Tissue Nutrient Concentrations Research Articles

Effects of varying levels of nitrogen on plant growth, anti-Fusarium oxysporum activity and 3,5-dicaffeoylquinic acid concentration of extracts from hydroponically cultivated Helichrysum cymosum (L.)

Experiments were conducted to assess the effects of varied nitrogen (N) concentrations on plant growth, tissue nutrient content, and antimicrobial activity of acetone extract of aerial parts of Helichrysum cymosum. Six weeks old rooted cuttings were treated with 52.5, 105.0, 210.0, and 420.0 mg N/L by varying the nutrient N level in plant growth medium. Plant growth parameters, leaf tissue nutrient content, anti-Fusarium oxysporum activity, and a well-known bioactive secondary metabolite (3,5-dicaffeoylquinic acid) concentration in the plant extracts were analysed. Leaf number increased with increasing N level, while height increase was highest at the lowest N treatment. Tissue analysis of N content and LC-MS analysis of the acetone extracts of aerial parts indicated that lower N treatment corresponded to lower tissue N and higher accumulation of 3,5dicaffeoylquinic acid in the extracts, respectively. In conclusion, lower nutrient N level significantly correlated with increased antimicrobial activity and yield of the targeted compound of the crude acetone extract of H. cymosum. This study suggests that nitrogen fertilization may be manipulated to optimize bioactivities of crude extracts of medicinal plants.

English

Determination of nutrient contents is important as it provides theoretical and technical support for tending of the Chinese Fir plantation. In this study, dynamic changes in plant nutrient content in Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantations at different ages were studied. Data on continuous positioning were obtained from a Shangpuzi Woodland Ridge in Suining, Hunan province, China. The results showed that at the same age, different organs of Chinese fir possessed different nutrient content in the following order: needle > twig >bark > root > trunk. The order of each nutrient element was Ca > N > K > Mg > P in bark and root, N > Mg > Ca > K > P in trunk, and Ca > K > N > Mg > P in twig. The nutrient content of plant organs was highest in fast-growing (7 to 12-year old) period, and began to decline when entering the trunk wood stage, though the downward trend differed. The nutrient content in the same organs differed amongst plants of different ages. The variationin nutrient content in the undergrowth vegetation with forest age was comparable to that in the tree layer, whilst the content in the organs exceeded that of the corresponding organs of the tree layer. Upon comparison to the living tree layer, the nutrient content in plant tissues at different growth stages were determinednot only by the genetic and physiological characteristics of the plant itself, but further influenced by temperature, precipitation and other habitat conditions.© 2021Friends Science Publishers

Recycling Nutrient Solution Can Reduce Growth Due to Nutrient Deficiencies in Hydroponic Production.

It is common in hydroponics to supply nutrients to crops by maintaining electrical conductivity (EC) of the recycling solution at a target level. Levels of individual nutrients in the solution are generally not assessed as their regular measurement and adjustment can be both expensive and technically challenging. However, the approach of growing crops at a target EC can potentially result in nutrient imbalances in the solution and reduced growth. We quantified the effects of recycling on solution EC changes, tissue nutrient concentration, canopy growth rate, plant water status, and shoot and root weight of lettuce (Lactuca sativa) in a greenhouse. The tap water quality was moderately alkaline and similar to that commonly observed in many commercial greenhouses. In our research, recycling solution maintained at a target EC (1.8 dS⋅m–1) significantly reduced shoot fresh (22–36%) and dry weight compared to the control supplied regularly with freshly prepared solution at the target EC. Further, recycling significantly decreased N, P, K, and Fe and increased Na and Cu levels in the tissue, in addition to increasing solution EC between adjustments compared to the control. Using image analysis of groups of plants, we identified that the negative effects of recycling on canopy area started 2 weeks after transplanting. Based on these results, we hypothesized that certain unwanted compounds (e.g., bicarbonates) and slowly consumed elements (e.g., Ca, Mg) were added to the recycling solution through the alkaline tap water with time. Their accumulation “artificially” increased solution EC and “masked” the lower than optimal levels of major nutrients in the solution, leading to the reductions in the concentration of nutrients in the tissue and plant growth. Supporting this, the negative effects of recycling were not observed when the recycling solution was either discarded after 2 weeks of use or made using reverse osmosis water and continuously used. Our findings aid in proper management of recycling solution in hydroponic lettuce production.

