Pot-grown Plants Research Articles

A water-centred framework to assess the effects of salinity on the growth and yield of wheat and barley

We used a water-centred framework (yield = transpiration × transpiration efficiency × harvest index) to investigate the effect of soil salinity on growth and yield of wheat and barley. Our working hypothesis is that salinity reduces transpiration proportionally more than transpiration efficiency. We established a glasshouse experiment with the factorial combination of four varieties (wheat: Janz, Krichauff; barley: Mundah, Keel) and three soil treatments: a control with no NaCl added, and NaCl added to achieve soil EC1:5 0.75 dS m−1 and 1.5 dS m−1. Pot-grown plants were watered to weight to determine transpiration and shoot dry matter was determined using a non-destructive image analysis system. Consistent with our hypothesis, salinity reduced transpiration (30–60%) proportionally more than transpiration efficiency (0–35%); transpiration accounted for 90% of the variation in shoot growth across varieties and treatments. Against this pattern, there were time- and variety-dependent responses. The rate of leaf appearance and the transpiration efficiency of Janz, Krichauff and Keel showed a two-stage response to salinity. In stage 1, salt-stressed plants maintained rate of leaf appearance and transpiration efficiency close to or slightly below those of the controls. After a clear break point where the slope changed, stage 2 was characterised by a substantial reduction in both traits. Stage 2 was not evident in salt-stressed Mundah, which maintained a relatively high rate of leaf appearance and transpiration efficiency. Across species, harvest index increased from 0.40 in controls to 0.47 at 0.75 dS m−1. Harvest index of plants grown at 1.5 dS m−1 was unaffected in wheat, and was reduced in barley. We propose that an understanding of the effect of salinity on crop development, growth and yield requires integration of low-level traits in a framework of resource capture, resource-use efficiency and plant allocation. Osmotic stress tolerance, Na+ exclusion, and tissue tolerance to accumulated Na+ would improve yield of salt-stressed crops to the extent that these traits contribute to the maintenance of water uptake and harvest index.

First Korean Report of Powdery Mildew on Tropaeolum majus

Garden nasturtium (Tropaeolum majus L.) is a herbaceous plant with beautiful red flowers, native to South America. In Korea it is widely planted as an ornamental in pots and flower beds. In October 2008, several plants showing typical symptoms of powdery mildew were found in Yongin, Korea. The disease usually started as chlorotic leaf lesions without definite margins, which later developed into necrotic angular leaf spots with definite margins (Fig. 1). Even with weak infections, the plants often detract from the beauty of glossy leaves. The whitish fungal structures appeared on the abaxial leaf surface (Fig. 2A). Mild infection on the flower, causing chlorotic discoloration, was also noticed. A voucher specimen was deposited in Korea University herbarium (KUS-F23743). Observations on the light microscope (Zeiss AX10 and Olympus BX51) revealed that mycelium is predominantly endophytic with the presence of conidiophores emerging through stomatal openings (Fig. 2B). The conidiophores were hyaline, cylindrical, 160-320× 4.5-6 μm, simple or occasionally branched one or two times at random positions, producing conidia singly, followed by 2-3 straight cells (Fig. 2B). Conidia were dimorphic, with primary conidia navicular, 60-82×15-25 μm, and secondary conidia oblongelliptical to cylindric, 54-90×14-20 μm; both hyaline, occasionally seen as pale brownish or greenish due to dense cytoplasm, lacking distinct fibrosin bodies, with angular/reticulated wrinkling of outer wall (Fig. 2CD Farr and Rossman, 2009). To our knowledge, however, this is the first record as a pathogen of T. majus in Korea. Occurrence of powdery mildew on T. majus, as far as we observed, was restricted to the pot-grown plants which were placed in poor lighting condition in Yongin. No infections were found in the plants growing in outdoor flower beds, in spite of careful observations in several localities including Yangpyeong. Therefore it is highly recommended to avoid powdery mildew infections that garden nasturtium should be grown in sunny, well-ventilated nursery. Nevertheless, powdery mildew infection on garden nasturtium is a potential threat for safe production of seedlings in nursery business.

