Quartz Sand Culture Research Articles

Study on burrowing nematode, Radopholus similis, pathogenicity test system in tobacco as host

Radopholus similis (Cobb 1893) Thorne (1949) is a destructive migratory endoparasitic plant nematode. In this study, the pathogenic process of R. similis infection in Nicotiana benthamiana (tobacco) was studied using quartz sand culture in laboratory. The results showed that R. similis mainly parasitised the root cortex, leading to cortical cell decomposition and tissue decay. We optimised the inoculation conditions to establish a method for determining the pathogenicity of R. similis as follows: (1) a glass culture tube was filled with quartz sand (about 1/3 of the height) and sterilised twice; (2) 20-day-old N. benthamiana seedlings were transplanted into test tubes and cultivated for 10 days at (25±1)°C; (3) R. similis female nematodes were inoculated in the root rhizosphere at a rate of 150 nematodes per plant; (4) the number of nematodes, disease severity, and growth of the plant at 30 days post-inoculation (dpi) were determined. The pathogenicity of eight R. similis populations from different hosts was determined, which proved the feasibility of this method.

Effects of StP5CS gene overexpression on nodulation and nitrogen fixation of vegetable soybean under salt stress conditions

Using a quartz sand culture, comparisons were made between the T5 homozygous transgenic lines (HTLs) that overexpress StP5CS (GenBank accessionnumber: JN606861) and their wild-type (WT)host cultivar to examine thedifferences inthe growth and development traits, the concentrations of proline in vegetable soybean [Glycine max (L.) Merrill] under salt stress conditions. Moreover, the relative expression levels of two glutamine synthetase-related genes (GmGS1β1, GmGS1β2), two nodulation-related genes (GmENOD40-1, GmENOD40-2), and one leghemoglobin gene (GmLba) were also measured. The purposeof this research wasto provide a theoretical basis forelucidatingthe mechanisms ofnodulation andnitrogen fixation in the roots of transgenic plants under salt stress conditions. Compared with WT plants, the plant height and seed weight per plant of T5 HTLs significantly increased, and the contents of proline in various tissues of T5 HTLs were also significantly elevated. Quantitative real-time PCR (qRT-PCR) analysis indicated that the expression levels of GmGS1β1, GmGS1β2, GmENOD40-1, GmENOD40-2, and GmLba were significantly increased in T5 HTLs under salt stress conditions. These results indicate that the overexpression of StP5CS in T5 HTLs enhanced growth, nodulation and nitrogen fixation in transgenic vegetable soybean under salt stress conditions.

Effects of magnesium remobilization and allocation on banana plant growth

ABSTRACTMagnesium (Mg) is known as one of the mobile elements and can move from the lower to upper leaf blade when the plants suffer from Mg deficiency. It is generally recognized that symptoms of Mg deficiency appear on lower leaves. This study was conducted to reveal the effect of Mg deficiency stress on remobilization of Mg and nitrogen in banana plant and to collect the typical symptoms of Mg deficiency. Quartz sand cultures were used to study the effect of Mg deficiency on banana growth and its mobilization and allocation in the plants. Results showed that chlorosis, a typical symptom of Mg deficiency, occurs in the second leaf from top of banana plant after 35 days of Mg deficiency. Necrosis of the whole leaf in the middle part of banana and a significant reduction of leaf area from the top to middle leaves are detected. However, older leaves remain green, and their area is not affected. Mg is more stable in the banana plant and cannot be remobilized and transported from the old to young leaves under Mg deficiency. After 195 days of Mg deficiency, the growth and Mg nutrition of Mg-deficient plant can be normalized by the restoration of Mg nutrient after 49 days of deficiency. Therefore, Mg in banana leaves is not mobile and reusable from older to younger leaves.