Suitability of Wild Phragmites australis as Bio-Resource: Tissue Quality and Morphology of Populations from Three Continents

We collected and analyzed morphological characteristics and tissue nutrient concentrations of common reed (Phragmites australis) populations from Denmark, USA, and China, harvested late summer at the peak of the biomass production. The aim was to estimate the suitability of the biomass for different bioenergy purposes. The potential of reed as bioenergy feedstock is increasingly recognized, as the species already is utilized for construction, water purification, and pulp production. Our morphological data showed that biomass yield can be allometrically predicted to be high, especially in the reed populations of the US. However, no consistent pattern according to geographical origin was detected, and especially tissue nutrient concentrations varied within and between populations. Some mineral concentrations were above the desirable threshold for biocombustion, such as nitrogen (N) and sulfur (S). Iron (Fe) was higher than the critical toxicity concentration in many populations and hence, negatively correlated with morphological and growth traits. A different harvest time is likely to result in lower ion concentrations. Some populations had low C to N ratios, which are suitable for biomethane production, while the relatively low ash content of all populations (ranging from 3.9% to 8.5%) suggested a high heating value and theoretical energy potential. Reed biomass production is a promising alternative to fossil fuels and potentially suitable for other bio-based product. Improved knowledge is needed to examine local needs and application possibilities for reed biomass.

Supplementary Blue and Red LED Narrowband Wavelengths Improve Biomass Yield and Nutrient Uptake in Hydroponically Grown Basil

Light emitting diodes (LEDs) can produce a wide range of narrowband wavelengths with varying intensities. Previous studies have demonstrated that supplemental blue (B) and red (R) wavelengths from LEDs impact plant development, physiology, and morphology. High-pressure sodium (HPS) lighting systems are commonly used in greenhouse production, but LEDs have gained popularity in recent years because of their improved energy efficiency and spectral control. Research is needed to determine the efficacy of supplementary B and R LED narrowband wavelengths compared with traditional lighting systems like HPS in terms of yield, quality, and energy consumption for a variety of greenhouse-grown high-value specialty crops. The objective of this study was to determine the impact of LED and HPS lighting on greenhouse hydroponic basil (Ocimum basilicum var. ‘Genovese’) biomass production and edible tissue nutrient concentrations across different growing seasons. Basil was chosen because of its high demand and value among restaurants and professional chefs. A total of eight treatments were used: one nonsupplemented natural light (NL) control; one HPS treatment; and six LED treatments (peaked at 447 nm/627 nm, ±20 nm) with progressive B/R ratios (10B/90R; 20B/80R; 30B/70R; 40B/60R; 50B/50R; and 60B/40R). Each supplemented light (SL) treatment provided 8.64 mol·m−2·d−1 (100 µmol·m−2·s−1, 24 h·d−1). The daily light integral (DLI) of the NL control averaged 9.5 mol·m−2·d−1 across all growing seasons (ranging from 4 to 18 mol·m−2·d−1). Relative humidity averaged 50%, with day/night temperatures averaging 27.4 °C/21.8 °C, respectively. LED treatments had the greatest total fresh biomass (FM) and dry biomass (DM) accumulation; biomass for LED treatments were 1.3 times greater on average than HPS, and 2 times greater than the NL control. Biomass partitioning revealed that the LED treatments had more FM and DM for the individual main stem, shoots, and leaves of each plant at varying levels. LED treatments resulted in greater height and main stem diameter. Some essential nutrient concentrations were impacted by SL treatments and growing season. An energy analysis revealed that on average, narrowband B/R LED treatments were 3 times more energy efficient at increasing biomass over HPS. LED treatments reduced SL energy cost per gram FM increase by 95% to 98% when compared with HPS. In addition, the rate of electricity consumption to biomass increase varied across LED treatments, which demonstrates that basil uses different B/R narrowband ratios at varying efficiencies. This experiment shows that spectral quality of both supplemental sources and natural sunlight impacts primary metabolic resource partitioning of basil. The application of LED lighting systems to supplement natural DLI and spectra during unfavorable growing seasons has the potential to increase overall biomass accumulation and nutrient concentrations in a variety of high-value specialty crops.