Spine micromorphology of normal and hyperhydric Mammillaria gracilis Pfeiff. (Cactaceae) shoots

Artificial conditions of tissue culture affect growth and physiology of crassulacean acid metabolism plants which often results in formation of hyperhydric shoots. In in vitro conditions Mammillaria gracilis Pfeiff. (Cactaceae) growth switches from organized to unorganized way, producing a habituated organogenic callus which simultaneously regenerates morphologically normal as well as altered hyperhydric shoots. In this study, influence of tissue culture conditions on morphology of cactus spines of normal and hyperhydric shoots was investigated. Spines of pot-grown Mammillaria plants and of in vitro regenerated shoots were examined with stereo microscope and scanning electron microscope. The pot-grown plants had 16-17 spines per areole. In vitro grown normal shoots, even though they kept typical shoot morphology, had lower number of spines (11-12) and altered spine morphology. This difference was even more pronounced in spine number (six to seven) and morphology of the hyperhydric shoots. Scanning electron microscopy analysis revealed remarkable differences in micromorphology of spine surface between pot-grown and in vitro grown shoots. Spines of in vitro grown normal shoots showed numerous long trichomes, which were more elongated on spines of the hyperhydric shoots; the corresponding structures on spine surface of pot-grown plants were noticed only as small protrusions. Scanning electron microscopy morphometric studies showed that the spines of pot-grown plants were significantly longer compared to the spines of shoots grown in tissue culture. Moreover, transverse section shape varies from elliptical in pot-grown plants to circular in normal and hyperhydric shoots grown in vitro. Cluster and correspondence analyses performed on the scanning electron microscope obtained results suggest great variability among spines of pot-grown plants. Spines of in vitro grown normal and hyperhydric shoots showed low level of morphological variation among themselves despite the significant difference in shoot morphology.

First Report of Leaf Spot Caused by Pseudomonas cichorii on Coreopsis lanceolata in Italy.

Coreopsis lanceolata L. (Compositae), an ornamental species grown in parks and gardens, is very much appreciated for its long-lasting flowering period. In August of 2008, pot-grown plants with necrotic leaf lesions were observed in a commercial nursery located near Biella (northern Italy). Lesions were present, especially along the margin of basal leaves, and sometimes had a chlorotic halo. On infected leaves, dark brown necrosis developed. Leaf stalks were sometimes affected. In many cases, the leaves, especially those at collar level, were withered. Of 1,500 plants, 15% were infected by the disease. Microscopic examination did not reveal any fungal structures within the lesions. Small fragments of tissue from 30 affected leaves were macerated for 15 min in casein hydrolysate and 0.1-ml aliquots of the resulting suspension were spread onto Luria Bertani agar (LB) and potato dextrose agar (PDA). Plates were maintained at 22 ± 1°C for 48 h. No fungi were isolated from the leaf spots on LB or PDA. Colonies similar to those of Pseudomonas spp. were consistently isolated on LB. Colonies were fluorescent on King's medium B, levan negative, oxidase positive, potato soft rot negative, arginine dihydrolase negative, and tobacco hypersensitivity positive (LOPAT test). The bacterial colonies were identified as Pseudomonas cichorii (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers 27F and 1492R and sequenced (GenBank Accession No. FJ534557). BLAST analysis (1) of the 998-bp segment showed a 98% homology with the sequence of P. cichorii. The pathogenicity of one isolate was tested twice by growing the bacterium in nutrient broth shake cultures for 48 h at 20 ± 1°C. The suspension was centrifuged, the cell pellet resuspended in sterile water to a concentration of 107 CFU/ml, and 30 4-month-old healthy coreopsis plants were sprayed with the inoculum. The same number of plants was sprayed with sterile nutrient broth as a control. After inoculation, plants were covered with plastic bags for 48 h and placed in a growth chamber at 20 ± 1°C. Five days after inoculation, lesions similar to those seen in the field were observed on all plants inoculated with the bacterium, but not on the controls. Ten days later, 40% of the leaves were withered. Isolations were made from the lesion margins on LB and the resulting bacterial colonies were again identified as P. cichorii. The pathogen caused the same symptoms also on plants of Dendranthema frutescens (cv. Camilla), Chrysanthemum morifolium (cvs. Eleonora and Captiva), and an Osteospermum sp. (cv. Wild side) when artificially inoculated with the pathogen with the same methodology. The same bacterial leaf spot caused by P. cichorii was observed in 2005 in other nurseries in the same area on Phlox paniculata (3). To our knowledge, this is the first report of bacterial leaf spot caused by P. cichorii on C. lanceolata in Italy.

