Unit Leaf Surface Research Articles

Influence of Fertilizer Systems and Tillage Methods on the Formation of the Assimilation Apparatus and Photosynthesis Productivity of Winter Wheat and Sugar Beet in the Central Chernozem Region

The effect of fertilizers and soil tillage on the photosynthesis productivity of winter wheat and sugar beet crops was studied in a stationary field experiment on leached chernozem of the Central Chernozem region. It was found that a significant increase in crop yield is achieved by optimizing soil tillage and fertilization, as well as by increasing the total area of the leaf surface, the photosynthetic productivity of which decreased per unit of leaf surface.

FUNCTIONAL RELATIONSHIPS BETWEEN THE HEMIPARASITIC PLANT RHINANTHUS RUMELICUS Velen AND ITS HOST SPECIES

Rhinanthus rumelicus Velen is a hemiparasitic herbaceous species commonly found in hill and lowland meadows, particularly in areas where arable land has been abandoned and converted into grassland. As a result, it can be inferred that this species has an impact on community structure, vegetation zonation, and the dynamics of plant populations.Physiologically, the species extracts a portion of the raw sap from its host plants. The photosynthesis process occurs with intensities similar to those of autotrophic plants. Research has indicated that Rhinanthus rumelicus plants exhibit a more intense respiration process compared to their host plants. While the intensity of their photosynthesis is within the normal range for a unit of leaf surface, the quantity of organic substances generated by this process is minimal, as these substances are primarily consumed during the respiratory process.

Photosynthetic activity of winter wheat depending on fertilization and lime application on sod-podzolic soil in the conditions of Western Polissia

Topicality. Increasing the productivity of crop photosynthesis, i.e. the amount of organic matter synthesised per unit of leaf surface in a day, is an essential condition for high crop yields. The area of the leaf surface depends on the biometric parameters of the plant, the nutritional regime, as well as the duration of leaf activity, which significantly affects the accumulation of organic matter. Purpose. To identify the influence of mineral nutrition optimization and chemical amelioration on the formation of leaf surface area, photosynthetic potential, and net photosynthetic productivity in the main development stages of winter wheat grown on sod-podzolic soil in the conditions of the Western Polissia. Methods. Field experiment, calculation and statistical methods. Results. In particular, with the application of dolomite powder at a dose of 1.0 Hh and different fertilisation variants, the leaf surface area of plants increased from 1.5 ths. m2/ha to 4.12– 6.99 ths. m2/ha in the tillering stage, from 4.07 ths. m2/ha to 14.16–21.34 ths. m2/ha in the stem elongation stage, and from 2.59 ths. m2/ha to 5.33–9.49 ths. m2/ha in the heading stage, respectively, compared to the control (without fertilisation). It is noted over the years of research that the application of mineral fertilisers on the background of liming increased the indicator of photosynthetic potential by 2.6–3.5 times compared to non-fertilised one, and the net productivity of photosynthesis increased by 15.4–21.3 % compared to the control. Conclusions. The largest indicators of leaf surface area, photosynthetic potential, and net photosynthetic productivity in the tillering, stem elongation and heading stages were formed by application of N150Р50К125 + S40 + microfertilizer (two applications). The highest photosynthetic activity of winter wheat plants were noted in the stem elongation stage. Key words: winter wheat, fertilization, amelioration, leaf surface area, photosynthetic potential, net photosynthetic productivity

Selection of winter soft wheat for resistance to brown rust

The article presents the results of the phytopathological test and marker analysis of the selection material of winter wheat for resistance to the pathogen of brown rust (Puccinia recondita Rob. ex Desm f. sp. tritici.). The object of research was 10 cultivars of various ecological and geographical origin. Using molecular markers, the studied wheat varieties did not reveal the highly and partially effective genes Lr9, Lr19/Sr25, Lr24/Sr24, Lr41 and Lr47 in Russia, and the ineffective gene Lr20/Sr1. The combination of the Lr34 gene with ineffective genes can provide an increase in the level of field resistance of wheat varieties. In the variety type Leaf 25, the age-related resistance gene Lr37 is assumed to be partially effective in Russia. This type of stability is characterized by a longer latent period, a decrease in the number of pustules per unit leaf surface, their size and the number of spores in the pustule. According to the results of a comprehensive assessment of winter wheat cultivars to brown rust, the following cultivars showed a stable reaction type (R): Zhiva (Lr1, Lr3, Lr10, Lr26, Lr34) and Leaf 25 (Lr1, Lr3, Lr37;); a susceptible reaction type (S) in Malvina cultivars -(Lr1, Lr26;), Solara (Lr1, Lr34), Etude - Lr3. Genes in various combinations can provide field resistance of winter wheat to brown rust. Most cultivars were moderately susceptible to the disease.