The role of phosphorus deficiency in nodule microbial composition, and carbon and nitrogen nutrition of a native legume tree in the Cape fynbos ecosystem

In phosphorus (P)-poor ecosystems, microbial communities can play a major role in the nitrogen (N) mineral nutrition during N2 fixation in legumes. This study investigated the role of P nutrition on the composition of N2-fixing bacterial community in Virgilia divaricata root nodules, grown under glasshouse conditions. V. divaricata seeds were germinated in Fynbos soil as a natural inoculum, and, thereafter, transferred into sterile quartz-sand cultures and supplied with 500 µM P and 5 µM P, respectively. The N2-fixing bacterial communities in the rhizosphere and root nodules were examined on the basis of the polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) banding patterns of 16S rDNA and sequencing methods. The GenBank blast results showed that V. divaricata was nodulated by a wide range of root-nodule bacterial strains also found in the rhizosphere. These included Burkholderia phytofirmans, Burkholderia sp. and Bradyrhizobium sp., during both high and low P supply. The 15N natural-abundance data also confirmed that 40–50% of the N nutrition was from symbiotic N2 fixation. This is not only evidence of nodulation, but an indication of the adaptation of a range of N2-fixing bacterial strain species to the nutrient-poor, sandy, acidic soil of the Mediterranean-type ecosystems of the fynbos vegetation in the Cape Floristic Region (CFR). Legume species V. divaricata is highly adapted to the low-nutrient soils of its native range by its association with the symbiotic N2-fixing bacteria.

Waste silicate minerals as potassium sources: a greenhouse study on spring barley

After 1989, the use of potassium (K) mineral fertilizers in the Czech Republic dropped from ∼55 kg K ha−1 to a mean rate of ∼6.5 kg in the last decade. In order to test alternative solutions for K fertilization, the trioctahedral mica mineral zinnwaldite (8% K), orthoclase (10% K) and waste mica from Cínovec (Krušné Hory Mts/Erzgebirge, Czech Republic), consisting primarily of zinnwaldite, were applied as the only K sources for spring barley. The minerals were treated in three different types of high-energy mills under different working conditions. Application rates in the range 139–820 mg K kg−1 were tested in quartz sand cultures. In all treatments, plant growth, total plant biomass and the K content in the plant tissues increased in the order zinnwaldite > waste mica > orthoclase. K fractionation and K plant uptake were significantly influenced by the milling method used. The effect of 195 mg K kg−1 as zinnwaldite on K uptake from K-depleted soils was positive; however, it was smaller than in sand cultures because of the relatively high content of non-exchangeable K in the soils. Direct use of waste mica as a K fertilizer is limited by the increased fluorine and heavy metal content.

Overexpression of phyA and appA genes improves soil organic phosphorus utilisation and seed phytase activity in Brassica napus.

Phytate is the major storage form of organic phosphorus in soils and plant seeds, and phosphorus (P) in this form is unavailable to plants or monogastric animals. In the present study, the phytase genes phyA and appA were introduced into Brassica napus cv Westar with a signal peptide sequence and CaMV 35S promoter, respectively. Three independent transgenic lines, P3 and P11 from phyA and a18 from appA, were selected. The three transgenic lines exhibited significantly higher exuded phytase activity when compared to wild-type (WT) controls. A quartz sand culture experiment demonstrated that transgenic Brassica napus had significantly improved P uptake and plant biomass. A soil culture experiment revealed that seed yields of transgenic lines P11 and a18 increased by 20.9% and 59.9%, respectively, when compared to WT. When phytate was used as the sole P source, P accumulation in seeds increased by 20.6% and 46.9% with respect to WT in P11 and a18, respectively. The P3 line accumulated markedly more P in seeds than WT, while no significant difference was observed in seed yields when phytate was used as the sole P source. Phytase activities in transgenic canola seeds ranged from 1,138 to 1,605 U kg–1 seeds, while no phytase activity was detected in WT seeds. Moreover, phytic acid content in P11 and a18 seeds was significantly lower than in WT. These results introduce an opportunity for improvement of soil and seed phytate-P bioavailability through genetic manipulation of oilseed rape, thereby increasing plant production and P nutrition for monogastric animals.

