Increased Shoot Mass Research Articles

Physical Properties and Crop Performance of Four Substrate Fibers in Greenhouse Petunia Production

As peat (P) demand increases throughout the horticultural industry, alternative fibers must be evaluated. Sugarcane bagasse (B), wood fiber (W), and coconut coir (C) have received interest as domestically available alternatives to P, with demonstrated success in producing greenhouse crops. However, there is limited research comparing these materials to peat. This research evaluated the substrate properties and productivity of Petunia Supertunia Mini Vista ‘Indigo’ in pine bark substrates amended with C, W, B, or P and fertigated weekly at 100, 200, or 300 parts per million (ppm) nitrogen (N) to account for possible N immobilization. The container capacity was lowest and air-filled porosity was highest in W and B substrates. Substrate pH increased in W and B substrates, and C substrates were fertigated at 100 ppm N. Increasing the N rate increased the growth index in all substrates, especially B and W substrates later in the production period. Higher fertilization increased shoot mass, chlorophyll content, and blooms across all substrates, demonstrating that fertilizer supplementation may offset possible N immobilization. While plant growth and quality parameters were greatest in the P blend, increasing N applications produced similar-quality plants using alternative substrates, demonstrating that modifying fertilizer management practices can make alternative fibers a viable horticultural substrate.

Field application of silicon alleviates drought stress and improves water use efficiency in wheat.

Detrimental impacts of drought on crop yield have tripled in the last 50 years with climate models predicting that the frequency of such droughts will intensify in the future. Silicon (Si) accumulation, especially in Poaceae crops such as wheat (Triticum aestivum L.), may alleviate the adverse impacts of drought. We have very limited information, however, about whether Si supplementation could alleviate the impacts of drought under field conditions and no studies have specifically manipulated rainfall. Using field-based rain exclusion shelters, we determined whether Si supplementation (equivalent to 39, 78 and 117kg ha-1) affected T. aestivum growth, elemental chemistry [Si, carbon (C) and nitrogen (N)], physiology (rates of photosynthesis, transpiration, stomatal conductance, and water use efficiency) and yield (grain production) under ambient and drought (50% of ambient) rainfall scenarios. Averaged across Si treatments, drought reduced shoot mass by 21% and grain production by 18%. Si supplementation increased shoot mass by up to 43% and 73% in ambient and drought water treatments, respectively, and restored grain production in droughted plants to levels comparable with plants supplied with ambient rainfall. Si supplementation increased leaf-level water use efficiency by 32-74%, depending on Si supplementation rates. Water supply and Si supplementation did not alter concentrations of C and N, but Si supplementation increased shoot C content by 39% and 83% under ambient and drought conditions, respectively. This equates to an increase from 6.4 to 8.9 tonnes C ha-1 and from 4.03 to 7.35 tonnes C ha-1 under ambient and drought conditions, respectively. We conclude that Si supplementation ameliorated the negative impacts of drought on T. aestivum growth and grain yield, potentially through its beneficial impacts on water use efficiency. Moreover, the beneficial impacts of Si on plant growth and C storage may render Si supplementation a useful tool for both drought mitigation and C sequestration.

Defoliation affects the root competitive balance for N between Poa annua plants grown in a split‐root box

Background Plants compete aboveground for light and belowground for patchily distributed nutrients. Defoliation causes an immediate loss of leaf area and photosynthetic capacity, leading to reduced root growth, with hypothesised implications for nutrient uptake and nitrogen use efficiency. Methods In Experiment 1, we grew single plants in split root boxes with N supplied equally or unequally, with half the plants subject to repeated defoliation to quantify the impact of each treatment. In Experiment 2, we grew pairs of Poa annua plants in three-chamber split root boxes, with N supplied either to the outer chambers (no competition) or to a shared centre chamber (competition), to quantify the influence of defoliation on root competition. Results In Experiment 1, defoliation caused a significant decrease in root mass but did not affect root distribution between chambers, while differential N supply led to an 11% increase in shoot mass. In Experiment 2, strong root competition was seen in undefoliated plants under competitive conditions. Where one plant was defoliated, the other exhibited increased shoot mass and N content in competitive, but not noncompetitive conditions. Conclusions Our data suggest that plant belowground competitive success following defoliation may be strongly influenced by the spatial distribution of soil resources.