Response of Common Ice Plant (Mesembryanthemum crystallinum L.) to Sodium Chloride Concentration in Hydroponic Nutrient Solution

Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible succulent plant with savory flavor. It has epidermal bladder cells (EBCs) that store water and sodium chloride (NaCl) located on the epidermis of the leaves and stems. Ice plant is an obligatory halophyte that requires NaCl for optimum growth. The objective of this study was to determine the impact of NaCl on growth of ice plant for hydroponic production as an edible leafy green and to quantify the ability of ice plant to take up NaCl from the environment. Four-week-old seedlings of ice plant were transplanted into hydroponic systems, established for 1 week, and given five NaCl treatments [0 M (control), 0.05 M, 0.10 M, 0.20 M, 0.40 M NaCl]. Sequential destructive harvests to determine plant growth occurred at day 7, 14, and 21 after NaCl treatment. The 0.05 M NaCl had the greatest stimulating effect on biomass, increasing total fresh weight (FW) by 173% and shoot FW by 193% compared with the control plants. The 0.10 M NaCl also had stimulating effect as compared with 0 M, but plants were not as large as those receiving 0.05 M NaCl. The 0.20 M NaCl had little effect on plant growth compared with the control. The 0.40 M NaCl had a strong stunting effect on plant growth. All plants treated with NaCl had less root weight than the control, and higher NaCl concentration resulted in greater reduction in root weight. However, for the 0.05 and 0.10 M treatment, the gain in shoot weight exceeded the loss in root weight. Plants gained or lost water in a faster rate than dry mass, which resulted in larger differences among treatments in FW than in dry weight (DW). Plants treated with higher NaCl concentrations developed fewer, smaller, and thicker leaves but contained more EBCs per unit leaf surface area. There was high Na and Cl accumulation in leaf tissues of all salt-treated plants (e.g., 180,507 mg·kg−1 Na and 125,084 mg·kg−1 Cl in the 0.05 M treatment vs. 13,558 mg·kg−1 Na and 12,991 mg·kg−1 Cl in the 0 M treatment). This indicated potential for bioremediation of saline soil or hydroponic water. Concentrations of macronutrients such as nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), and sulfur (S) were reduced when plants received increasing NaCl treatments. In general, this study showed that growth of ice plant benefited from 0.05 and 0.10 M NaCl additions to the hydroponic nutrient solution. Ice plant deserves further work on its ability to reduce Na and Cl from accumulating in recirculating hydroponic nutrient solution.

Influence of the spectral composition of light on the morphogenesis of the epiphytic orchid <i>Cattleya labiata</i> Lindl. cultivated in the greenhouse

This work evaluates the test results of 3 types of LED lamps with different spectral composition of radiation and photon flux of photosynthesis (PPF, μmol/m2/sec): PPG T8I Agro (37), Navigator DSP-FITO (47.5) and DDP06-3×8-004 UHL 4 ‘Home Farm' (100), in the greenhouse culture of the orchid Cattleya labiata Lindl. The parameters of the thickness of annual leaves, the percentage of dry matter and the increase in biomass per unit of leaf surface (μg/cm2) formed over a period of 140 days were used as indicators to assess the degree of influence of the spectral composition of light on the morphogenesis of C. labiata plants. The spectral characteristics of the LED lamp DDP06-3×8-004 UHL 4 ‘Home Farm' with a white glow, intensity PPF 100 are considered as the most favorable for the successful greenhouse cultivation of the orchid Cattleya labiata Lindl. The combination in its spectrum of red and green spectra with their ratio equal to 1.3, and when the ratio of red and blue spectra equal to 3.34, a higher level of dry matter accumulation is observed per unit of leaf surface area white maintaining parameter of the leaf structure characteristic of a given plant species.

