential with 70 % of greenhouse transmissivity (26 % of total gap). For long summer and short spring/summer crops the greatest impact in yield could be obtained by increasing leaf area index by reducing plant lowering operations and leaf pruning intensity, and by increasing plant density. For autumn crops, yield could be improved by earlier planting, reducing leaf pruning intensity after harvest beginning, and increasing greenhouse transmissivity by more frequent plastic cover renewal and removing roofs’ shading screens and whitening.

Alternative polyadenylation of the stacyose synthase gene mediates source-sink regulation in cucumber

Alternative polyadenylation (APA) is a pervasive mechanism for gene regulation in eukaryotes. Stachyose is the main assimilate translocated in the cucumber phloem. Stachyose synthase (CsSTS) catalyzes the last step of stachyose biosynthesis in cucumber leaves and plays a key role in the regulation of assimilate partitioning between source and sink. In this study, three CsSTS mRNAs with the same open reading frame and the 5`untranslated region (UTR), but differing in their 3`UTRs, named CsSTS1 (short), CsSTS2 (medium), and CsSTS3 (long), were identified. Southern blot and sequence analysis of the cucumber genome confirmed that these transcripts are regulated through APA from a single gene. No significant difference of in vitro translation efficiency was found among three mRNAs. However, the relative stabilities of three transcripts varied among different tissues and different leaf development stages of cucumber. CsSTS1 expression in cucumber calli was up-regulated by the raffinose (substrate of CsSTS) and down-regulated by stachyose (product of CsSTS), respectively. In cucumber plants, all three isoforms have considerable expression in non-fruit node leaves. However, in fruit-carrying node leaves, the expression of CsSTS2 and CsSTS3 was severely inhibited and only CsSTS1 was highly expressed, indicating fruit setting has a remarkable effect on the relative expression level of three transcripts. This “fruit setting” effect could be observed until at least 36 h after the fruit was removed from the node. Our results suggest that abundant expression of CsSTS1 is beneficial for stachyose loading in source leaves, and APA is a delicate mechanism for CsSTS to regulate cucumber source-sink balance.

Response of photosynthate distribution in potato plants to different LED spectra.

Although light is essential to photosynthesis, few studies have examined the effects of different LED spectra on photosynthate distribution in potato plants. Therefore, we exposed tuberising potato plants to white (W), red (R), blue (B) and green (G) LED treatments and compared tuber development and carbohydrate partitioning among the plants. R-treated plants had greater photosynthetic leaf area during tuber development compared with those under other treatments, thus enhancing assimilation. Although R-treated plants had higher 13C assimilation in the leaves, stems and roots than those under B treatment, there was no difference in partitioning of 13C assimilation and yield in the tubers of each plant between R and B treatments. For the tuber size, R-treated plants had a higher ratio of large tubers (>20 g) and a lower ratio of small (2-20 g) and medium-sized (10-20 g) tubers than those under W. B-treated plants had more medium-sized and large tubers than those under W. The reason may be that plants under R treatment distributed more assimilated 13C in their first tuber than those under other treatments. By contrast, plants under B balanced photosynthate distribution among their tubers. Leaves under G treatment had lower photosynthetic efficiency and ΦPSII than those under W, R or B treatment, which resulted in lower 13C photosynthate allocation in organs and lower tuber yield per plant than in R and B treatments. Overall, R treatment promoted 13C assimilation and led to more large tubers than other treatments. B-treated plants distributed more photosynthates into tubers rather than other organs and showed balanced tuber development.