Salicylic acid mitigates the effects of mild drought stress on radish (Raphanus sativus) growth.

Water deficit is the most critical factor limiting plant growth and production and salicylic acid (SA) has potential for stress mitigation in plants; therefore, we evaluated the effect of SA on radish (Raphanus sativus L.) growth and ecophysiology under water deficit. Plants were sprayed with SA (100μM) or water (control), and irrigated at 80% (W80), 60% (W60), 40% (W40), and 20% (W20) of field capacity. The SA treatments and drought stress started 7days after sowing and lasted until the end of the cycle (30days after sowing). The morphophysiological analyses showed that radish plants had impaired growth at the lower water supply levels, but the treatment with SA reversed these growth restraints under moderate stress, leading to increases in shoot mass at W40 and storage root mass at W60 and W40. SA treatment also reversed the reduction of storage root volume at W60. The tendency of water deficit to increase F O and reduce F V /F M suggests possible damage to the photosystem II of drought-stressed plants. The parameters of gas exchange and photosynthetic pigments showed maintained photosynthetic efficiency, but total photosynthesis decreased due the lower shoot dry mass. Overall, exogenously applied SA reversed the growth restraints at W60 and W40, which revealed that SA was effective in mitigating the effects of moderate water deficit on biomass accumulation and partitioning in radish plants.

Optimization of Growing Medium and Preservation Methods for Plant Beneficial Bacteria, and Formulating a Microbial Biopreparation for Raspberry Naturalization

The current study focuses on the optimization of bacterial growing medium composition, including the carbon and nitrogen source in different concentrations, the pH value of the medium and the temperature. Optimization was performed for four environmental bacterial isolates belonging to the genera Arthrobacter, Pseudomonas and Rhodococcus, which were previously obtained from wild raspberries. These bacteria proved to be potent antagonists against certain fungal and fungal-like plant pathogens. Furthermore, three preservation methods and three sample preparation techniques were evaluated. In addition, a prebiotic supplementary blend based on previous research was tested. The research included a pot experiment to estimate the influence of bacterial cultures on the growth of plant shoots and roots, on the soil enzymatic activity and the content of macronutrients, minerals and nitrogen in the soil depending on the naturalization strategy. The best carbon and nitrogen source were chosen. The addition of a supplementary blend resulted in the increased growth of two bacterial isolates. Bacterial inoculum applied to the roots and watering resulted in increased shoot mass in objects infected with plant pathogens, although in plants without the pathogen infection, bacterial inoculum resulted in the decreased mass of plants. Naturalization strategy should be matched to the pathogens present at plantations.

Copper uptake, physiological response, and phytoremediation potential of Brassica juncea under biochar application

Biochar can enhance the phytoremediation of copper-contaminated soils by improving soil quality and increasing plant growth. However, the impact of biochar varies with the biomass feedstock and soil condition. Our study investigated the effect of biochar from orange bagasse-OBB and coconut husk-CHB and two copper concentrations (0.17 mg kg−1-CLS soil; 100 mg kg−1- CTS soil) on plant growth, copper uptake, and physiological response of Brassica juncea. The low- and high-Cu soils were also tested without biochar. We evaluated plant biomass, plant Cu, N and P, chlorophyll content, and chlorophyll’s transient fluorescence. Plant growth was meager without biochar, indicating that the high Cu concentration was not the only limiting factor. Biochar (OBB and CHB) increased shoot mass by 300–574% and root mass by 50–2900%, and improved chlorophyll content and photosynthetic activity by 6–16%. Both biochars were efficient in the low-Cu soil as they increased plant biomass, shoot copper concentration, and translocation factor. In the high-Cu soil, both biochars increased plant biomass and copper uptake and reduced shoot copper concentration and translocation factor. The CHB and OBB removed 342% and 783% more Cu from the contaminated soil than the Control; therefore, the OBB was proven to be the best choice for phytoremediation. Novelty statement Our study showed that the orange bagasse biochar can be successfully applied for the phytoremediation of copper-contaminated soils using Brassica juncea. The orange bagasse biochar was effective regardless of the copper level in the soil, removing twice as much copper as the coconut biochar; therefore, it can speed up the process and reduce the time needed to clean up the site. Highlights Biochar significantly improved the plant’s physiological response Biochar increased plant growth and copper uptake in the contaminated soil Translocation factor was increased in the clean soil and reduced in the contaminated soil Biochar from orange bagasse is more effective than coconut husk for phytoremediation

Plasticity in response to plant-plant interactions and water availability.