Determination of long distance transport of Cs+, Co2+ and Zn2+ ions in vascular plants by autoradiography and gamma-spectrometry

Heavy metals and radionuclides can enter the food chain via cereals and vegetables grown in contaminated soils. In the case of microelements such as zinc, studies have not focused only to assessing its environmental risk, but also to enhancing its uptake by plants as an important growth-limiting factor. In our study, digitalized autoradiograms of whole plants of celery (Apium graveolens L.), tobacco (Nicotiana tabacum L.) and sunflower (Helianthus annuus L.) grown in hydroponic nutrient media spiked with 137CsCl, 60CoCl2 and 65ZnCl2 were used for quantitative determination of uptake, long-distance transport and distribution of Cs+, Co2+ and Zn2+ ions in plant tissues. Results from autoradiography and gammaspectrometry of plants showed, that cesium was translocated to aboveground part of the plants with the shoot-to-root ratio 1.0 : 0.6. On the contrary, cobalt and zinc were more immobilized in roots, with the shoot-to-root ratio up to 1.0 : 3.8. The highest concentration of cesium, cobalt and zinc, expressed in specific radioactivity per unit of leaf surface (Bq/cm2) was found in top, rapidly growing leaves, the lowest concentration in the oldest leaves in low position. Detection limits 3, 2 and 14 Bq/cm2 by using X-ray film
 for 137Cs, 60Co and 65Zn, respectively were obtained. These data correspond to detection limits 10.5 pg Cs+/cm2, 7.2 pg Co2+/cm2 and 785 pg Zn2+/cm2 at specific radioactivity of commercially available 137CsCl, 60CoCl2 and 65ZnCl2. Resolutions 1-2 mm was sufficient for visualization of metal uptake and distribution in roots, stalks, leaves and leaf venation. Obtained data are part of quantitative study of uptake and translocation of both low level-radioactive contamination in plants and microelements applied as fertilizers.

Rainfall intensity plays an important role in the removal of PM from the leaf surfaces

Apparently, plant leaf surface particulate matter (PM) can be effectively removed by rainfall, leaving space on the leaf surface to adsorb and retain PM again. At present, most of the relevant studies adopt the method of artificial rainfall simulation to quantify rainfall characteristics in terms of rainfall intensity, and mostly focus on one category of plants. Studies of rainfall intensity on different categories of plants are lacking. Therefore, in this study, common urban greenery plants were classified into four categories, namely, trees, shrubs, herbs, and aquatic plants. Artificial rainfall was used and three different gradients of rainfall intensity, 30 mm/h, 45 mm/h and 60 mm/h, were set. The mass of per unit leaf area PM removal was calculated using the elution weighing method and the filter membrane method was used to classify the PM into three particle sizes: coarse (10–100-μm), fine (3–10-μm) and ultrafine (0.4–3-μm). It was devoted to investigating the differences in the effect of rainfall intensity on the removal of PM from the leaf surfaces of different categories of common urban greenery. The results showed that the removal of coarse particles by rainfall was the highest under different rainfall intensities. At the same time, the removal effects of rainfall on leaf surface PM of herbs were the highest under different rainfall intensity, while that of trees was the lowest. Among the same category of plants, Salix matsudana had better particle retention capacity among trees, Buxus sinica among shrubs, Poa pratensis among herbs, and Acorus calamus among aquatic plants. In addition, all tested plants had the highest mass of PM removed from leaf surface units at high rainfall intensity (60 mm/h). However, at a higher rainfall intensity (45 mm/h), the mass of PM on plant unit leaf surface removed was lower than the minimum rainfall intensity (30 mm/h). The results of the above study can provide a basis and theoretical support for the selection of species for urban green space restoration, as well as a reference for the establishment of urban cleaning systems from the perspective of the relationship between rainfall intensity and PM on plant leaf surfaces.

Effect of 6-Benzylaminopurine on Morphogenesis and Production Process of Sweet Pepper (Capsicum annuum L.)

Effect of 6-Benzylaminopurine on Morphogenesis and Production Process of Sweet Pepper (Capsicum annuum L.)