Yield and nitrogen balance in corn grown under no-tillage system

ABSTRACT The corn crop is highly responsive to nitrogen fertilization; however, the application of high doses generally causes a reduction in the use efficiency of fertilizer. In this sense, this study aimed to determine the yield and nitrogen balance in corn grown under the no-tillage system. The experiment consisted of the application of four nitrogen doses (0, 30; 70 and 95 kg ha-1). In all plots with the AG 1051 hybrid corn, 80 and 56 kg ha-1 of P2O5 and K2O were applied, respectively. The experiment was arranged in a randomized block design with five replications. The grain yield had a linear increasing behavior according to the nitrogen doses, which reached 5,684.79 kg ha-1. The fertilization efficiency and the N extraction increased linearly with the increase of the nitrogen doses, obtaining with the highest dose the extraction of 114.93 kg ha-1 of N and a fertilization efficiency of 65%. The soil N stock of 4,489 kg ha-1 provides corn plants with 52.81 kg ha-1 of this nutrient. Corn adjusts the biomass production according to the availability of nitrogen, with no effect of N doses on the nutrient content in plant tissues.

A Decade of Ecosystem-Scale Research at an Aridland Constructed Treatment Wetland

Cities are increasingly pursuing more resilient and sustainable futures. One way to do so is by the increased use of Urban Ecological Infrastructure (UEI), including constructed treatment wetlands (CTW). This strategy is particularly important for aridland cities with scarce water resources. In this paper I synthesize nearly ten years of systems-level research at the Tres Rios CTW in Phoenix, AZ USA. Since July 2011, a research team that includes dozens of student volunteers has been sampling monthly for herbaceous biomass and productivity, water quality, transpiration rates, and aquatic metabolism. We also quantify belowground biomass and plant tissue nutrient content annually, and measured greenhouse gas fluxes from 2012 - 2014. Our peak summer biomass values are among the highest reported in the literature, and high rates of transpiration are associated with this biomass. Using our whole-system water budgets and tracer studies we have documented a slow movement of surface water into the marsh from adjacent open water areas that is driven by transpirational losses and that we refer to as the “biological tide”. With our nitrogen (N) budgets for the whole system and the vegetated marsh we showed that roughly 50% of the annual N uptake by the vegetated marsh is driven by new water entering via this biological tide. Our aquatic metabolism sampling suggested that the N uptake associated with the autotrophic water column was roughly 27% of the average annual N uptake by the vegetated marsh. The marsh is a source of CH4 and N2O across the air-water interface and the plants are a net source of CH4 but a net sink for N2O. Our combined flux estimates suggest that the Tres Rios marshes are a net sink for greenhouse gas equivalents because of this plant-mediated net uptake of N2O. Finally, over the years our Tres Rios CTW project has provided a platform for dozens of students and young people to experience ecological research, both in the field and in the lab.