Water Relations and Abscisic Acid in Pot-grown Strawberry Plants under Limited Irrigation

We investigated the effect of full irrigation (FI), deficit irrigation (DI), partial root zone drying (PRD), and nonirrigation (NI) on soil and plant–water relations, leaf stomatal conductance (gs), and abscisic acid (ABA) concentration in the xylem sap ([ABA]xylem) of pot-grown strawberry plants (Fragaria ×ananassa cv. Honeoye) in a greenhouse experiment. The DI and PRD treatments, irrigated with 70% of the volume of FI, reduced soil water content (θ), whereas crown water potential (ψcrown), leaf water potential (ψleaf), and gs were only significantly reduced from 11 to 15 days after initiation of irrigation treatments. Although [ABA]xylem was not significantly affected by the DI and PRD treatments, the NI plants increased [ABA]xylem, which coincided with decreased ψcrown, ψleaf, and gs 3 to 4 days after withholding irrigation. When ψcrown dropped below a critical value of −0.4 MPa, [ABA]xylem was linearly correlated with ψcrown. The gs tended to decrease as a function of [ABA]xylem, but gs was also affected by the water vapor pressure deficit (VPD) of the air. It is concluded that we did not observe a significant difference between strawberry plants grown in PRD and DI because ψcrown had to be below −0.4 MPa and soil water potential (ψsoil) had to be below −0.25 MPa before [ABA]xylem increased, these values were only reached toward the end of the experimental period (11–15 days after initiation of irrigation treatments).

EFFECT OF HIGH TEMPERATURE ON FRUIT QUALITY OF POT-GROWN STRAWBERRY PLANTS

We investigated the effect of high temperature on the fruit quality of pot-grown strawberry plants with a limited number of fruit in greenhouse and growth chamber experiments. In the greenhouse, plants were grown under either normal greenhouse (control) temperatures or in a small plastic tunnel, which held the air temperature a few degrees higher than the control. In the growth chamber, the air temperature was set to either 35/20°C (day/night) or 25/20°C. The fruits weight content showed no relation to temperature regime. Ascorbic acid content was not influenced by high temperature in either experiment. However, the anthocyanin content was decreased at high temperature in the growth chamber. Because the periods from anthesis to harvesting were almost the same in both temperature regimes, high temperature might reduce the internal content of anthocyanins in marketed fruits.

In vitro plantlet regeneration of “dwarf” Indian olive (Elaeocarpus robustus Roxb.): a fruit plant of Bangladesh

A plantlet regeneration protocol was developed on pot-grown mature plants of Elaeocarpus robustus Roxb. cv. Dwarf from nodal and leaf explants. The best yield of adventitious shoots was achieved from the leaf-derived calli in a modified MS (MMS1, half strength of major salts, full strength of minor salts, and vitamins) medium containing 4.0 μM BA + 4.0 μM Kn + 0.5 μM NAA + 15% coconut water (CW). The shoot multiplication rate was amplified about twofold per culture after the addition of 15% CW to the medium. The rate of shoot multiplication reached maximum at the 5th subculture, and it maintained this rate throughout the 3 subsequent subcultures. The best rooting in vitro was investigated by subculturing the microcuttings in an MMS2 (half strength of both major salts and minor salts and full strength of vitamins) medium containing 1.0 μM IBA in the dark for one initial week at 30°C, followed by subculturing them in a plant-growth regulator (PGR)-free medium in the light. The plantlets raised in vitro were successfully established under ex vitro conditions.