Spatial Modeling of Maximum Capacity Values of Irrecoverable Rainfall Retention by Forests in a Small Watershed

When performing hydrologic calculations, the actual amount of rain precipitation falling under the tree canopies of the taiga zone is one of the most important factors in forming and estimating rainfall runoff. This is due to the fact that only a portion of rainfall reaching the soil through the forest canopy takes part in forming river runoff. At present, there is no unanimity on methods of estimating rainfall retention by the canopies of different tree species in various natural geographical zones. The existing estimation methods rely on empirical observations of net and gross rainfall rather than on the results of physical modeling of moisture on leaf surfaces in droplet form. The disadvantages of the existing methods mean that it is not possible to make a spatial estimation of rainfall captured by canopies. The purpose of this study was to map the maximum rainfall interception capacity for a small forest watershed. The authors were able to solve the following problems: (1) In situ modeling of specific water retention in droplet form on leaf surfaces of tree species of the experimental watershed in the middle taiga subzone was carried out and the specific water retention per unit leaf area was determined. Such experiments have never been conducted previously. (2) Indirect methods of estimating the leaf surface area of tree plants depending on the amount of phytomass, age and height of tree stands were developed. (3) Mapping of tree stand characteristics (such as species composition, height, canopy cover) were performed, and together with the specific rainfall interception capacity, which was determined during experiments, provided the basis for a map of maximum rainfall retention capacity by canopies, i.e., a spatial image of irrecoverable rainfall losses was obtained. Rainfall is retained on a canopy in droplet form (droplet size varies from 10.6 to 18.6 mg). Specific water retention (mass per unit leaf surface area) is determined by the leaf (needle) roughness. The overall droplet retention on canopies is determined by leaf surface area and precipitation intensity. The maximum mass of the rainfall retained on the canopies of individual deciduous trees reaches 77 kg, (3.0–4.0 mm per canopy projection area) and that of coniferous trees ranges from 24.8 to 58.0 kg (1.9 to 5.9 mm). Understanding rainfall loss values in hydrology is of key importance in distributed models of rainfall flooding. Taking into account rainfall losses due to canopy interception makes it possible to reduce the margin of error in calculations of maximum rainfall flood loss from 126% to 25%.

How Does Water-Stressed Corn Respond to Potassium Nutrition? A Shoot-Root Scale Approach Study under Controlled Conditions

Potassium (K) is generally considered as being closely linked to plant water dynamics. Consequently, reinforcing K nutrition, which theoretically favors root growth and specific surface, extends leaf lifespan, and regulates stomatal functioning, is often used to tackle water stress. We designed a greenhouse pot-scale device to test these interactions on corn (Zea mays L.), and to analyze their links to plant transpiration. Three levels of K nutrition were combined with two water-supply treatments. Shoot and root development and growth were continuously measured during a 60-day-long experiment. Individual plant transpiration was measured by weighing pots and by calculating water mass balances. The results showed that, although K deficiency symptoms resembled those caused by water shortage, there was no advantage to over-fertilizing water-stressed plants. K failed to decrease either the transpiration per unit leaf surface or to improve water use efficiency. The link between K nutrition and plant transpiration appears solely attributable to the effect of K on leaf area. We conclude that K over-fertilization could ultimately jeopardize crops by enhancing early-stage water transpiration to the detriment of later developmental stages.

GENETIC RESOURCES OF ROOT VEGETABLES CROPS IN CENTRAL REGION OF RUSSIA

As a result of the research carried out in 2013-2016, the viability and originality of 1157 accessions of root vegetables have been preserved. 250 breeding accessions of carrot, beetroot and radish have been assessed for different economically valuable traits in open field and laboratory tests. Out of them, 65 accessions were selected out as sources of economically valuable traits. The early-maturing accessions of radish, such as ‘Korsar’, ‘Francuzsky Zavtrak’, ‘Mikhnevsky 1’, ‘18 Dney’, ‘Koroleva Margo’, ‘Polyna’, ‘Rozovo-Krasny s Belym Konchikom’, ‘Sofit’, ‘Kvarta’, ‘Saksa’, ‘Variant’ were regarded. The carrot accessions, such as ‘Scarlet’, ‘Koroleva Oseni’, ‘Dlinnaya Krasnaya’ were distinguished as sources of high yield capacity. The sources of high root yield in beetroot were varieties: ‘Valenta’, ‘Mestnaya iz Madagaskara’, Goldiers Super Black Beet, Zwaans Early Red Chief. The long shelf-life during wintertime was observed in beetroot varieties: ‘Slowiblot’, ‘Valenta’, ‘Lomarina’. The varieties: ‘Nevezhes’, ‘Neger Schwarz Halblange’, ‘Goldiers Super Black Beet’ were distinguished by high root marketability. With the use of world plant collection at VIR, the following varieties of root vegetables: ‘Dar Podmoskovya’ in carrot; ‘Osennya Princessa’ in beetroot; ‘Mikhnevskiy 1 ‘in garden radish; ‘Osenniy Krasavets’ in daikon; ‘Albina’ in root parsley; ‘Atlant’ in parsnip; Moscowskiy Krasavets in celery, and ‘Oseniya Udacha’ in wild radish were developed. It was also shown those varieties that had high yield capacity and root marketability were distinguished by small epidermal cell structure and large number of stomata per unit of leaf surface. It may be supposed that the large number of stomata per unit of leaf surface and small epidermal cell structure was the evidence of adaptive capacity of accessions taken for the study.