The plastic responses of plants to abiotic and biotic environmental factors have generally been addressed separately; thus we have a poor understanding of how these factors interact. For example, little is known about the effects of plant-plant interactions on the plasticity of plants in response to water availability. Furthermore, few studies have compared the effects of intra- and interspecific interactions on plastic responses to abiotic factors. To explore the effects of intraspecific and interspecific plant-plant interactions on plant responses to water availability, we grew Leucanthemum vulgare and Potentilla recta with a conspecific or the other species, and grew pairs of each species as controls in pots with the roots, but not shoots, physically separated. We subjected these competitive arrangements to mesic and dry conditions, and then measured shoot mass, root mass, total mass and root : shoot ratio and calculated plasticity in these traits. The total biomass of both species was highly suppressed by both intra- and interspecific interactions in mesic soil conditions. However, in drier soil, intraspecific interactions for both species and the effect of P.recta on L.vulgare were facilitative. For plasticity in response to water supply, when adjusted for total biomass, drought increased shoot mass, and decreased root mass and root : shoot ratios for both species in intraspecific interactions. When grown alone, there were no plastic responses in any trait except total mass, for either species. Our results suggested that plants interacting with other plants often show improved tolerance for drought than those grown alone, perhaps because of neighbor-induced shifts in plasticity in biomass allocation. Facilitative effects might also be promoted by plasticity to drought in root : shoot ratios.

HORMONE BALANCE AND SHOOT GROWTH IN WHEAT(Triticum durum Desf.) PLANTS AS INFLUENCED BY SODIUM HUMATES OF THE GRANULATED ORGANIC FERTILIZER

Humic acids are formed in soil during decomposition of organic residues and are capable of increasing plant productivity. Plant growing widely utilizes application of the most soluble preparations on the base of sodium and potassium humates possessing hormone-like activity. Humic substances are capable of stimulating plant growth in very low concentrations that determines the necessity of targeting their uptake by plants. Such a possibility is provided by placing fertilizers in the direct vicinity of the seeds. The effect of incrustation of Nitrofosque granules with sodium humate (SH) on the crop yield of spring durum wheat has been shown previously. In the present experiments, the data on the changes in growth and hormone content of wheat plants (Bashkirskaya 27 cv.) treated with SH included into the granules of organic-mineral fertilizer (OMF) are reported for the first time. Granules of fertilizers without SH and those containing 1.25×10-2 %, 2.5×10-2 % and 5×10-2 % of humic preparation (of the granule mass) were placed at the distance of 2-3 cm from the 1-day seedlings planted into the soil. OMF was obtained from poultry waste (chicken manure) and dolomite and SH was extracted from brown coal. Plants that obtained neither humates nor OMF served as the control. Leaf length and transpiration (according to the decline in the mass of vessels with plants) were measured starting from the third day after sowing. Leaf samples for determination of hormones with enzyme-linked immunoassay were sampled on day 9 and leaf area and plant mass were measured on day 21 after sowing. OMF granules without SH stimulated leaf elongation resulting in their significantly longer length compared with the control (42, 156, 187 and 274 mm against 47, 167, 199 and 294 mm, p ≤ 0.05) detected in the first leaves 3, 6 and 8 days after sowing and 14 days after sowing in the second leaves. Meanwhile an increase in the OMF dosage did not increase their length significantly compared to the lower dose. Addition of humic substances to the OMF granules increased the promotive effect of the preparation on the leaf elongation most clearly manifested in the case of intermediate SH concentration (2,5×10-2 %), which significantly increased the leaf length during the time of registration (3, 6, 8, and 14 days after sowing) compared to the application of OMF without SH (6, 11, 13 mm increment of the first leaves and 9.4, 9, 22 mm of the second leaves, р ≤ 0.05). Unlike OFM without SH, which application did not change the shoot mass and leaf area, combination of OFM with intermediate SH concentration increased shoot mass (from 538 to 583 mg, р ≤ 0,05). Leaf area was significantly greater than in the control in the case of intermediate and maximal SH concentration (increments were 385 and 283 mm2, р ≤ 0.05). Thus, addition of SH to OFM increased the effectiveness of the OFM action of growth characteristics. Accumulation of nitrogen in the shoots of the wheat plants supplied only with OFM without SH did not differ from the control, while combination of OFM with SH resulted in accumulation of nitrogen at the level (by 8-15 %, p ≤ 0.05) higher than in the control. Application of OFM without SH did not influence the content of studied hormones (auxins, cytokinins and abscisic acid — ABA), while addition of SH to the granules of fertilizers resulted in significantly higher concentration of abscisic acid (ABA) and cytokinins in the shoots, the 1.6-2.8 ng · g-1 increment (1.5-1.8 times) and 3.8-4.9 ng · g-1 increment (1.5-1.7 times) (р ≤ 0.05). Concentration of indole acetic acid (IAA) with intermediate SH concentration was higher than in the control (40 against 15 ng · g-1, р ≤ 0.05). The results obtained by us allow attributing increased effectiveness of fertilizers in the case of their supply with humates to their effect on the hormonal content. Increased content of hormones with promotive type of action is likely to enable activation of plant growth, while accumulation of ABA limits water losses by transpiration. The results of these laboratory experiments indicate perspectives of application of OMF containing sodium humates according to technology developed by us. Furthermore, the obtained data are of importance for revealing fundamental mechanisms, by which the action of humic compounds is manifested, in particular at the level of hormonal balance in plants.