Determination of assimilate partitioning at different growth stages of potato plant under water stress conditions

Determination of assimilate partitioning at different growth stages of potato plant under water stress conditions

Relación fuente-destino en cultivares de maní tipo runner (Arachis hypogaea L.) sembrados en Argentina

La partición de asimilados a frutos es una característica fisiológica de relevancia para el aumento del rendimiento de maní y su análisis mediante la relación fuente-destino aporta al mejoramiento genético y manejo del cultivo. El objetivo fue analizar la relación fuente-destino en cultivares runner sembrados en Argentina. Se realizaron dos experimentos a campo, en el Exp1 el cultivar Granoleico fue sembrado en tres fechas durante 2009-2010 y 2010-2011. En el Exp2 fueron sembrados seis cultivares runner (Florunner, Florman, Manigran, Asem-485, Pepe-Asem y Granoleico) durante 2011-2012. La relación fuente-destino se analizó con dos metodologías: la biomasa total asignada a cada fruto durante su llenado con relación a su peso final, y el análisis de la relación entre peso y número de frutos a cosecha. La falta de compensación entre número y peso de frutos demostró que el maní podría llenar un amplio número de frutos (entre 20 y 57 frutos planta-1). Además, el peso medio de un fruto (1,05 g) fue menor al crecimiento total de la planta asignado a él durante su período de formación (2,63 g). Se determinó una limitación por destinos, indicando la posibilidad de aumentar el rendimiento a través del incremento del tamaño de los destinos.

Understanding the Genetic Basis of Spike Fertility to Improve Grain Number, Harvest Index, and Grain Yield in Wheat Under High Temperature Stress Environments.

Moderate heat stress accompanied by short episodes of extreme heat during the post-anthesis stage is common in most US wheat growing areas and causes substantial yield losses. Sink strength (grain number) is a key yield limiting factor in modern wheat varieties. Increasing spike fertility (SF) and improving the partitioning of assimilates can optimize sink strength which is essential to improve wheat yield potential under a hot and humid environment. A genome-wide association study (GWAS) allows identification of novel quantitative trait loci (QTLs) associated with SF and other partitioning traits that can assist in marker assisted breeding. In this study, GWAS was performed on a soft wheat association mapping panel (SWAMP) comprised of 236 elite lines using 27,466 single nucleotide polymorphisms (SNPs). The panel was phenotyped in two heat stress locations over 3 years. GWAS identified 109 significant marker-trait associations (MTAs) (p ≤ 9.99 x 10−5) related to eight phenotypic traits including SF (a major component of grain number) and spike harvest index (SHI, a major component of grain weight). MTAs detected on chromosomes 1B, 3A, 3B, and 5A were associated with multiple traits and are potentially important targets for selection. More than half of the significant MTAs (60 out of 109) were found in genes encoding different types of proteins related to metabolism, disease, and abiotic stress including heat stress. These MTAs could be potential targets for further validation study and may be used in marker-assisted breeding for improving wheat grain yield under post-anthesis heat stress conditions. This is the first study to identify novel QTLs associated with SF and SHI which represent the major components of grain number and grain weight, respectively, in wheat.

There are Different Pathways to Stable Spring Wheat Grain Yield and Nitrogen Utilization Efficiency in Conventional and Organically‐Managed Systems

The high costs and negative environmental impact associated with the use of N in crop production suggest we need to improve our knowledge of crop N utilization efficiency (NUtE: the amount of grain produced per unit of N uptake). We conducted a study in organic and conventional fields to compare the effect of management and genetic variability for grain yield and NUtE in spring wheat (Triticum aestivum L.). We also assessed the relationships between yield and NUtE stability among tested cultivars under organic management. Grain yield and NUtE were 50 and 20% less in organic compared to conventional management (1.62 and 3.27 t ha−1 for grain yield and 16.2 and 20.9 t DM t−1 N for NUtE, respectively). Analyses of variance revealed significant effects of genotype (G), environment (E) (year × location), and G × E interactions on grain and NUtE in organic environments. Traits in the organic system that were sensitive to G × E interactions included grain yield, harvest index (HI), NUtE, and dry matter production. Four modern cultivars with differing genotypic characteristics (medium tall stature, disease and pest resistant, and semi‐dwarf), had high and stable grain yield, and NUtE in both systems. Our results suggest that the modern wheat cultivars CDC Kernen, CDC Stanley, Carberry, and Unity may be suitable for organic systems because of their stable yield and NUtE across tested environments. Such characteristics could be advantageous under organic farming systems where temporal and spatial variations of resources are normally greater than conventional systems.Core Ideas Nitrogen utilization efficiency has gentotype × environment interactions in organic fields. Low harvest index in organic systems indicates reduced assimilate partitioning due to weed competition. Four modern cultivars with different traits exhibited consistent grain yield in organic systems. Different traits in the four cultivars may be key for organic crop production.