Genetic association of stomatal traits and yield in wheat grown in low rainfall environments.

BackgroundIn wheat, grain filling is closely related to flag leaf characteristics and function. Stomata are specialized leaf epidermal cells which regulate photosynthetic CO2 uptake and water loss by transpiration. Understanding the mechanisms controlling stomatal size, and their opening under drought, is critical to reduce plant water loss and maintain a high photosynthetic rate which ultimately leads to elevated yield. We applied a leaf imprinting method for rapid and non-destructive phenotyping to explore genetic variation and identify quantitative traits loci (QTL) for stomatal traits in wheat grown under greenhouse and field conditions.ResultsThe genetics of stomatal traits on the adaxial surface of the flag leaf was investigated using 146 double haploid lines derived from a cross between two Australian lines of Triticum aestivum, RAC875 and Kukri. The drought tolerant line RAC875 showed numerous small stomata in contrast to Kukri. Significant differences between the lines were observed for stomatal densitity and size related traits. A negative correlation was found between stomatal size and density, reflecting a compensatory relationship between these traits to maintain total pore area per unit leaf surface area. QTL were identified for stomatal traits on chromosomes 1A, 1B, 2B, and 7A under field and controlled conditions. Most importantly some of these loci overlap with QTL on chromosome 7A that control kernel number per spike, normalized difference vegetation index, harvest index and yield in the same population.ConclusionsIn this first study to decifer genetic relationships between wheat stomatal traits and yield in response to water deficit, no significant correlations were observed among yield and stomatal traits under field conditions. However we found some overlaps between QTL for stomatal traits and yield across environments. This suggested that stomatal traits could be an underlying mechanism increasing yield at specific loci and used as a proxy to track a target QTL in recombinant lines. This finding is a step-forward in understanding the function of these loci and identifying candidate genes to accelerate positional cloning of yield QTL in wheat under drought.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0838-9) contains supplementary material, which is available to authorized users.

Cluster shading effects on fruit quality, fruit skin color, and anthocyanin content and composition in Reliance 8 Vitis hybrid)

Water and photosynthetic functions on a plant scale were studied simultaneously on traditionally and lyre-shaped grapevines grown in field conditions. The study was carried out on Cabernet Sauvignon/101-14 planted in gravelly soil. Observations concerning the water behavior (leaf water potential, transpiration per leaf surface unit) of both training systems used indicate that the traditional vine manifests a better water status when compared with the lyre-shaped vine. The difference is in agreement with net photosynthesis values per leaf surface unit, clearly superior on the traditional vine. It seems, however, that the existence of a greater leaf surface per soil surface in the lyre-shaped vine compensates the reduction in photosynthesis per leaf surface. The compensation results in very close agronomical yield for both training systems. The main conclusion of this study is that a water constraint having a diminishing effect on net photosynthesis can, on the other hand, have favorable consequences on the elaboration of qualitative criteria, in particular, the synthesis of polyphenols.