Biomass Allocation in Response to Nitrogen and Phosphorus Availability: Insight From Experimental Manipulations of Arabidopsis thaliana.

Allocation of biomass to different organs is a fundamental aspect of plant responses and adaptations to changing environmental conditions, but how it responds to nitrogen (N) and phosphorus (P) availability remains poorly addressed. Here we conducted greenhouse fertilization experiments using Arabidopsis thaliana, with five levels of N and P additions and eight repeat experiments, to ascertain the effects of N and P availability on biomass allocation patterns. N addition increased leaf and stem allocation, but decreased root and fruit allocation. P addition increased stem and fruit allocation, but decreased root and leaf allocation. Pooled data of the five levels of N addition relative to P addition resulted in lower scaling exponents of stem mass against leaf mass (0.983 vs. 1.226; p = 0.000), fruit mass against vegetative mass (0.875 vs. 1.028; p = 0.000), and shoot mass against root mass (1.069 vs. 1.324; p = 0.001). This suggested that N addition relative to P addition induced slower increase in stem mass with increasing leaf mass, slower increase in reproductive mass with increasing vegetative mass, and slower increase in shoot mass with increasing root mass. Further, the levels of N or P addition did not significantly affect the allometric relationships of stem mass vs. leaf mass, and fruit mass vs. vegetative mass. In contrast, increasing levels of N addition increased the scaling exponent of shoot to root mass, whereas increasing levels of P addition exerted the opposite influence on the scaling exponent. This result suggests that increasing levels of N addition promote allocation to shoot mass, whereas the increasing levels of P addition promote allocation to root mass. Our findings highlight that biomass allocation of A. thaliana exhibits a contrasting response to N and P availability, which has profound implications for forecasting the biomass allocation strategies in plants to human-induced nutrient enrichment.

Substituting green or far-red radiation for blue radiation induces shade avoidance and promotes growth in lettuce and kale