An experimentally-calibrated model of photosynthesis, assimilate partitioning and tuber yield in cassava in response to water supply to assist crop management and improvement

A model (DYNCAS 1.0) is presented of photosynthesis and partitioning of carbon-based (C) assimilate to respiration and growth of leaves, stems, tubers and roots in cassava in response to environmental atmospheric conditions and water supply. It comprises 9 state variables and 40 parameters (including 7 functional relationships), all of direct physiological significance. The important characteristic of the model is the simultaneous consideration of assimilate supply and crop water status by hourly calculations that integrate diurnal physiological responses of photosynthesis, respiration and transpiration to seasonal crop growth and water use under existing environmental conditions.Crop photosynthesis is the integral of a single leaf-response through the canopy according to intercepted radiation determined by an extinction coefficient and by temperature together with canopy conductance determined from crop water potential and vapour pressure deficit. Respiration of organs is calculated individually according to chemical composition and growth processes, including mobilization of reserves. Transpiration proceeds with photosynthesis according to canopy conductance, but in response to evaporative demand, extracting water from the root zone depending upon crop and soil water potentials and the root length that explores it. Partitioning of carbon assimilate from a single crop pool to leaves, stems, tubers and roots depends upon diurnal oscillations in supply according to organ-specific Michaelis-Menten kinetics. Phenological development, here the branching of stems, rate of node and leaf production, and maturity and senescence of leaves and of roots, is determined by temperature and crop water status.The model is shown to capture the response reported in a published study of the growth and yield of two cultivars of cassava of distinct branching habit to water supply. The principles of assimilate partition and the simulation of diurnal responses of growth processes employed here are presented as a guide for further research in cassava productivity and response to environment and management.

Utilización de efluentes urbanos tratados para la producción de brócoli mediante riego por goteo subterráneo

<p class="western" style="margin-bottom: 0cm; line-height: 150%;" lang="es-ES" align="justify"><a name="_Hlk6045826"></a> La utilización de efluentes constituye una alternativa viable en la producción agrícola, transformando un desperdicio en un recurso útil, aportando agua y nutrientes a los cultivos. <span style="color: #212121;">El </span>objetivo del estudio fue evaluar la utilización de efluentes urbanos tratados en la producción de brócoli (<em>Brassica oleracea</em> var. itálica). Los tratamientos resultaron de la combinación de tres cultivares: ‘Matsuri’ (C1), ‘Green Pia’ (C2) y ‘Almanor’ (C3), y dos fuentes de riego: efluentes urbanos tratados (EUT) y agua de acuífero (AC), suministrado mediante riego por goteo subterráneo durante dos temporadas (E1 y E2). El diseño experimental fue en parcelas divididas. A la cosecha se evaluó partición de asimilados en hojas, tallo y pella, <span style="color: #000000;">diámetro de pella, </span>rendimiento fresco y <span lang="es-AR">calidad sanitaria del producto mediante análisis microbiológicos y parasitológicos. L</span>os resultados determinaron diferencias significativas (<em>p</em>? 0,05 Fisher) en rendimiento para los cultivares C2 y C3 (E1) regados con EUT. El diámetro de pellas presentó diferencias para C2, C3 (E1) y C3 (E2). En E1 las condiciones ambientales fueron más favorables, influyendo en el rendimiento de los cultivares. La calidad sanitaria de las pellas determinó que fueron aptas para su consumo en fresco, lo que demuestra <span lang="es-AR">que </span>esta tecnología podría ser utilizada en la producción de brócoli.</p>

The Soybean Sugar Transporter GmSWEET15 Mediates Sucrose Export from Endosperm to Early Embryo.