Foliar rinse study of atmospheric black carbon deposition to leaves of konara oak (Quercus serrata) stands

Dry deposition of Black Carbon (BC) to the actual leaves of konara oak (Quercus serrata) was evaluated in a foliar rinse method in an experimental forest in the suburbs of Tokyo, Japan in order to explore deposition levels and vertical profile within the forest. At three heights of the forest of 20 m height, 20 m, 15 m, and 6 m or 4 m, leaves were sampled on a weekly basis for a couple of months in 2011 and 2012 and subjected to rinsing with water and chloroform. The BC in the rinse solution was collected on a quartz fiber filter and determined by spectrophotometry. The BC mass deposited to leaves increased with height and this profile pattern was generally maintained in the study period. The specific BC mass deposited to leaves showed considerable fluctuations with time, but the deposited BC increased rapidly with time in the bud flushing stage, then attained to a plateau, and began to decrease as the defoliation advanced. The plateau is a result of a simple accumulation with time and occasional removal due to rainfall and strong winds. The maximum BC mass deposited to leaves per leaf surface unit area occurred in June where the level was 10–15 mg-BC m−2. The rate of BC mass deposited to leaves at the time of leaves growing was determined to be 0.237 and 0.277 mg-BC m−2 day−1 for measurements in 2011 and 2012, respectively. On the basis of the observed BC mass deposited to the leaves, BC mass deposited to leaves per forest floor unit area estimated with LAI showed a strong seasonality. The BC mass deposited to leaves per forest floor unit area was compared to the deposition flux from the atmosphere to the forest canopy, which would be interpreted as indicating that 30% of atmospheric BC deposition to the canopy was retained on the leaves in time of leaves growing.

A MODIS-based perpendicular moisture index to retrieve leaf moisture content of forest canopies

Moisture dictates vegetation susceptibility to fire ignition and propagation. Various spectral indices have been proposed for the estimation of equivalent water thickness (EWT), which is defined as the mass of liquid water per unit of leaf surface. However, fire models use live fuel moisture content (LFMC) as a measure of vegetation moisture. LFMC is defined as the ratio of the mass of the liquid water in a leaf over the mass of dry matter, and traditional spectral indices are not as effective as with EWT in capturing LFMC variability. The aim of this research was to explore the potential of the Moderate Resolution Imaging Spectroradiometer (MODIS) on board Terra and Aqua satellites in retrieving LFMC from top of the canopy reflectance, and to develop a new spectral index sensitive to this parameter. All the analyses were based on synthetic canopy spectra constructed by coupling the PROSPECT (leaf optical properties model) and SAIL (Scattering by Arbitrarily Inclined Leaves) radiative transfer models. Simulated top of the canopy spectra were then convolved to MODIS ‘land’ channels 1–7 spectral response functions. All band pairs were evaluated to determine the subspace of MODIS measurements where the separability of points based on their value of LFMC was the highest. This led to the identification of isolines of LFMC in the plane defined by MODIS reflectance measurements in channels 2 and 5; the isolines are straight and parallel, and ordered from lower to higher values of LFMC. This observation allowed the construction of a novel spectral index that is directly related to LFMC – the perpendicular moisture index (PMI). This index measures the distance of a point in the plane spanned by reflectance measurements in MODIS channels 2 and 5 from a reference line, that of completely dry vegetation. Validation against simulated data showed that PMI exhibits a linear relationship with LFMC. When the vegetation cover is dense, the LFMC explains most of the variability in the PMI (R2 = 0.70 when LAI > 2; R2 = 0.87 when LAI > 4). When the LAI is lower, the contribution of soil background to the measured reflectance increases, and the index underestimates LFMC. The PMI was also validated against the LOPEX93 (Leaf Optical Properties Experiment 1993) data set of leaf optical and biophysical measurements, scaled to canopy reflectance with SAIL, showing acceptable results (R2 = 0.56 when LAI > 2; R2 = 0.63 when LAI > 4).

Late harvest associated with P and S fertilization enhances yield and quality of forage sorghum (Sorghum bicolor (L.) Moench), grown as a rainfed crop in Pakistan

-1 ), in combination with three levels of sulphur (0, 20 and 40 kg SO 4 ha -1 ), in combination with three harvest times (35, 45 and 55 days after emergence; DAE), were tested in a factorial randomized block design. At each harvest, morphological, functional, yield and quality traits were assessed on plant samples. Extending the growing season from DAE 35 to 55 enhanced almost all the traits and greatly benefited dry biomass yield (ca. +100%). The longer growth also determined a higher efficiency in the accumulation of dry biomass per unit time and land surface (crop growth rate ca. +30%), as well as per unit time and leaf surface (net assimilation rate ca. +100%). Quality traits also improved when plants were harvested at a more advanced maturity: leaf hydrocyanic acid content, a toxic component to livestock, decreased by ca. 30%; stalk soluble-solid content, an indicator of forage juiciness and palatability, increased by ca. 50%. On concluding, the combined effects of harvest delay, P and S fertilization on sorghum are deemed able to significantly increase forage production in warm, relatively dry areas of the world.