Effects of Pot Size on Leaf Production and Essential Oil Content and Composition of Eucalyptus citriodora hook. (Lemon-Scented Gum)

The influence of pot size on plant height, stem diameter, dry leaf biomass, essential oil content, and composition of Eucalyptus citriodora was investigated in this experiment. Both the physical and the chemical properties of pot-grown plants were significantly affected by pot size. Plants grown in larger pots were generally taller, had thicker stems and wider canopies, grew more branches, and produced more leaves that were larger than plants grown in smaller pots. The highest essential oil concentrations (∼ 1.2%) were observed in plants grown in 1-liter (20-cm diameter) and 5-liter (11 cm diameter) pots. Essential oil composition was fairly similar for all pot sizes. We conclude that Eucalyptus citriodora can be grown in pots, preferably in 10- or 5-liter pots, and thus provide fresh leaves on a daily basis.

Culture and Propagation of Laboratory Populations of the African Butterfly Bicyclus anynana

INTRODUCTIONThis protocol describes methods required for the culture of the African butterfly Bicyclus anynana. The larvae are typically fed and maintained on pot-grown maize plants (Zea mays) that are ~50 cm high. Males and females can be separated as pupae or adults. Adults are fed on moist banana and will readily mate in the laboratory. Females lay eggs on available grass plants. We use a standard temperature of 27°C (because an approximate rule is that developmental time is twice as long at 20°C), a high relative humidity of ~60%-70% (the exact level is not critical), and a 12:12 photoperiod similar to the climate experienced in the wet season near the equator. Both larval and pupal molts are gated by photoperiod and can be readily timed (e.g., by use of time-exposure filming). To set up cohorts of standard developmental stages, an appropriate timing for this photoperiod is chosen: Pupation usually occurs shortly after lights out, and larval molts also occur during the night. At ~27°C, egg development takes 4 d, and the total generation time is 5-6 wk, yielding about eight generations a year in selection experiments.

Root signals and stomatal closure in relation to photosynthesis, chlorophyll a fluorescence and adventitious rooting of flooded tomato plants

An investigation was carried out to determine whether stomatal closure in flooded tomato plants (Solanum lycopersicum) results from decreased leaf water potentials (psi(L)), decreased photosynthetic capacity and attendant increases in internal CO(2) (C(i)) or from losses of root function such as cytokinin and gibberellin export. Pot-grown plants were flooded when 1 month old. Leaf conductance was measured by diffusion porometry, the efficiency of photosystem II (PSII) was estimated by fluorimetry, and infrared gas analysis was used to determine C(i) and related parameters. Flooding starting in the morning closed the stomata and increased psi(L) after a short-lived depression of psi(L). The pattern of closure remained unchanged when psi(;L) depression was avoided by starting flooding at the end rather than at the start of the photoperiod. Raising external CO(2) concentrations by 100 micromol mol(-1) also closed stomata rapidly. Five chlorophyll fluorescence parameters [F(q)'/F(m)', F(q)'/F(v)', F(v)'/F(m)', non-photochemical quenching (NPQ) and F(v)/F(m)] were affected by flooding within 12-36 h and changes were linked to decreased C(i). Closing stomata by applying abscisic acid or increasing external CO(2) substantially reproduced the effects of flooding on chlorophyll fluorescence. The presence of well-aerated adventitious roots partially inhibited stomatal closure of flooded plants. Allowing adventitious roots to form on plants flooded for >3 d promoted some stomatal re-opening. This effect of adventitious roots was not reproduced by foliar applications of benzyl adenine and gibberellic acid. Stomata of flooded plants did not close in response to short-lived decreases in psi(L) or to increased C(i) resulting from impaired PSII photochemistry. Instead, stomatal closure depressed C(i) and this in turn largely explained subsequent changes in chlorophyll fluorescence parameters. Stomatal opening was promoted by the presence of well-aerated adventitious roots, implying that loss of function of root signalling contributes to closing of stomata during flooding. The possibility that this involves inhibition of cytokinin or gibberellin export was not well supported.