油菜对Sr胁迫的生理生态响应

在砂培条件下，采用不同浓度的Sr2+ (0、05、1、5、10 mmol/L)对转pprI基因油菜幼苗(Brassica napus L.)和非转基因油菜幼苗处理30 d，分析油菜幼苗对Sr的吸收积累情况，并研究油菜对Sr胁迫的生理生态响应。结果表明：转基因油菜幼苗和非转基因油菜幼苗对Sr2+的吸收量均随Sr2+胁迫浓度的升高而升高，转基因油菜根部的Sr2+含量大于非转基因油菜根部，而地上部分的Sr2+含量却小于非转基因油菜。与对照相比，在Sr2+胁迫下的转基因油菜和非转基因油菜脯氨酸(Pro)含量则随Sr2+浓度的提高而升高，而SOD、POD活性和叶绿素含量都随Sr2+浓度的增加呈先上升后下降趋势。与非转基因油菜相比，转基因油菜在各种胁迫浓度下的SOD、POD活性、叶绿素含量以及脯氨酸含量都高于非转基因油菜。因此得出结论：转pprI基因油菜较非转基因油菜更具有对Sr胁迫的抗性和耐受能力。 PprI-transgenic and non-transgenic rape seedlings (Brassica napus L.) were treated with different concentrations of Sr2+ (0, 0.5, 1, 5, 10 mmol/L) for 30 days under quartz sand culture. The Sr2+ uptake and physiological and ecological characteristics of rape seedlings were investigated. The results showed that the uptake of Sr2+ in transgenic and non-transgenic rape seedlings increased with the increase of Sr2+ stress concentration; the content of Sr2+ in transgenic rape roots was greater than that in non-transgenic, but the content in up-ground parts in transgenic rape was less than that in non-transgenic rape. Contrasted to the CK, the content of Pro increased with the increase of Sr2+ concentration, but the activity of SOD and POD, and the content of chlorophyll first increased then declined. Under the same treatment, the activity of antioxidant enzymes (SOD and POD) and the content of chlorophyll and Pro in transgenic rape were higher than those in non-transgenic rape. So we conclude that: PprI-transgenic rape has better ability of resistance and tolerance to strontium-stress.

Biodegradation of polyvinyl alcohol by Flammulina velutipes in an unsubmerged culture

To examine the biodegradation of polyvinyl alcohol (PVA), Flammulina velutipes (Enokitake) was cultivated in both liquid and quartz sand cultures. After incubation, discoloration of an iodide solution was observed in the filtrate recovered from the quartz sand culture, whereas discoloration was not observed in the filtrate recovered from the liquid culture. Gel permeation chromatography showed that the PVA recovered from the quartz sand culture was depolymerized and yielded low-molecular-weight portions. Infrared and ultraviolet spectrometry indicated that there was formation of carbonyl groups, and NMR analysis showed that the syndiotactic portions of PVA were preferably attacked. Based on these results, an unsubmerged cultivation of F. velutipes was considered suitable for the biodegradation of PVA, probably because the mycelium was sufficiently developed to produce PVA-degrading enzymes.

Genetic Variability in Phosphorus Acquisition and Utilization Efficiency from Sparingly Soluble P‐Sources by Brassica Cultivars under P‐Stress Environment

AbstractPlants display an array of classical strategies to maximize phosphate (Pi) acquisition from sparingly soluble P sources. Acclimation to Pi‐stress via elegant Pi‐starvation induced (PSI) adjustments would reduce our current overreliance on expensive, polluting and non‐renewable Pi‐fertilizers. Nevertheless, differences in the ability of various species to solubilize sparingly soluble P‐sources have been often evidenced; inter‐cultivar variations are scarcely documented. Brassica is known as an effective, non‐mycorrhizal user of sparingly soluble P‐sources. Various growth parameters and biomass accumulation by genetically diverse Brassica cultivars were determined in four experiments using hydroponics and quartz sand culture media. Role of PSI root mediated pH changes, organic anions (OAs) exudation and altered root architecture in mobilization and acquisition of sparingly soluble P‐forms [Jordan rock‐P (RP) at 2 g l−1 and Ca3(PO4)2 (TCP) at 0.2 g l−1 respectively] was investigated. Cultivars showed considerable genetic variations in biomass accumulation, various growth parameters and root–shoot ratio. Concentration and total uptake of P, specific absorption rate of P, P‐transport rate and P‐utilization efficiency (PUE) were also significantly (P < 0.001) different for various cultivars and their dry matter was significantly correlated with P‐uptake [r = 0.94** (significant at 1% level)]. P‐tolerant cultivars showed substantial decrease in solution media pH because of H+ efflux and exuded more carboxylates than low P‐sensitive cultivars under P‐starvation. P‐uptake by cultivars increased linearly with decreasing pH. The amount and types of OAs exuded from the roots of P‐starved plants differed from those of plants grown under P‐sufficient environment. In split pot study, with TCP and RP supplied spatially separated from other nutrients, efficient cultivars were still able to mobilize RP and TCP more efficiently than inefficient cultivars. In rhizobox study, the elongation rates of primary roots decreased but the elongation rates of the branched zones of primary roots and the length of lateral roots increased under P‐starvation. Tested cultivars showed genetic diversity in accessing, mobilization, acquisition and utilization of Pi from sparingly soluble P forms. An arrange marriage of plant traits can explain cultivar’s access to different forms of sparingly soluble P, and in addition to altered lateral root topology and enhanced P‐uptake and PUE, enhanced H+ efflux and OAs exudation are key factors in Pi scavenging from extra cellular sparingly soluble P‐forms.