Salt tolerance analysis of Arabidopsis thaliana NOK2 accession under saline conditions and potassium supply

The response to salt treatment and K+ provision of two Arabidopsis thaliana accessions grown for 17 days in the presence of 50 mM NaCl was investigated. Leaf and root dry weight deposition was restricted by salt, more in Col accession than in NOK2 accession. In both accessions, the growth inhibition induced by salinity was associated with a decrease in total leaf surface area, which resulted from diminished leaf number, but not from restriction of individual leaf surface area. Comparing the effects of salt on dry matter production and total leaf surface area revealed large difference between Col and NOK2 for net assimilation rate (the amount of whole plant biomass produced per unit leaf surface area), which was augmented by salt and K+ in NOK2 but not in Col. This result, which suggested a better capacity of NOK2 to preserve its photosynthetic machinery against salt stress, was in agreement with the effect of NaCl on photosynthetic pigments. Indeed, salt significantly reduced chlorophyll and carotenoid content in Col leaves but had no impact on NOK2 leaf pigment content. Since K+ provision had only marginal effects on these responses to salt stress, leaf mineral unbalance was unlikely. Guaiacol peroxidase activity was augmented by salt treatment in leaves and roots of both accessions. Salinity decreased the catalase activity in Col leaves and in roots, and increased this activity in NOK2 organs. In conclusion, when aggressed by salt, NOK2 was able (1) to produce more leaves than Col, and (2) to efficiently protect its photosynthetic apparatus, perhaps by developing more efficient antioxidative defense through increased catalase and peroxidase activities. Consequently, the overall photosynthetic activity was higher and more robust to salt aggression in NOK2 than in Col.

Analysis of salinity effects on basil leaf surface area, photosynthetic activity, and growth

Basil (Ocimum basilicum L.) seedlings were cultured on liquid medium in controlled conditions. Two varieties differing in leaf size were compared. When plants were 30 days old, the medium was supplemented with 50 mM NaCl. After 15 days of treatment, root, stem and leaf biomass, leaf number, and leaf surface area were measured. Ion accumulation was determined in roots, stems, and leaves. Photosynthetic parameters (CO2 fixation rate, internal CO2 concentration, stomatal conductance) as well as transpiration rate were determined on separate leaves. Electrolyte leakage and malondialdehyde content were used to estimate damage to membranes and lipid peroxidation, respectively. Several antioxidant enzymatic activities were used as proxies of oxidative stress. High Na+ concentration was reached in leaf tissues. Salt restricted whole plant biomass deposition rate by diminishing leaf number and leaf expansion, as well as photosynthetic activity were estimated from whole plant biomass production per unit leaf surface area. Diminished stomatal conductance restricted CO2 fixation rate, and decrease in chlorophyll content presumably limited photosynthetic activity. Lipid peroxidation revealed damages to membranes. The magnitude of these responses differed between the two varieties, indicating that an intraspecific variability in salt response exists in basil.

Influence of nitrate—ammonium ratio on growth and nutrition of Arabidopsis thaliana

Arabidopsis thaliana seedlings were grown in hydroponic culture under controlled conditions in mediums with different NO 3 − /NH 4 + ratios. The mediums were not buffered, against pH change, but their pH was reset at pH 5.5 each 2 days. When ammoniacal N source was predominant, the whole plant biomass deposition was diminished, parallely to several parameters which revealed degraded leaf physiological status, such as leaf chlorosis associated with diminished chlorophyll content, lowered K+, Ca2+, and water content, along with restricted leaf expansion, and apparition of cellular stress symptoms. However, leaf functioning for biomass production did not seem affected, since biomass production rate per unit leaf surface area remained unchanged. Indeed, the main factor of decrease biomass production was leaf elimination and/or repression of leaf initiation. The results are discussed in the context of literature data on the effects of NH 4 + on ion fluxes at the root level and properties of K+ transport systems in Arabidopsis. Disturbance of mineral (cationic) nutrition by NH 4 + seemed to be a major cause of the detrimental effect of ammoniacal nutrition.