Effects of multiple applications of chemical elicitors onBotrytis cinereainfecting Geraldton waxflower

Geraldton waxflower is susceptible to postharvest floral abscission caused by Botrytis cinerea infection. Pot- and field-grown waxflower cv. Mullering Brook plants and/or their harvested sprigs were spray treated with three known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH) or silicon (Si), and challenged with Botrytis cinerea after harvest. The efficacy of multiple MeJA, MeJA combined with BTH or Si and combined preand postharvest MeJA treatments in suppressing B. cinerea disease and floral abscission was assessed. Preharvest foliar applications of MeJA (1000 μM; two or four times), MeJA combined with BTH (150 mg/L) and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress B. cinerea development and floral abscission from harvested sprigs. MeJA plus Si applied to pot-grown plants slightly and significantly (P<0.05) increased disease incidence and severity and flower fall. However, application of a MeJA postharvest (1000 μM) spray or pre- (1000 μM) plus postharvest (500 μM) MeJA sprays, significantly (P<0.05) reduced B. cinerea incidence and severity on sprigs from field-grown plants. Overall, the preharvest plus postharvest 1000 μMMeJA spray treatment consistently and significantly (P<0.05) suppressed B. cinerea infection on flowers from both pot- and field-grown plants. However, there was little or no impact of these treatments on floral abscission. Thus, multiple applications of chemical elicitors do not show promise as an approach to controlling B. cinerea-induced postharvest floral abscission in Geraldton waxflower.

EFFECTS OF COMBINED METHYL JASMONATE AND ETHYLENE-INHIBITOR TREATMENTS AGAINST BOTRYTIS CINEREA INFECTING GERALDTON WAXFLOWER

Infections by Botrytis cinerea cause ethylene-mediated flower fall in cut Geraldton waxflower (Chamelaucium uncinatum). Methyl jasmonate (MJ) is a known host plant defence elicitor, and MJ treatments have demonstrated potential to suppress Botrytis on waxflower. However, MJ can also induce waxflower flower abscission. Flower fall in waxflower can be prevented by treatments with anti-ethylene agents. Pot and field experiments were conducted to determine if combining MJ and anti-ethylene treatments could suppress Botrytis and prevent flower fall. Waxflower 'My Sweet Sixteen' plants were spray-treated pre- and postharvest with MJ (1000 mu M), treated postharvest with either 1-methylcyclopropene (MCP fumigation; 0.08 mu l L-1) or silver thiosulphate (STS pulse; 0.5 mM), and then challenged with Botrytis. Pre- and postharvest MJ treatments reduced Botrytis development, but increased flower fall. In combination with MJ treatment, MCP treatment did not reduce either Botrytis disease or flower fall. MJ in combination with STS reduced (P < 0.05) disease severity for up to 6 days on sprigs harvested from pot-grown plants. However, this combination tended to increase Botrytis disease severity on sprigs from field-grown plants 6 days after inoculation. This inconsistency between pot- and field-grown plants suggests an overriding influence of environment and/or plant management on inducible host defence.

Influence of Weather Conditions on Infection of Peach Fruit byTaphrina deformans

ABSTRACT The effect of environment on the infection of peach fruit by Taphrina deformans was investigated using orchard observations under natural conditions (in 2001 to 2004) or in trees managed in such a way to exclude rainfall. These conditions were then validated using pot-grown peach plants exposed to single infection events and independent orchard observations. Leaf curl incidence was related to rainfall, length of wet periods, and the temperature during wetness and during the incubation period, as well as to the developmental stage of flowers and fruit. Weather conditions before petal fall did not influence fruit infection. After petal fall, rainfall and the duration of the wet period triggered by rainfall played a key role in infection occurrence. The minimum rainfall required for infection was 12 mm, with at least 24 h of wetness interrupted by no more than 4 h. No infection occurred when temperature was >/=17 degrees C during the wet period or >19 degrees C during incubation. Disease symptoms appeared on fruit after approximately 3 weeks of incubation, which is equivalent to 240- to 290-degree-days (base 0 degrees C). The period for fruit infection was relatively short being from petal fall until air temperature remained greater than 16 degrees C. During this period, the incidence of fruit that developed symptoms was closely related to the number of favorable events and the total wetness duration during such events.