Studies on the sources of benzo[ a]pyrene in grain and aboveground tissues of rice plants

Rice plant pot experiments designed to identify benzo[ a]pyrene (B[ a]P) sources in plant tissues were conducted in an air-quality controlled greenhouse built to prevent contamination from B[ a]P air pollution. Results from quartz sand cultures with control and 50, 100 and 500 μg kg −1 of B[ a]P treatments were compared with those from outdoor field experiments, in which rice plants were exposed to polluted air in the urban area of Shenyang, China. When B[ a]P was strictly controlled in both air and quartz sand culture medium, the background values of B[ a]P in rice plant tissues were uniformly very low. There was no significant difference of B[ a]P contents of rice grain between control and treatments of B[ a]P in controlled air quality trials. This indicated that the source of B[ a]P in the rice grains is not from any B[ a]P in the root culture media. The B[ a]P content of rice grain, husk, and stem with leaf sampled from outdoor field was up to 7.33-, 9.21- and 27.10-fold higher than corresponding tissues from air-quality controlled conditions. This indicated that polluted air is the main source of B[ a]P in aboveground tissues. Therefore control of B[ a]P pollution in ambient air is of prime importance for improving the quality of cereal crops.

Impact assessment of cadmium contamination on rice (Oryza sativa L.) seedlings at molecular and population levels using multiple biomarkers

Assessment of environmental contamination on ecology (plant) at molecular and population levels is important in risk quantification and remediation study. Random amplified polymorphic DNA (RAPD) assay and related other fingerprinting techniques have been employed to detect the genotoxin-induced DNA damage and mutations. This research compared the effects occurring at molecular and population levels in rice seedlings exposed to cadmium (Cd) concentrations of 15-60 mg l(-1) for 8 days with quartz sand culture. Inhibition of root growth and increase of total soluble protein content in root tips of rice seedlings were observed with the increase of Cd concentration. For the RAPD analyses, 12 RAPD primers of 50-70% GC content were found to produce unique polymorphic band patterns and subsequently were used to produce a total of 180 bands of 179-3056 bp in molecular size in the control root tips of rice seedlings. Results produced by these RAPD primers indicate that changes in RAPD profiles of root tips after Cd treatment include modifications in band intensity and gain or loss of bands by comparison with control. The effect of changes was dose-dependent. Genomic template stability compares favourably with the traditional indices such as root growth and soluble protein content. The DNA polymorphisms detected by RAPD analysis can be applied as a suitable biomarker assay for the detection of genotoxic effects of Cd contamination on plants.

Genetic variability in tolerance to cadmium and accumulation of heavy metals in pea (Pisum sativum L.)