Motorway age is linked to larger body size, but not song carrier frequency, in male grasshoppers from roadside populations

Producing calls with increased minimum carrier frequency is well documented in sound communicating species confronted with noise pollution, possibly helping them to avoid acoustic masking of low-frequency signals. However, the lack of studies on invertebrates limits our understanding of the potentially adverse effects of anthropogenic noise on natural populations. While males of the grasshopper Chorthippus biguttulus are known to produce courtship signals with elevated low-frequency local maxima (LFLM) in roadside populations, previous studies provided no insight into morphological traits underlying LFLM shifts. Although developmental plasticity was identified as one main factor accounting for elevated LFLM, an additional role for a more hard-wired trait architecture was proposed, possibly as a result of adaptation to traffic noise. Our current study therefore aims to assess (1) whether the position of LFLM is related to male body size, (2) whether body size is correlated with motorway age, and (3) whether the position of LFLM is correlated with motorway age in C. biguttulus males from roadside populations. In addition to substantial variation in LFLM among C. biguttulus males, we found that larger males produced signals with lower LFLM, suggesting a potential role in female choice as a predictor of male quality. While we found no significant correlation between LFLM and motorway age, C. biguttulus males were larger near older motorway sections. This positive correlation may be due to several reasons, including: (1) higher nutrient concentration and availability in plant tissues due to eutrophication of roadside habitats; (2) temporal succession of male size phenotypes during colonization processes; and/or (3) selection for larger body size in roadside populations. Our results highlight the multifaceted and often complex nature of the relationships between morphology, signal traits and anthropogenic pressures on sound communication in invertebrates.

Defining Optimal Strength of the Nutrient Solution for Soilless Cultivation of Saffron in the Mediterranean

Saffron is traditionally cultivated in soil as a semi-perennial crop, although the feasibility of crop production is today constrained in Europe due to both agronomic and socioeconomic factors. Accordingly, interest has been increasing concerning its possible cultivation within protected environments through adoption of soilless cultivation technologies. The aim of the present study was to optimize nutrient solution features in the soilless cultivation of saffron corms. The trial was conducted in a greenhouse at Almeria University. Saffron was grown in 15-L pots filled with perlite. Three fertigation treatments were used, obtained by a linear increase of all nutrients of one standard in order to reach an electrical conductivity (EC) of 2.0 (control, EC2.0), 2.5 (EC2.5) and 3.0 (EC3.0) dS·m−1. Measurements included determinations of shoot length, corm yield, as well as nutrient uptake from the nutrient solution and concentrations within plant tissues. The nutrient solution with the highest EC (EC3.0) allowed obtaining three to five times more corms above 25-mm diameter. The increasing EC had a significant effect on the increase of macronutrient uptake, except for NO3− and NH4+ and resulted in a general increase of nutrient concentrations in tissues, such as corms and roots. Both macronutrient uptake and accumulation in plant tissues were highest under EC3.0. Nutrient uptake was significantly correlated with production of larger corms due to higher horizontal diameter.

Interactive Effects of N Form and P Concentration on Growth and Tissue Composition of Hybrid Napier Grass (Pennisetum purpureum × Pennisetum americanum).

This study aimed to assess effect of nitrogen (N) form and phosphorus (P) level on the growth and mineral composition of hybrid Napier grass. Experimental plants were grown with different N forms (NO3−, NH4NO3, and NH4+; 500 µM) and P concentrations (100 and 500 µM) under greenhouse conditions for 42 days. Growth rate, morphology, pigments, and mineral nutrients in the plant tissue were analysed. At the low P concentration, the better growth was found in the plants supplied with NH4+ (relative growth rate (RGR) = 0.05 g·g−1·d−1), but at the high P concentration, the NH4+-fed plants had 37% lower growth rates and shorter roots and stems. At the high P level, the NH4NO3−-fed plants had the highest RGR (0.04 g·g−1·d−1). The mineral nutrient concentrations in the plant tissues were only slightly affected by N form and P concentration, although the P concentrations in the plant tissue of the NO3−-fed plants supplied with the high P concentration was 26% higher compared to the low P concentration plants. The N concentrations in the plant tissues did not vary between treatments. The results showed that the optimum N form for the plant growth and biomass productivity of hybrid Napier grass depends on P level. Hybrid Napier grass may be irrigated by treated wastewater containing high concentrations of N and P, but future studies are needed to evaluate biomass production and composition when irrigating with real wastewater from animal farms.