Although red (R; 600–700 nm) and blue (B; 400–500 nm) radiation can be sufficient for plants grown indoors, other wavebands such as green (G; 500–600 nm) and far red (FR; 700–800 nm) can also regulate photosynthesis, plant morphology, and secondary metabolism. The objective of this study was to determine how substitutions of B radiation with G and/or FR radiation influence growth of leafy greens grown indoors under light-emitting diodes (LEDs). We postulated G and/or FR radiation (and low B radiation) would trigger shade-avoidance responses and thus promote biomass accumulation through increased radiation interception. We grew lettuce (Lactuca sativa ‘Rex’ and ‘Rouxai’) and kale (Brassica oleracea var. sabellica ‘Siberian’) under warm-white (WW) LEDs at 180 μmol·m–2·s–1 (400–800 nm) for 9–11 days and then transplanted seedlings into a hydroponic system with ten different lighting treatments. The air temperature (20 °C), photoperiod (20 h), total photon flux density (180 μmol·m–2·s–1; 400–800 nm), and fertility were maintained the same across treatments. In addition to WW and equalized-white (EQW) controls, combinations of B (peak =449 nm), G (peak =526 nm), and FR (peak =733 nm) LEDs, each at 0, 20, 40, or 60 μmol·m–2·s–1, were delivered in a R background (peak =664 nm) of 120 μmol·m–2·s–1. One month after seed sow, we collected data on shoot mass, leaf morphology, and pigmentation. Substituting G or FR radiation for B radiation promoted leaf expansion and increased shoot mass but decreased chlorophyll concentrations in all crops. For example, lettuce ‘Rex’ grown under 60 μmol·m–2·s–1 of G +120 μmol·m–2·s–1 of R radiation was 38% greater in plant diameter and 54% greater in shoot dry mass compared to those under 60 μmol·m–2·s–1 of B +120 μmol·m–2·s–1 of R radiation. Substituting B radiation with G radiation at 60 μmol·m–2·s–1 also reduced red coloration of lettuce ‘Rouxai’. At the same photon flux density, FR radiation increased leaf expansion and decreased red foliage coloration more than G radiation. We conclude that substituting G and/or FR radiation for B radiation triggers shade-avoidance responses, accelerating plant growth while decreasing pigment concentrations.

Pulse drip irrigation and fertigation water depths in the water relations of coriander

ABSTRACT This study was installed to evaluate the effect of pulse drip irrigation under different water depth levels (fertigation) in the main water relations of coriander crop (Coriandrum sativum). The experiment was installed under protected environment conditions, at UFRPE, Recife, Brazil. The experimental design was randomized blocks in a 2x5 factorial scheme, with three replications. Treatments consisted of two application types (continuous and pulsed irrigation), and five water depths with replacement of 40, 60, 80, 100 and 120% of crop evapotranspiration (ETc). Water demand was estimated through water balance using a drainage lysimetry. Six irrigation pulses were defined with a 60-minute-rest interval between two successive applications. Plants irrigated by pulses showed higher water productivity values (fresh and dry mass), higher water content (shoot and root), higher shoot mass production index and lower root mass production index and root-shoot ratio. The reduction of applied fertigation water depths increased plant water stress index. The irrigation pulses used ensured water content able to maintain the crop’s marketable quality. Pulse application in irrigation system increased shoot mass production index and reduced root mass production index.

Rain Garden Sedges Tolerate Cyclical Flooding and Drought

Although sedges (Carex L. spp.) are commonly recommended for planting in rain gardens, little work has been carried out in evaluating the ability of sedge species to tolerate the challenging moisture fluctuations in this environment. Seven sedge species native to the north central United States, yellow fox sedge [Carex annectens (E.P. Bicknell) E.P. Bicknell], plains oval sedge [Carex brevior (Dewey) Mack. ex Lunell], gray’s sedge (Carex grayi J. Carey), porcupine sedge (Carex hystericina Muhl. ex Willd.), palm sedge (Carex muskingumensis Schwein.), pennsylvania sedge (Carex pensylvanica Lam.), and sprengel’s sedge (Carex sprengelii Dewey ex Spreng.), were evaluated in a greenhouse trial to determine their ability to tolerate repeated flooding and drought cycles. Treatments consisted of two flood periods (2 or 7 days), followed by one of three drought set points measured by volumetric water content (VWC) thresholds of 0.05 (severe drought), 0.10 (moderate drought), or 0.15 m3·m−3 (drought onset). Each plant was subjected to a minimum of four flooding and drought cycles. For sprengel’s sedge, plains oval sedge, gray’s sedge, and yellow fox sedge, there was no significant difference in shoot counts between severe drought, moderate drought, and drought onset treatments. Shoot mass and root mass for all sedge species were significantly reduced under the severe drought set point. Plants subjected to the 7-day flood treatment exhibited significantly increased shoot mass compared with those in the 2-day flood treatment. Plains oval sedge showed a significantly higher shoot mass than all other species under all treatments. Visible damage ratings suggest that sprengel’s sedge, plains oval sedge, gray’s sedge, and yellow fox sedge could be suitable for the rain garden environment under all but the most extreme drought conditions. Results show that plains oval sedge, yellow fox sedge, and gray’s sedge may be able to tolerate harsh flooding and drought cycles that can occur in rain gardens. For the remaining species, supplemental irrigation of rain gardens should be considered during drought.