Summary Ninety-nine wild growing and primitive varieties of garden pea (Pisum sativum L.) were screened for tolerance to cadmium (Cd) toxicity in quartz sand culture. Cadmium tolerance was determined by the time to plant death when treated with a lethal Cd concentration (13 mg kg −1 ), and by a tolerance index (TI) calculated as a ratio between biomasses of Cd-treated and untreated plants in the presence of toxic Cd concentrations (7 mg kg −1 and 5m g kg −1 ). The Cd-tolerance index varied significantly between pea genotypes from 35% to 90% and from 54% to 100% in the presence of 7 and 5 mg Cd kg −1 , respectively. Shoot Cd concentration of tolerant and sensitive genotypes grown in the presence of 5 mg Cd kg −1 varied between 35 mg Cd kg −1 and 135 mg Cd kg −1 (dry weight) and was negatively correlated with TI. Certain tolerant pea genotypes were characterised by a high Cd concentration in shoots. All varieties were also screened for their ability to take up heavy metals (HMs) from a slightly contaminated soil. The concentration of Cd, chromium, copper, nickel, lead, strontium and zinc in plant shoots varied between pea genotypes by a factor of 2.8, 4.9, 2.7, 3.5, 9.7, 3.9 and 4.0, respectively. The coefficients of variation between pea genotypes for HM concentration were high, varying from 23% to 39% depending on the metal. The distribution patterns for varieties based on Cd tolerance (sand culture) and HM concentrations (soil culture) were characterised by positive skewness coefficients, suggesting that the majority of pea genotypes was relatively sensitive to Cd toxicity and tended to avoid excessive accumulation of HMs in shoots. These results show that a high genetic variability exists in pea with regards to Cd tolerance and HM accumulation. Concentrations of different HMs in plants grown in soil correlated positively with each other, with the exception of chromium. There was no correlation between Cd tolerance of the varieties in sand culture, shoot concentration of HMs in soil culture, biomass production, subspecies and geographical origin of the varieties. The genetic systems controlling Cd tolerance, HM accumulation and morphological traits are therefore independent to some extent, suggesting a possibility for breeding pea cultivars characterised by high tolerance to and low concentration of HMs in shoots.

Effect of associative bacteria on element composition of barley seedlings grown in solution culture at toxic cadmium concentrations

The response of barley seedlings to inoculation with associative rhizobacteria Azospirillum lipoferum 137, Arthrobacter mysorens 7, Agrobacterium radiobacter 10 and Flavobacterium sp. L30 was studied in hydroponic and quartz sand cultures in the presence of 50 μM CdCl 2. Cadmium caused severe inhibition in the growth and uptake of nutrient elements by the plants. Inoculation with the bacteria slightly stimulated root length and biomass of hydroponically grown Cd-treated seedlings. The bacteria increased the content of nutrients such as P, Mg, Ca, Fe, Mn and Na in roots and or shoots of the plants grown in the absence of Cd. Positive changes in the element composition caused by the bacteria were less pronounced in Cd-treated plants, whereas the total amount of nutrients taken by the inoculated plants was generally increased significantly. The content of Cd in the inoculated plants was unchanged, except increased in roots upon addition of A. lipoferum 137. Inoculation did not affect the activity of peroxidase, α-mannosidase, phosphodiesterae, α-galactosidase, and concentration of sulfhydryl compounds used as biochemical markers of stress in plant roots. The results showed that associative bacteria were capable of decreasing partially the toxicity of Cd for the barley plants through the improvement in uptake of nutrient elements.

Sink-stimulated photosynthesis, increased transpiration and increased demand-dependent stimulation of nitrate uptake: nitrogen and carbon relations in the parasitic associationCuscuta reflexa-Coleus blumei

When parasitizing Coleus blumei Benth., grown in quartz sand culture and fed with 0.2,1 or 5 mM nitrate, the biomass production of Cuscuta reflexa Roxb. was inhibited to a similar extent as that of the host supplied limiting concentrations of nitrate. In the presence of Cuscuta the growth and dry matter increase of the host plant was severely inhibited. However, dry matter production of host plus parasite was only slightly less than or at 0.2 mM nitrate almost the same as that of uninfected Coleus plants. Under all conditions of nitrate nutrition, parasitism by Cuscuta led to a substantial increase in photosynthesis in host leaves under light-saturating conditions and in transpiration . Particularly with 0.2 mM and mM NO 3~ parasitism by Cuscuta reflexa also led to an increase in the nitrogen concentration in almost all host tissues and to a substantial increase in the chlorophyll concentration of leaves. The total nitrogen content in the system, host plus parasite, was as large with 0.2 and 1 mM NO3 or only somewhat smaller with 5 mM NO3~ than that of the unparasitized host. Since the root weight of infected plants was considerably decreased, it followed that nitrate uptake by roots of parasitized plants was substantially increased compared to the uninfected Coleus. Increased photosynthesis and accelerated nitrate uptake are discussed in relation to an increased sink for assimilates and to higher demand for nitrogen in the parasitized plants and to opposing effects of Cuscuta on symbioticalty nitrogen-fed hosts.