Storage capacity for phosphorus during growth and maturation in a brown alga Sargassum macrocarpum

Improved coastal management has decreased anthropogenic nutrient input over the past few decades, leading to phosphorus depletion. It has been hypothesized that phosphorus depletion in coastal environments leads to declines in macroalgae abundance. Perennial canopy-forming temperate macroalgae can experience the effects of limited phosphorus availability during seasonal phosphorus depletion periods. When nutrients are sufficient, they are stored in algal tissues after luxury uptake and are available to support growth during phosphorus-depleted conditions. Cultivation of mature and actively growing juvenile brown alga (Sargassum macrocarpum) under different nutrient conditions provided individuals with different tissue nutrient concentrations. The maximum photosynthetic rates of these individuals were examined under nutrient-depleted conditions to evaluate “storage capacity”, which we defined as the amount of stored phosphorus that can support maximum growth. Maximum photosynthetic rate was used as a proxy for maximum growth rates. The experiments revealed that growth rates of juveniles increased when stored phosphorus content was high. In contrast, the maximum growth rates tended not to increase with an increase in stored phosphorus content in mature individuals. The phosphorus storage capacities for juvenile and mature individuals were approximately 19 and more than 16 weeks, respectively, suggesting that individual alga can endure several months of phosphorus depletion.

Low phosphorus supply constrains plant responses to elevated CO2 : A meta-analysis.

Phosphorus (P) is an essential macro-nutrient required for plant metabolism and growth. Low P availability could potentially limit plant responses to elevated carbon dioxide (eCO2 ), but consensus has yet to be reached on the extent of this limitation. Here, based on data from experiments that manipulated both CO2 and P for young individuals of woody and non-woody species, we present a meta-analysis of P limitation impacts on plant growth, physiological, and morphological response to eCO2 . We show that low P availability attenuated plant photosynthetic response to eCO2 by approximately one-quarter, leading to a reduced, but still positive photosynthetic response to eCO2 compared to those under high P availability. Furthermore, low P limited plant aboveground, belowground, and total biomass responses to eCO2 , by 14.7%, 14.3%, and 12.4%, respectively, equivalent to an approximate halving of the eCO2 responses observed under high P availability. In comparison, low P availability did not significantly alter the eCO2 -induced changes in plant tissue nutrient concentration, suggesting tissue nutrient flexibility is an important mechanism allowing biomass response to eCO2 under low P availability. Low P significantly reduced the eCO2 -induced increase in leaf area by 14.3%, mirroring the aboveground biomass response, but low P did not affect the eCO2 -induced increase in root length. Woody plants exhibited stronger attenuation effect of low P on aboveground biomass response to eCO2 than non-woody plants, while plants with different mycorrhizal associations showed similar responses to low P and eCO2 interaction. This meta-analysis highlights crucial data gaps in capturing plant responses to eCO2 and low P availability. Field-based experiments with longer-term exposure of both CO2 and P manipulations are critically needed to provide ecosystem-scale understanding. Taken together, our results provide a quantitative baseline to constrain model-based hypotheses of plant responses to eCO2 under P limitation, thereby improving projections of future global change impacts.

Nutrient Diagnosis Norms for Date Palm (Phoenix dactylifera L.) in Tunisian Oases