Evaluation of physiological traits for improving drought tolerance in faba bean (Vicia faba L.)

Among grain legumes, faba bean is becoming increasingly popular in European agriculture due to recent economic and environmental interests. Faba bean can be a highly productive crop, but it is sensitive to drought stress and yields can vary considerably from season to season. Understanding the physiological basis of drought tolerance would indicate traits that can be used as indirect selection criteria for the development of cultivars adapted to drought conditions. To assess genotypic variation in physiological traits associated with drought tolerance in faba bean and to determine relationships among these attributes, two pot experiments were established in a growth chamber using genetic materials that had previously been screened for drought response in the field. Nine inbred lines of diverse genetic backgrounds were tested under adequate water supply and limited water conditions. The genotypes showed substantial variation in shoot dry matter, water use, stomatal conductance, leaf temperature, transpiration efficiency, carbon isotope discrimination (Δ13C), relative water content (RWC) and osmotic potential, determined at pre-flowering vegetative stage. Moisture deficits decreased water usage and consequently shoot dry matter production. RWC, osmotic potential, stomatal conductance and Δ13C were lower, whereas leaf temperature and transpiration efficiency were higher in stressed plants, probably due to restricted transpirational cooling induced by stomatal closure. Furthermore, differences in stomatal conductance, leaf temperature, Δ13C and transpiration efficiency characterized genotypes that were physiologically more adapted to water deficit conditions. Correlation analysis also showed relatively strong relationships among these variables under well watered conditions. The drought tolerant genotypes, ILB-938/2 and Melodie showed lower stomatal conductance associated with warmer leaves, whereas higher stomatal conductance and cooler leaves were observed in sensitive lines (332/2/91/015/1 and Aurora/1). The lower value of Δ13C coupled with higher transpiration efficiency in ILB-938/2, relative to sensitive lines (Aurora/1 and Condor/3), is indeed a desirable characteristic for water-limited environments. Finally, the results showed that stomatal conductance, leaf temperature and Δ13C are promising physiological indicators for drought tolerance in faba bean. These variables could be measured in pot-grown plants at adequate water supply and may serve as indirect selection criteria to pre-screen genotypes.

Roles of Auxin and Cytokinin in Soybean Pod Setting

Soybean plants differentiate abundant floral buds, but most of them fail to grow pods and abort during development. Many studies indicated promotive effects of exogenously applied cytokinin on pod setting, but the effects of auxin application on pod set are ambiguous. In this study, we examined the changes in the concentrations of endogenous auxin and cytokinin in racemes and the effects of application of the two hormones on pod setting to clarify the role of auxin and cytokinin in soybean pod setting. The long-raceme soybean genotype IX93-100 was grown in pots and in the field. The auxin (IAA, indoleacetic acid) concentration in racemes was high for a long period from pre-anthesis to 9 days after anthesis (DAA) of the first flower on a raceme, but the cytokinin concentration was high for a short period, with a peak at 9 DAA. The IAA concentration was higher in distal portions of racemes, but the cytokinin concentration was higher in basal portions of racemes. In pot-grown plants, IAA applied to racemes tended to reduce the number of flowers and pods. In contrast, 6-benzylaminopurine (BA) applied to racemes before anthesis tended to reduce the number of flowers and pods, and that applied around 7 DAA significantly increased the pod-set percentage. However, these effects of IAA and BA application were slight in field-grown plants. These results indicate that the concentration of endogenous auxin and cytokinin in racemes changes in a different manner, and that cytokinins have a positive, and auxin a negative effect on pod setting when respective hormones are applied to racemes after the anthesis stage.