Growth of Zea mays L. plants with their seminal roots only. Effects on plant development, xylem transport, mineral nutrition and the flow and distribution of abscisic acid (ABA) as a possible shoot to root signal

Maize (Zea mays L.) was grown in quartz sand culture either with a normal root system (controls) or with seminal roots only ('single-rooted'). Development of adventitious roots was prevented by using plants with an etiolated mesocotyl and the stem base was positioned 5-8 cm above the sand. Even though the roots of the single-rooted plants were sufficiently supplied with water and nutrients, the leaves experienced water deficits and showed decreased transpiration as transpirational water flow was restricted by the constant number of xylem vessels present in the mesocotyl. As a consequence of this restriction, transpirational water flow velocities in the metaxylem vessels reached mean values of 270 m h -1 and phloem transport velocities of 5.2 m h -1 . Despite limited xylem transport mineral nutrient concentrations in leaf tissues were not decreased in single-rooted plants, but shoot and particularly stem development was somewhat inhibited. Due to the lack of adventitious roots the shoot:root ratio was strongly increased in the single-rooted plants, but the seminal roots showed compensatory growth compared to those in control plants. Consistent with decreased leaf conductance, ABA concentrations in leaves of single-rooted plants were elevated up to 10-fold, but xylem sap ABA concentrations in these plants were lower than in controls, in good agreement with the well-watered conditions experienced by the seminal roots. Surprisingly, however, ABA concentrations in tissues of the seminal roots of the single-rooted plants were clearly increased compared to the controls, presumably due to increased ABA import via phloem from the water-stressed leaves. The results are discussed in relation to the role of ABA as a shoot to root signal.

Sink‐stimulated photosynthesis and sink‐dependent increase in nitrate uptake: nitrogen and carbon relations of the parasitic association Cuscuta reflexa–Ricinus communis

ABSTRACT Ricinus communis L. was grown under limiting N supply in quartz sand culture, fed with 0.2, 1 or 5 mol m−3 NO3−, or in liquid culture with 0.022, 0.05 or 0.5 mol m−3 NO3−. Some of the plants were infected with Cuscuta reflexa Roxb. As occurred for the host, dry matter production and growth of C. reflexa were severely depressed with decreasing N supply to the host. When parasitized by C. reflexa, the shoot and root dry weight of Ricinus was diminished at all levels of N nutrition, but the total dry weight of host plus parasite was almost the same as that of uninfected Ricinus. In contrast to the situation in Lupinus albus (Jeschke et al. 1994b), infection by Cuscuta resulted in increased tissue N levels in the host and the N content of the system Ricinus plus C. reflexa was the same or even somewhat larger than that of uninfected plants. This indicated a sink‐dependent stimulation of nitrate uptake. As a result of decreased root weights, nitrate uptake g−1 FW was stimulated by 80, 60 or only 40% at 0.2, 1 or 5 mol m−3 nitrate supply. Increased nitrate uptake was reflected, particularly at low N supply, in xylem transport; xylem sap nitrate concentrations were substantially elevated, while those of amino acids were decreased in parasitized plants. This indicated an inhibition of nitrate assimilation in roots of parasitized plants under limiting N supply. Besides these effects on N relations, C. reflexa induced a substantial sink‐dependent stimulation of net photosynthesis in host leaves and a concomitant increase in stomatal opening and transpiration. This stimulation depended on the relative sink size induced by Cuscuta, on nitrogen nutrition and on leaf age, indicating that delayed senescence of leaves contributes to the overall effects of Cuscuta on its host. The Cuscuta‐induced inhibition of nitrate assimilation in the roots and the increase in nitrate uptake suggest that nitrate reduction was shifted towards the leaves in the presence of C. reflexa. The stimulating effects of C. reflexa in the Ricinus‐Cuscuta association are compared with the strongly inhibitory effects occurring in the tripartite association L. albus–Rhizobium–Cuscuta reflexa.