Several studies have pointed out the promising use of nutritional diagnosis methods for the determination of optimum nutrient contents in plant tissues. The present investigation was carried out in different oases in Southern Tunisia to determine reference values for the interpretation of leaf analyses of date palm (Phoenix dactylifera) Deglet Nour cultivar with the Critical Value Approach (CVA) and the Compositional Nutrient Diagnosis (CND). A database (n = 100) of yield and mineral concentrations taken from date palm leaflets in October, at the maturity stage of dates, was used. The yield cut-off between low-yield and high-yield subpopulations, selected from cumulative variance ratio functions across survey data, was 76 kg palm−1 and the global nutrient imbalance index (CNDr2) was 10.06. Critical CND nutrient indices were found to be symmetrical around zero as follows: (1.59; +1.59) for IN, (−0.44, +0.44) for IP, (−0.63, +0.63) for IK, (−0.94, +0.94) for ICa, (−1.05, +1.05) for IMg, (−0.80, +0.80) for IFe, (−0.74, +0.74) for ICu, (−0.80, +0.80) for IB, (−0.93, +0.93) for IZn, (−1.04, +1.04) for IMn, and (−1.03, +1.03) for the residual value. Compared to CND, the CVA approach shows weak detection of the nutrients that cause nutritional imbalance. CND indices revealed, except for N, the presence of nutrient imbalances and the necessity to correct the mineral nutrition of date palm in the Kebeli oases.

Influence of nutrient solution concentration on growth and tissue mineral content of Panax ginseng seedlings cultured in a root medium containing peat and perlite

There is an increasing trend of producing seedlings of Panax ginseng in amended root media in raised beds. Precise control of the fertility of root media is essential for raising healthy seedlings, especially when inert media with a low buffering capacity are used. The objective of this study was to investigate the influence of fertility (as measured by EC) of the nutrient solution used for seedling production. One thousand eight hundred seeds were sown for five treatments and a control (300 seeds per treatment, 3 × 3 cm spacing) using root medium [composed of peat moss + perlite (7:3, v/v)] on raised beds with measurements, 120 × 60 × 25 cm (L × W × H) on Mar 9, 2018. Five nutrient solutions with different strengths (0.4, 0.6, 0.8, 1.0, 1.2 dS m−1 EC) were prepared with ground water (0.25 dS m−1) and a fertilizer stock solution (2 mM NH4+-N, 12 mM NO3−-N, 1 mM H2PO4−, 8 mM K+, 2 mM Ca2+, 1 mM Mg2+, 1 mM SO42−). Fertigation of the beds started on May 21 using each of six nutrient solutions and fertigation frequencies were controlled using an EC5 soil moisture sensor. The stock solutions were automatically supplied for 30 min when the volumetric water content decreased to 36%. Plant growth measurement and soil analyses were carried out twice: first at 144 days and subsequently at 197 days (from the day of seeds sown). For the first growth measurement, elevated EC in the fertilizer solution resulted in enhanced growth, but statistical differences among treatment solutions were not significant except for the case of ground water. In the second measurement, the seedling growth in terms of dry weight of above- and below-ground plant parts increased significantly in plants treated with the 1.0 dS m−1 EC solution and decreased in plants treated with the (1.2 dS m−1 EC) solution. In both the first and second measurements, the ground tissue nutrient content (T-N, P, K and Ca) was significantly different among treatments. The EC of root media in the case of 1.0 dS m−1 treatment, where the seedling growth was the highest among treatments, was 0.54 dS m−1 at the first measurement and 0.82 dS m−1 at the second measurement. In summary, a root medium with a mixture of peat moss + perlite (7:3, v/v), a leaching percentage of 20–30%, and a nutrient solution with a concentration of 1.0 dS m−1 EC is suitable for the healthy growth of ginseng seedlings.

Do soil test levels and fertilization with phosphorus and potassium impact field crop tissue concentrations?

AbstractSoil testing and plant tissue nutrient concentrations form the basis for fertilizer recommendations in Ohio. The response of crop phosphorus (P) and potassium (K) nutrient concentrations to soil test levels and fertilizer applications influences fertilizer recommendations but have not been rigorously evaluated in this region. The objective of our study was to determine the effects of (a) soil test P and K levels and (b) P and K fertilization on mid‐season leaf and grain P and K concentrations of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.). From 2014–2018, we conducted 186 on‐farm trials (99 P, 87 K trials) over a diversity of soil types, crop genetics, and management histories in 39 counties throughout Ohio. Soil test P and K levels, mid‐season leaf P and K concentrations, and grain P and K concentrations were measured on randomized and replicated plots. Both leaf and grain nutrient concentrations generally increased with the soil test levels, but the relationships were weak in all three crops. Fertilization of P and K marginally but consistently increased leaf tissue concentrations in all crops but had a lesser effect on grain P and K concentrations. Our data suggest that current sufficiency ranges for corn, soybean, and wheat are too high and need revision. Collectively, our results show that crop P and K tissue concentrations are positively, but weakly related to soil test levels and fertilization, and this information has important implications for future development of nutrient management frameworks in Ohio.