The Occurrence of Delayed Stem Senescence in Relation to trans-Zeatin Riboside Level in the Xylem Exudate in Soybeans Grown under Excess-Wet and Drought Soil Conditions

Delayed stem senescence (DSS) after pod maturation in soybean (Glycine max) lowers the quality of products in the mechanized harvest. The effects of drought and excess wet soil conditions on the occurrence of DSS were studied with special reference to remobilization of vegetative nitrogen and supply of cytokinin via xylem. Excess wet soil treatment was applied throughout the reproductive period to field-grown soybean in 2003 (Exp.1) and short-term drought stress treatment was applied during the reproductive period to pot-grown soybean plants in 2004 (Exp.2). The degree of DSS at pod maturing was evaluated by the DSS score from “1” for severe DSS to “5” for completely synchronous senescence of pods and vegetative parts. The DSS score in Exp.1 varied from 2.2 to 2.5 and that in Exp.2 from 2.8 to 3.7. Excess wet soil treatment in Exp.1 promoted the occurrence of DSS, while drought stress treatments during the periods of flowering to pod elongation, later seed-filling and seed maturing decreased it. The soybean plants that showed distinct DSS had lower ratios of seed number to vegetative dry weight at seed maturity and a lower rate of nitrogen remobilization from vegetative organs to seeds during the latter half of the reproductive period. The trans-zeatin riboside (t-ZR) level in xylem exudate tended to be higher in soybeans with severer DSS than in those normally matured in both experiments showing increased t-ZR concentration and/or higher exudation rate. These results suggest that DSS can be caused by a wet soil water condition, which lowers pod/seed number and increases vegetative organs mediated by the increased supply of cytokinin through xylem during seed-filling.

Volatile organic compounds in the roots and rhizosphere of Pinus spp.

Plant roots normally release a complex mixture of chemicals which have important effects in the rhizosphere. Among these different root-emitted compounds, volatile isoprenoids have received very little attention, yet they may play important and diverse roles in the rhizosphere, contributing to the regulation of microbial activity and nutrient availability. It is therefore important to estimate their abundance in the rhizosphere, but so far, there is no reliable sampling method that can be used to measure realistic rates of root emissions from plants growing in field conditions, or even in pots. Here, we measured root content of volatile isoprenoids (specifically monoterpenes) for Pinus pinea, and explored the feasibility of using a dynamic bag enclosure method to measure emissions from roots of intact pot-grown plants with different degrees of root cleaning. We also investigated a passive diffusion method for exploring monoterpenes in soil at incremental distances from mature Pinus sylvestris trees growing in field conditions. Total monoterpene content of P. pinea roots was 415±50 μg g −1 fresh wt in an initial screening study, and between 688±103 and 1144±208 μg g −1 dry wt in subsequent investigations. Emissions from shaken-clean roots of intact plants and roots of intact plants washed to remove remaining soil after shaken-clean experiments were 119±14 and 26±5 μg g −1 dry wt h −1, respectively. Emissions from intact roots in soil-balls were an order of magnitude lower than from shaken-clean roots, and probably reflected the amount of emitted compounds taken up by physical, chemical or biological processes in the soil matrix surrounding the roots. Although monoterpene content was not significantly different in droughted roots, emission rates from droughted roots were generally significantly lower than from well-watered roots. Finally, passive sampling of monoterpenes in the soil at different distances from mature P. sylvestris trees in field conditions showed significantly decreasing sampling rates with increasing distance from the trunk. We conclude that it is feasible to measure volatile isoprenoid emissions from roots but the method of root preparation affects magnitude of measured emissions and therefore must be decided according to the application. We also conclude that the rhizosphere of Pinus species is a strong and previously un-characterized source of volatile isoprenoid emissions and these are likely to impact significantly on rhizosphere function.