Soybean (Glycine max) seed is primarily composed of a mature embryo that provides a major source of protein and oil for humans and other animals. Early in development, the tiny embryos grow rapidly and acquire large quantities of sugars from the liquid endosperm of developing seeds. An insufficient supply of nutrients from the endosperm to the embryo results in severe seed abortion and yield reduction. Hence, an understanding of the molecular basis and regulation of assimilate partitioning involved in early embryo development is important for improving soybean seed yield and quality. Here, we used expression profiling analysis to show that two paralogous sugar transporter genes from the SWEET (Sugars Will Eventually be Exported Transporter) family, GmSWEET15a and GmSWEET15b, were highly expressed in developing soybean seeds. In situ hybridization and quantitative real-time PCR showed that both genes were mainly expressed in the endosperm at the cotyledon stage. GmSWEET15b showed both efflux and influx activities for sucrose in Xenopus oocytes. In Arabidopsis (Arabidopsis thaliana), knockout of three AtSWEET alleles is required to see a defective, but not lethal, embryo phenotype, whereas knockout of both GmSWEET15 genes in soybean caused retarded embryo development and endosperm persistence, resulting in severe seed abortion. In addition, the embryo sugar content of the soybean knockout mutants was greatly reduced. These results demonstrate that the plasma membrane sugar transporter, GmSWEET15, is essential for embryo development in soybean by mediating Suc export from the endosperm to the embryo early in seed development.

Inheritance and Genetic Mapping of the Reduced Height (Rht18) Gene in Wheat.

Short-statured plants revolutionized agriculture during the 1960s due to their ability to resist lodging, increased their response to fertilizers, and improved partitioning of assimilates which led to yield gains. Of more than 21 reduced-height (Rht) genes reported in wheat, only three—Rht-B1b, Rht-D1b, and Rht8—were extensively used in wheat breeding programs. The remaining reduced height mutants have not been utilized in breeding programs due to the lack of characterization. In the present study, we determined the inheritance of Rht18 and developed a genetic linkage map of the region containing Rht18. The height distribution of the F2 population was skewed towards the mutant parent, indicating that the dwarf allele (Rht18) is semi-dominant over the tall allele (rht18). Rht18 was mapped on chromosome 6A between markers barc146 and cfd190 with a genetic distance of 26.2 and 17.3 cM, respectively. In addition to plant height, agronomically important traits, like awns and tiller numbers, were also studied in the bi-parental population. Although the average tiller number was very similar in both parents, the F2 population displayed a normal distribution for tiller number with the majority of plants having phenotype similar to the parents. Transgressive segregation was observed for plant height and tiller number in F2 population. This study enabled us to select a semi-dwarf line with superior agronomic characteristics that could be utilized in a breeding program. The identification of SSRs associated with Rht18 may improve breeders’ effectiveness in selecting desired semi-dwarf lines for developing new wheat cultivars.

EFEITO DA DESFOLHA ARTIFICIAL NO CRESCIMENTO DO VIMEIRO

O vimeiro (Salix x rubens) é uma planta lenhosa, de origem europeia, usada no Brasil para artesanato e movelaria. A cultura do vimeiro é eventualmente atacada por lagartas e formigas que causam a perda de área foliar. Este estudo objetivou avaliar o efeito de níveis de desfolha no crescimento do vimeiro. O experimento foi conduzido em uma estufa. As plantas foram mantidas em vasos com capacidade de 8 litros sob nebulização intermitente, de agosto a dezembro de 2004. O delineamento foi em blocos casualizados, com cinco repetições e quatro tratamentos (0, 25, 50 e 75% de desfolha do número total de folhas) avaliados quanto ao teor de açúcares redutores, área foliar e massa fresca e seca, caules e folhas. O desfolhamento (%) reduziu a massa (MH = -0,1067x + 19,03, R² = 0,98) e o diâmetro final das hastes (DH = -0,0114x + 5,172, R² = 0,98), assim como a massa foliar (MF = -0,1028x + 13,892; R2 = 0,99) e o número de folhas (NF = -0,2545x + 36,87, R² ~ 0,998). A partição de assimilados foi alterada em favor da restauração da área foliar.