Assessment of soil fertility and potato crop nutrient status in central and eastern highlands of Kenya

Inherent low soil fertility remains a hindrance to potato production in Kenya and continues to pose a threat to food security. A study was conducted in Nyandarua and Meru counties to assess the soil fertility status in smallholder potato farms. Soil and plant tissue samples were collected and analysed for selected nutrients (pH, OC, N, P, K, S, Ca, Mg, Zn, B and Cu) from 198 farms. Critical nutrient levels were used to assess the sufficiency levels of nutrients for potato growth. Soils in the sampled farms were weakly to strongly acidic (pH-CaCl2 3.9–6.6) and had low to high soil organic matter content (1.5–97.5 g Kg−1). The percent of farms in Meru and Nyandarua with nutrient contents below critical levels were 66% and 20% for N, 46% and 85% for P, 67% and 31% for S, 9% and 51% for Cu, and 87% and 80% for B, respectively. Low tissue nutrient concentrations were observed for N, P, K, and S irrespective of the sites. Soil pH correlated strongly with majority of the analyzed soil and tissue nutrients. These results affirm the need to design integrative soil fertility management strategies to correct the impoverished soil fertility status in the study area.

Effects of light intensities and varying watering intervals on growth, tissue nutrient content and antifungal activity of hydroponic cultivated Tulbaghia violacea L. under greenhouse conditions

Optimization of the quality and quantity of medicinal materials during cultivation could improve the value of medicinal plants. Light intensity and water availability affect physiological processes and growth of plants. Tulbaghia violacea L. (Alliaceae) bulbs and leaves are widely used traditionally in southern Africa for treatments of many ailments. The interactive effects of light intensity and watering regime on plant growth, nutrient uptake and antifungal activity of T. violacea were evaluated in the current study. Seedlings of T. violacea were grown hydroponically under two shading levels (0% and 40%) while being exposed simultaneously to one of three watering intervals: 5-day, 14-day and 21-day. Different growth parameters (plant height, plant fresh and dry weights) and tissue nutrient contents were evaluated at the end of the experiment. The antifungal activity of acetone extracts on Fusarium oxysporum were evaluated in a microdilution bioassay. Generally, significantly higher concentrations of macronutrients were recorded in the tissue of plants exposed to shorter watering interval. The results showed that different watering frequencies and light intensities significantly (p < 0.05) influenced plant growth parameters (height, and dry and fresh weights). Moreover, there were strong interactive effects of watering frequency and light intensity on most of the plant growth parameters. Remarkably, plants that were simultaneously exposed to the extended watering interval (21-day) and low light intensity showed the best anti-F. oxysporum activity. Key findings of this study revealed that shading alleviated the negative effects of water-deficit stress on plant growth and improved antifungal activity.

Performance of Cyperus papyrus in constructed wetland mesocosms under different levels of salinity