Nitrogen fertilizer and gender effects on the secondary metabolism of yaupon, a caffeine-containing North American holly

Yaupon (Ilex vomitoria) is a caffeine-containing dioecious shrub native to the southeastern United States that was historically brewed into a stimulating beverage. We tested predictions of the carbon/nutrient balance (CNB) hypothesis by determining whether nitrogen availability and gender influence production of caffeine and related alkaloids as well as phenolic compounds in leaves of pot-grown yaupon plants fertilized with ammonium nitrate. The CNB hypothesis predicts that additional nitrogen should result in increased alkaloid concentrations and decreased phenolic concentrations. An extension of the CNB hypothesis to dioecious plants predicts that females have higher C/N ratios and therefore higher phenolic concentrations and lower alkaloid concentrations than male conspecifics. In our study, caffeine and total alkaloid concentrations were 5-10 times higher in fertilized than control plants but did not vary by gender. Nevertheless, an observed interaction between gender and fertilization suggests that females respond more to fertilization than males in caffeine production. In addition, fertilized plants not only contained higher concentrations of alkaloids and total nitrogen but also allocated a larger proportion of their nitrogen to alkaloid production than control plants. Total phenolic concentrations were higher in control females than control males as predicted by the CNB hypothesis, but did not vary by treatment nor were there differences by gender among fertilized plants. We also found high correlations between antioxidant capacity and both classes of phenolic compounds detected in our study (cinnamic acid derivatives and flavonoids) indicating that in addition to their putative defensive function against herbivores, phenolics protect yaupon from oxidative stress. Explanation of the inconsistencies between our data and predictions of the CNB hypothesis may benefit from a re-appraisal of the physiological mechanisms by which resource availability affects secondary metabolism as well as consideration of the selective pressures to which secondary metabolism responds.

Overview and Forecast on Forestry Productions Worldwide

Air pollution has been identified as a serious problem throughout the world which causes tremendous loss to the crops by affecting plant growth and yield. Earlier, air pollution was restricted to urban and industrial regions. Over the last few decades, however, it has become evident that pollutants can be transported over long distances and hence their impact may be felt widely over rural areas. The present study was conducted to evaluate the impact of urban air pollution on suburban agriculture with respect to the changes in photosynthetic rate, stomatal conductance, water-use efficiency, plant height, numbers of tillers, leaves, ears and seeds, chlorophyll, carotenoid, protein, phenol, ascorbic acid, nitrogen and sulphate-sulphur contents and seed weight of pot-grown wheat plants (Triticum aestivum var. HUW 468) kept at different sites around Varanasi city receiving varying levels of pollution load. Mean concentrations of SO2, NO2 and O3 were monitored. The study clearly showed that plants are negatively affected by the ambient levels of air pollutants. Reduction in various parameters directly corresponded with the air pollution levels at different sites.

An experimental approach to quantifying chemical and positional availability of soil potassium

We propose a new experimental approach that enables to evaluate the chemical and positional availability of soil potassium (K) to pot-grown plants. The proposed approach makes use of the inherent differences between the removal of soil K by plants and by chemical methods, and comprises the following procedures: 1) preparation of both planted and unplanted soils by conducting a pot experiment; 2) stepwise extraction of K in these soils with neutral 1 M NH4OAc, followed by repeated treatment with 0.01 M HCl; and 3) calculation of the chemical and positional availability of K by determining the amount of K removed in each step of extraction. By applying this method to K-bearing minerals and a Fluvisol sampled from pots in which wheat (Triticum aestivum L.) and komatsuna (Brassica campestris L. var. rapa) had been grown for 30 d, we could estimate that more than half of the exchangeable K in a pot was located within the range of root removal (positionally available), and that the percentage of K in a positionally available form decreased with the decrease in its chemical availability. Furthermore, the application of this method to other published data convinced us that, in principle, the method is applicable to all the pot-grown plants and also to various soils and minerals. Since the proposed approach does not require a special pot for regulating root growth, it may further provide a clue for the development of a quantitative field method.