Timing of Nitrogen Fertilisation and the Effect of Poultry Manure on the Performance of Grapevines on Sandy Soil. I. Soil Analysis, Grape Yield and Vegetative Growth

A field trial with two Vitis vinifera L. cultivars, viz. Bukettraube (white) and Heroldrebe (red), grafted onto Ramsey, was carried out over a nine-year period on a sandy, duplex soil. The control (No) received no N, while three other treatments each received 50 kg N/ha in inorganic form. The N was applied either as three equal installments, split between budbreak, fruitset and post-harvest (N1), or as a single application at budbreak (N2), or as a single postharvest application (N3). A fifth treatment (N4) received 50 kg N/ha at budbreak in the form of poultry manure. A winter cover crop (rye) was sown after harvest, chemically controlled before budbreak with a herbicide and left as an organic mulch on the soil surface. This cover crop management system maintained the soil's organic material (SOM) at the original level for all inorganic treatments, while N4 increased SOM. On average, Bukettraube yielded 11.4 t/ha, in comparison to only 6.0 t/ha for Heroldrebe. Yields of the four fertilised treatments (Ni, N2, N3 and N4) were comparable for each individual cultivar. Relative to N0, fertilisation increased yields by 24% and 48% for Bukettraube and Heroldrebe, respectively. In comparison to the control, all four fertilisation treatments increased shoot mass, with Nz being significantly higher than Ni, NJ and N4. The fact that Nz stimulated shoot growth, without a concomitant increase in yield, indicated that a single application of N at bud break can cause excessive growth, even on low-potential soil. In the case of Bukettraube, grapes from the Nz treatment showed the highest incidence of bunch rot during some seasons. Under the cultivation practices followed in this trial, split applications of N (budbreak, fruitset, post-harvest) or a single application during the post-harvest period was compatible with the most desirable pattern of vine growth and fruit development. Application of poultry manure was not associated with any specific advantages or disadvantages. Soil analysis showed that the control vines were fairly well supplied with mineral N at budbreak, but under-supplied at the time of fruitset.

Different Root and Shoot Responses to Mowing and Fertility in Native and Invaded Grassland

Grassland root responses to mowing and fertility are less well known than shoot responses, even though as much as 90% of productivity in semiarid grasslands occurs belowground. Thus, understanding root responses may aid the management of invasive grassland species such as Agropyron cristatum (L.) Gaerth (crested wheatgrass). We asked whether root responses reflect shoot responses to mowing and fertility in native grassland with and without a major component of crested wheatgrass. We subjected grasslands in northern Montana to 5 yr of mowing at two nitrogen (N) levels and followed root responses with minirhizotrons. Surprisingly, the roots of both native and invaded grasslands were unaffected by mowing and N addition, despite significant changes in shoot mass across both vegetation types. Root length was significantly greater beneath areas heavily occupied by crested wheatgrass (363 m · m-2 image ± 200, mean ± standard deviation [SD]) than areas comprising largely native grassland (168 m · m-2 image ± 128 SD). Also, no interactions occurred between year and any other factor, indicating that there were no changes in belowground responses over the 5 yr examined. In contrast, shoot mass was significantly reduced by mowing (not mowed, 612 g · m-2 ± 235 SD; mowed, 239 g · m-2 ± 81 SD) and was significantly increased by N addition (no added N, 380 g · m-2 ± 215 SD; added N, 488 g · m-2 ± 287 SD). In conclusion, 5 yr of mowing decreased shoot mass, but not root mass. On the other hand, 5 yr of N addition increased shoot mass, but not root mass. Given that most production and competition in grasslands occurs belowground, this suggests that mowing may not be a successful tool for reducing crested wheatgrass root length, regardless of soil fertility.