Exogenous arginine improved fenugreek sprouts growth and trigonelline production under salinity condition

Fenugreek (Trigonella foenum-graecum L.) is an aromatic and spice herb whose seeds have medicinal and nutraceutical properties. Trigonelline is one of the valuable alkaloids in fenugreek seeds with therapeutic potential for diabetes and central nervous system disease. In order to improve fenugreek sprout growth and trigonelline production, an experiment examining two factors was conducted on the basis of complete randomized design (CRD) with three replications. Fifty healthy seeds were put in petri dish and subjected to different arginine (0, 10, 20, 30 and 40 μM) and/or NaCl concentrations (0, 75 and 150 mM). To identify the best time in which the highest trigonelline content was accumulated and its possible mechanisms, trigonelline, proline and nicotinic acid contents were measured at 4, 8 and 12 days after beginning the experiment. Results showed that the arginine application mitigated the salinity induced reduction in germination and sprout growth. At early stages of sprout growth (4 days after treatments), salinity induced changes in the assimilate partitioning into proline, trigonelline and nicotinic acid accumulation. However, application of arginine adjusted the salinity effects. Over time (4–8 and 12 days after treatments), arginine application together with salinity increased the trigonelline and nicotinic acid content and the highest efficiency was achieved by 20 μM arginine and 150 mM salinity. In general, the highest yield of trigonelline in fenugreek sprouts, as the most important index, was observed when they were subjected to 75 mM NaCl and 20 μM arginine and it was noticeable in 12-day-old ones. Therefore, arginine and NaCl exogenous application, depends on their concentrations, were a valuable method for improving the trigonelline content of fenugreek sprouts.

Use of the beta growth function to quantitatively characterize the effects of plant density and a growth regulator on growth and biomass partitioning in cotton

Allocation of newly formed biomass towards plant organs is a key determinant of plant performance that is affected by agronomic practices such as plant population density and use of growth regulators. Here we quantified biomass allocation of intercropped cotton (Gossypium hirsutum) growing at two population densities (3.0 and 7.5 plants m−2) and with or without application of the growth regulator mepiquat chloride (MC) in three consecutive years. The beta growth function was used to quantitatively characterize the dynamics of biomass partitioning. Compared to low density, high density increased daily growth rate and final above-ground dry matter, but decreased allocation to fruits. Application of MC did not affect dry matter accumulation but increased allocation to fruits by 22%. The parameters of the beta growth function have a clear biological interpretation, providing a useful quantitative characterization of the effect of management on dry matter allocation in cotton. The function may also be used to model organ-specific daily assimilate partitioning as a component in models of plant growth and crop production with the consideration of discussed caveats.

Diurnal periodicity of assimilate transport shapes resource allocation and whole-plant carbon balance.

Whole-plant carbon balance comprises diurnal fluctuations of photosynthetic carbon gain and respiratory losses, as well as partitioning of assimilates between phototrophic and heterotrophic organs. Because it is difficult to access, the root system is frequently neglected in growth models, or its metabolism is rated based on generalizations from other organs. Here, whole-plant cuvettes were used for investigating total-plant carbon exchange with the environment over full diurnal cycles. Dynamics of primary metabolism and diurnally resolved phloem exudation profiles, as proxy of assimilate transport, were combined to obtain a full picture of resource allocation. This uncovered a strong impact of periodicity of inter-organ transport on the efficiency of carbon gain. While a sinusoidal fluctuation of the transport rate, with minor diel deflections, minimized respiratory losses in Arabidopsis wild-type plants, triangular or rectangular patterns of transport, found in mutants defective in either starch or sucrose metabolism, increased root respiration at the end or beginning of the day, respectively. Power spectral density and cross-correlation analysis revealed that only the rate of starch synthesis was strictly correlated to the rate of net photosynthesis in wild-type, while in a sucrose-phosphate synthase mutant (spsa1), this applied also to carboxylate synthesis, serving as an alternative carbon pool. In the starchless mutant of plastidial phospho-gluco mutase (pgm), none of these rates, but concentrations of sucrose and glucose in the root, followed the pattern of photosynthesis, indicating direct transduction of shoot sugar levels to the root. The results demonstrate that starch metabolism alone is insufficient to buffer diurnal fluctuations of carbon exchange.