Constructed wetlands (CWs) are consolidated technologies used for removing organic matter (OM) and nutrients (nitrogen (N) and phosphorus (P)) from wastewater. Recently, these systems have been implemented for treating wastewater under saline conditions. In this context, the aim of this study was to evaluate the effect of wastewater with different levels of salinity, expressed as electrical conductivity (EC), on the removal efficiencies of OM and on the growth of vegetation planted in CW mesocosms. For this, five horizontal subsurface flow constructed wetlands (HSSFs) planted with Cyperus papyrus were operated under different salinity levels: 1 (CW-C), 2.5 (CW-2.5), 5 (CW-5), 7.5 (CW-7.5) and 10 mS/cm (CW-10) using CW-C as a control system. To analyze the effects of different salinity levels, the removal efficiencies of chemical oxygen demand (COD) and biological oxygen demand (BOD5) were evaluated. Moreover, the growth characteristics of Cyperus papyrus were compared in the different CWs through the determination of chlorophyll concentration and nutrient contents in different plant tissues. The results of this study showed that the removal efficiencies of OM were above 50%. Regarding the effect of salinity on the removal of contaminants, the COD and BOD5 removals decreased 18% and 31%, respectively, from CW-C to CW-10 (p < .05). The sodium (Na+) concentration in Cyperus papyrus increased 82% when the salinity increased from 1 (CW-C) to 10 mS/cm (CW-10). In contrast, the chlorophyll concentration decreased 17% with increasing salinity (from 1 to 10 mS/cm). Finally, the vegetation presented mechanisms of salt tolerance, mainly Na+ accumulation in plant tissues. Despite these results, the technology of CWs could be a feasible alternative for the treatment of saline wastewater improving the plant selection.

Seasonal potential of Phragmites australis in nutrient removal to eliminate the eutrophication in Lake Burullus, Egypt

The present study was conducted to investigate the potential of the emergent macrophytes Phragmites australis to remediate nutrients and restore an eutrophic wetland (Lake Burullus, Egypt). The plant was sampled monthly for one year from 6 sites distributed equally along the northern and southern parts of this lake. Monthly significant variation in all investigated sediment and water nutrients for the northern and southern sites was recorded. The biomass of P. australis in the southern sites was greater than that of the northern sites; in addition, the above-ground biomass was greater than the below-ground biomass. The above-ground biomass increased from February until it reached its maximum during August and then decreased again. Likewise, the highest nutrient concentrations in the different tissues were recorded at the beginning of the growing season during winter and early spring and then gradually decreased with increasing plant biomass. Moreover, the nutrient content (g/m2) increased from the early growing season (February) and reached its peak during April–August and then decreased. Based on our results, P. australis could be used for the extraction of nutrients to reduce the eutrophication in Lake Burullus, if the above-ground biomass is harvested at its maximum value in August, as was the case regarding the maximum content of most nutrients.

Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C4 grass Panicum virgatum

Abstract Plant responses to major environmental drivers like precipitation can influence important aspects of carbon (C) cycling like soil CO2 efflux ( ). These responses may be predicted by two independent classes of drivers: plant size—larger plants respire more and produce a larger quantity of labile C, and plant economics—plants possessing more acquisitive plant economics strategies (i.e. high metabolic rate and tissue nutrient content) produce higher‐quality tissue that respires rapidly and decomposes quickly. At two sites in central Texas, USA with similar climates and differing soil characteristics, we examined the response of eight Panicum virgatum genotypes to three annual precipitation levels defined by the driest, average and wettest years from each site's precipitation history. We evaluated the individual and joint influence of plant genotypes and precipitation on and traits related to plant economics and plant size. We then used confirmatory path analysis to evaluate whether effects of precipitation on were in part related to effects of precipitation on plant economics traits or size (‘mediated’ effects). These genotypes exhibited variation in plant economics traits and above‐ground net primary productivity (ANPP), an above‐ground measure of plant size. Increasing precipitation increased and ANPP more than plant economics traits. At both sites, ANPP was the best predictor of . Moreover, the sites differed in the ways that plant size and plant economics traits combined with precipitation to influence . At the Austin site, the positive effect of precipitation on was mediated primarily by ANPP, offset by a smaller effect of leaf nitrogen content; no direct precipitation effect was detected. At the Temple site, increasing precipitation had positive direct and ANPP‐mediated effects on . This suggests that greater water limitation at Austin may strengthen the links between plant size and . Synthesis. Estimates of C cycling can be improved by accounting for mediation of precipitation effects on by plant economics traits and plant size in resource‐limited environments.