THE POTENTIAL USE OF ANAEROBIC BAFFLED REACTOR (ABR) EFFLUENT FOR PERI-URBAN HORTICULTURE

Currently under investigation by the eThekwini Water and Sanitation is the use of anaerobic baffled reactors (ABR) by local communities to treat wastewater. Studies undertaken at the University of KwaZulu-Natal, South Africa show that ABR effluent has the potential to improve soil nutrient status without adversely affecting soil properties. However, the availability of these nutrients for plant uptake up these nutrients has not been investigated and the effect on crop growth and yield is not known. This study aimed to (i) compare the use of ABR effluent as a fertilizer source and standard inorganic fertilizer recommendations for bean (Phaseolus vulgaris) and Swiss chard (Beta vulgaris) growth and; and (ii) determine the effect of high nutrient concentrations in ABR effluent on bean seed germination and seedling growth. Pot experiments were laid out for each crop species as a 3×3×2 factorial treatment structure using a completely randomized design with the following factors: soil type (3 levels - Inanda, soil from Newlands Mashu (Sepane soil form) and Cartref); Fertilizer application (3 levels - no fertilizer, recommended rate and half the recommended rate); Water (2 levels - ABR effluent and tap water, applied as ‘bucket’ irrigation). Obtained data indicated that Swiss chard plants grown at recommended fertilizer rates using tap water in irrigation did not differ significantly (P>0.05) with respect to dry matter accumulation and leaf area from those irrigated with ABR effluent at recommended and half rates in all three soil types. Bean seeds germinated using ABR effluent showed radicle protrusion earlier than those under tap water; radicles were longer and produced more root mass compared to those germinated using tap water. These findings suggest that the type of crop species and its nutrient requirements, stage of growth and development and the timing of application and soil properties would be important factors to consider when using ABR effluent. High P concentration (mg/L) in the ABR effluent may be associated with increased shoot mass and extensive root growth.

Phosphorus nutrition‐mediated effects of arbuscular mycorrhiza on leaf morphology and carbon allocation in perennial ryegrass

The aim of this work was to disentangle phosphorus status-dependent and -independent effects of arbuscular mycorrhizal fungus (AMF) on leaf morphology and carbon allocation in perennial ryegrass (Lolium perenne). To this end, we assessed the P-response function of morphological components in mycorrhizal and nonmycorrhizal plants of similar size. AMF (Glomus hoi) stimulated relative P-uptake rate, decreased leaf mass per area (LMA), and increased shoot mass ratio at low P supply. Lower LMA was caused by both decreased tissue density and thickness. Variation in tissue density was almost entirely caused by variations in soluble C, while that in thickness involved structural changes. All effects of AMF were indistinguishable from those mediated by increases in relative P-uptake rate through higher P-supply rates. Thus the relationships between relative P-uptake rate, leaf morphology and C allocation were identical in mycorrhizal and nonmycorrhizal plants. No evidence was found for AMF effects not mediated by changes in plant P status.

Interactive Influences of Fertility and Nodulation on Growth, Nutrition, and Water Relations of European Alder in a Mine Soil

Abstract Actinorhizal nodulation of European alder (Alnus glutinosa[L.] Gaertn.) as influenced by substrate fertility was assessed for its effects on seedling growth and physiology. After a brief period in seed flats, seedlings were transplanted to a mine soil where they resided for 18 months, and three fertility regimes were imposed by application of differing nutrient solution concentrations while two distinct levels of nodulation were created through methyl bromide fumigation. Ultimately, seedlings in nonfumigated soil had > 5Xthe nodules of those grown in fumigated soil, and rising fertility stimulated nodule formation in the former. Heavy nodulation resulted in a 35% increase in shoot mass and a 60% increase in root mass on average, responses that exceeded those to fertilization for the latter. Seedlings with abundant nodules had higher foliar concentrations of total N, NO3, K, and Cu and lower concentrations of Ca, Mg, S, Fe, Mn, Zn, Mo, and Al overall, than were found in those with minimal nodulation. In turn, soil in which heavily nodulated seedlings were grown had higher total N, NO3, Ca, Mg, S, Fe, Mn, Zn, and Al concentrations but a lower Mo concentration than fumigated soil. Fertility regime effects on nutrition were readily apparent, although considerably more so in the mine soil than in foliage. During a simulated drought episode, predawn and midday xylem pressure potentials within the high fertility treatment were lower in heavily nodulated seedlings than in those with few nodules, and the water potentials in soil in which the heavily nodulated seedlings resided were lower overall as well. Collectively, these results provide insight into approaches to most effectively exploit the benefits European alder offers as a reforestation species for difficult sites.