A knowledge-and-data-driven modeling approach for simulating plant growth and the dynamics of CO2/O2 concentrations in a closed system of plants and humans by integrating mechanistic and empirical models

Modeling and the prediction of material flows (plant production, CO2/O2 concentrations, H2O) is an important but challenging task in the design and control of closed ecological life support systems (CELSS). The aim of this study was to develop a novel knowledge-and-data-driven modeling (KDDM) approach for simultaneously simulating plant production and CO2/O2 concentrations in a closed system of plants and humans by integrating mechanistic and empirical models.The KDDM approach consists of a ‘knowledge-driven (KD)’ sub-model and a ‘data-driven (DD)’ sub-model. The KD sub-model describes hourly and up to daily plant photosynthesis, respiration and assimilation partitioning using the components of GreenLab and TomSim models. The DD sub-model describes the dynamics of CO2 production and O2 consumption by the crew member using a piecewise linear model. The two sub-models were integrated with a mass balance model for CO2/O2 concentrations in a closed system.The KDDM was applied with a two-person, 30-day integrated CELSS test. This model provides accurate computation of both the dry weights of different plant compartments and CO2/O2 concentrations. The model also quantifies the underlying material flows among the crew members, plants and environment.This approach provides a computational basis for lifetime optimization of cabin design and experimental setup of CELSS (e.g., environmental control, planting schedule). With extension, this methodology can be applied to a half-closed system such as a glasshouse.

Phloem transport capacity of transgenic rice T1c-19 (Cry1C*) under several potassium fertilizer levels.

Genetic modification of Cry-proteins from Bacillus thuringiensis (Bt) is a common practice in economically important crops to improve insecticide resistance and reduce the use of pesticides. However, introduction of these genes can have unintended side effects, which should be closely monitored for effective breeding and crop management. To determine the potential cause of these negative effects, we explored assimilate partitioning in the transgenic Bt rice line T1c-19 (Cry1C*), which was compared with that of its wild-type counterpart Minghui 63 (MH63) under different potassium fertilization application treatment conditions. In a pot experiment, 0, 0.4, and 0.6 g K2O was applied per kg of dry soil to determine the phloem transport characteristics of the two rice lines. We used a variety of assessment indicators ranging from morphological to physiological aspects, including the number of large and small vascular bundles in the neck internode at the heading stage, the diameter and bleeding intensity of the neck internode at the filling stage, and the content and apparent ratio of transferred non-structural carbohydrates (NSC) in the culm and sheath from the heading to maturing stages. The K utilization and grain yield at the maturing stage were also concerned. Results presented that the mean setting rate and grain yield of T1c-19 (Cry1C*) decreased by 22.3% and 26.2% compared to those in MH63, respectively. Compared to MH63, the K concentration and accumulation were significantly higher in the culms and leaves, but significantly lower in grain of T1c-19 (Cry1C*). T1c-19 (Cry1C*) had less apparent NSC efflux in the culm and sheath, fewer small vascular bundles, and a smaller diameter and bleeding intensity of the neck internode than MH63. In addition, linear correlation analysis indicated that there were positive correlations among grain yield, setting rate, the apparent NSC efflux in the culm and sheath, number of small vascular bundles, and the neck internode diameter and bleeding intensity. These unintended effects may directly or indirectly be caused by insertion of exogenous Bt (Cry1C*) gene, which should be further considered in the future breeding of transgenic crops.