POLYAMINE ACCUMULATION BY TOMATO PLANTS UNDER NUTRITIONAL STRESS

Polyamine accumulation is a response of plants to various environmental stresses. Polyamine accumulation was assessed in relation to ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.) under nutritional stress. Nutritional stresses were imparted on plants grown in quartz sand culture under greenhouse conditions with NH4-based modified Hoagland's solution or with NO3-based solutions without P, K, Ca, or Mg. The plants receiving NH4 nutrition were grown with or without 10-5 M (aminooxy)acetic acid (AOA) or 10-5 M silver thiosulfate (STS). Plants on nutrient deficient solution were grown with or without the AOA. When plants appeared with toxic or deficient symptoms, the new fully expanded leaves were collected and extracted by 5% perchloric acid for polyamine analyzes by HPLC. Plants receiving NH4-based nutrition had high putrescine and low spermidine concentrations. High spermidine and low putrescine concentrations occurred in plants receiving complete NO3-based nutrition. For plants receiving NH4-based nutrition, application of AOA suppressed accumulation of putrescine but had no effect on spermidine, and STS had no effect on polyamine accumulation. For plants receiving NO3-based nutrition without P, K, Ca, or Mg, the application of AOA restricted accumulation of putrescine and spermidine. High putrescine concentration was accompanied by high ammonium accumulation, high ethylene evolution, and stressinduced symptoms, indicating an association between polyamine accumulation and other stress-related phenomena.

Structural changes in conifer needles due to Mg and K deficiency

Needles from Norway spruces (Picea abies Karst.) with symptoms of Mg- or K-deficiency were investigated anatomically. Besides pronounced changes in the structure of the chloroplasts and partial accumulation of starch in the mesophyll cells, premature necrosis and collapse of the sieve cells in the vascular bundles was the most pronounced structural symptom. The same pattern of development was found in yellow needles of mature trees in the field with symptoms of ‘new-type forest decline’ as in needles from young trees grown in quartz-sand culture with controlled induction of deficiencies. The possible consequences of these structural symptoms for the physiology of trees growing under these deficiencies and their involvement in recent ‘forest decline’ are discussed.

Effects of potassium deficiency and simulated acid rain, alone and in combination, on the ultrastructure of Scots pine needles

The effects of potassium deficiency and artificial acid precipitation, alone and in combination, on Scots pine (Pinussilvestris L.) needles were studied using transmission electron microscopy. The seedling material was grown in quartz sand culture and watered with nutrient solution containing 45, 20, 10, or 5 mg of potassium/L; the concentration of other nutrients was constant and equally available for all seedlings. A portion of the seedlings from each group received consecutive acidified water spraying of pH 4.5, 4.0, 3.5, and 3.0, each for 4 days with a 3-day resting period between applications. The potassium deficiency caused an increase in the proportional vacuolar space and severe vesiculation of the tonoplast. Irregularly shaped lipid structures increased in number in the cytoplasm, and lipid bodies also appeared in the vacuoles and occasionally in the chloroplasts. The symptoms related to potassium deficiency were more severe in the transfusion parenchyma cells than in the mesophyll. The lowest level of potassium produced almost complete disorganization of the cellular structures in the transfusion parenchyma tissue, but severe changes were also seen in the mesophyll. The simulated acid rain treatment caused the formation of protrusions in the chloroplasts and an increase in irregularly shaped lipid structures in the cytoplasm throughout the mesophyll tissue, but no clear symptoms were observed inside the bundle sheath. In general, the changes caused by acid rain in the chloroplasts were slight and did not cause serious disorganization of these organelles. When the seedlings were exposed to combination treatment, the typical symptoms of both exposures were observable. The results suggest that the stresses caused by potassium deficiency and short-term foliar acid rain treatment can be distinguished in the needle ultrastructure.

Uptake of amino acids by plants from the soil: A comparative study with castor bean seedlings grown under natural and axenic soil conditions

Castor bean seedlings grown in different media (soil, quartz sand, or liquid culture) under natural or axenic conditions take up14C labelled proline when offered to the rooting medium at concentrations similar to those occuring in the soil. Most of the absorbed proline was transferred through the root into the xylem without metabolic conversion, though some conversion to glutamine and alamine occurred.