Interactive Influences of Fertility and Nodulation on Growth, Nutrition, and Water Relations of European Alder in a Mine Soil

Actinorhizal nodulation of European alder (Alnus glutinosa[L.] Gaertn.) as influenced by substrate fertility was assessed for its effects on seedling growth and physiology. After a brief period in seed flats, seedlings were transplanted to a mine soil where they resided for 18 months, and three fertility regimes were imposed by application of differing nutrient solution concentrations while two distinct levels of nodulation were created through methyl bromide fumigation. Ultimately, seedlings in nonfumigated soil had > 5Xthe nodules of those grown in fumigated soil, and rising fertility stimulated nodule formation in the former. Heavy nodulation resulted in a 35% increase in shoot mass and a 60% increase in root mass on average, responses that exceeded those to fertilization for the latter. Seedlings with abundant nodules had higher foliar concentrations of total N, NO3, K, and Cu and lower concentrations of Ca, Mg, S, Fe, Mn, Zn, Mo, and Al overall, than were found in those with minimal nodulation. In turn, soil in which heavily nodulated seedlings were grown had higher total N, NO3, Ca, Mg, S, Fe, Mn, Zn, and Al concentrations but a lower Mo concentration than fumigated soil. Fertility regime effects on nutrition were readily apparent, although considerably more so in the mine soil than in foliage. During a simulated drought episode, predawn and midday xylem pressure potentials within the high fertility treatment were lower in heavily nodulated seedlings than in those with few nodules, and the water potentials in soil in which the heavily nodulated seedlings resided were lower overall as well. Collectively, these results provide insight into approaches to most effectively exploit the benefits European alder offers as a reforestation species for difficult sites.

Ornamental Cabbage Quality Improved by Continual Fertilization through Center-head Coloration

Current fertilizer recommendations for ornamental cabbage (Brassica oleracea var. acephala DC.) suggest applying 150 to 300 mg·L-1 N until the initiation of color development, after which fertilization should be reduced or discontinued. Because these plants are actively growing during cool weather when coloration is initiated, nutrient deficiencies may reduce overall plant quality. The objectives of this study were to investigate N to K ratios for plant growth of ornamental cabbage and the effects of continual and discontinued fertilization during the period of coloration. Fertilizing with 150 to 200 mg·L-1 N and 150 to 200 mg·L-1 K produced high-quality plants and provided sufficient tissue concentrations of N and K. Center-head coloration was not inhibited by N concentrations as high as 250 mg·L-1. Ceasing fertilization prior to center-head coloration resulted in the rapid depletion of N, P, and K concentrations in the lower foliage, leading to the appearance of deficiency symptoms and lower leaf loss. Plants were still actively growing as measured by increased shoot mass during the early stages of coloration; therefore, growers should continue to provide a complete analysis fertilizer at N concentrations ≥150 mg·L-1 until market date.

Seed size and adventitious (nodal) roots as factors influencing the tolerance of wheat to waterlogging

In a glasshouse study, two experiments were conducted to understand how inherent variability, such as the seed size or mass, and formation of adventitious nodal roots might influence the tolerance of various wheat and triticale cultivars at different growth stages to waterlogging. Waterlogging at germination resulted in 11% seedling mortality, but the waterlogged seedlings had a 19% increase in shoot mass per plant, with no difference in root mass compared with non-waterlogged seedlings. Waterlogging at the 3-leaf stage was deleterious to only a few cultivars. On average, larger seed resulted in greater plant growth for most of the cultivars, and seed mass was positively related to the plant biomass and adventitious nodal root mass under waterlogged conditions. A decreasing oxygen concentration with increasing duration of waterlogging and soil depth did not affect the plant growth and visual stress symptoms, chlorosis, until the oxygen concentration decreased to less than 10% in the bottom depths. The highest yielding triticale cultivar, Muir, and wheat cultivars Brookton and Frame had the greatest seed mass, plant biomass, and relative growth rates under waterlogged conditions, compared with the lowest yielding wheat cultivars, Amery, Silverstar, and More. However, the degree of 'waterlogging tolerance', expressed as the percent ratio of plant biomass or growth rates under waterlogged conditions relative to the non-waterlogged control conditions, appeared to be greatest for the low-yielding cultivars, indicating a 'cautious approach' when screening tolerant cultivars.