Sand Culture System Research Articles

Nitrogen and phosphorus acquisition by the mycelium of the ectomycorrhizal fungus Paxillus involutus and its effect on host nutrition.

The contribution of the extramatrical mycelium to N and P nutrition of mycorrhizal Norway spruce (Picea abies (L.) Karst.) was investigated. Seedlings either inoculated with Paxillus involutus (Batsch) Fr. or non-mycorrhizal were grown in a two compartment sand culture system where hyphae were separated from roots by a 45 μm nylon net. Nutrient solution of the hyphal compartment contained either 1.8 mm NH4 + and 0.18 mm H2 PO4 - or no N and P. Aluminium added to the hyphal compartment as a tracer of mass flow was not detected in the plant compartment, indicating that measurements of N and P transfer by the mycelium were not biased by solute movement across the nylon net. The addition of N and P to the hyphal compartment markedly increased dry weight, N and P concentration and N and P content of mycorrhizal plants. Calculating uptake from the difference in input and output of nutrient in solution confirmed a hyphal contribution of 73% and 76% to total N and P uptake, respectively. Hyphal growth was increased at the site of nutrient solution input.

Effect of Nitrogen Source on Carbohydrates Allocation and Nitrogen Assimilation in Nerium oleander L. under Salt Stress.

The effects of ammonium and nitrate as the nitrogen source on concentration of NO3--N, NH4+-N, amino acids, protein, carbohydrates and site of nitrogen assimilation were studied in Nerium oleander L. under NaC1 salinity. Plants were grown in semi automatic sand culture system in the green house. We distinguished different distribution of carbohydrates and amino acids by nitrogen source under salinity. Ammonium and amino acids concentration increased in roots of ammonium treatment by salinity whereas protein concentration decreased. The level of carbohydrates decreased in leaves and increased in roots by salinity in ammonium treatment. No significant change in level of amino acids and carbohydrates was observed in nitrate treatment due to salt stress. Based on concentration of NO3--N, NH4+-N in xylem sap, glutamine synthetase and nitrate reductase activity, nitrogen assimilation was mostly done in roots and leaves in ammonium and nitrate treatments respectively. The lower tolerance of ammonium fed plants than nitrate is mostly related to higher diversion of carbohydrates from structure production to roots for ammonium detoxification and osmotic adjustment in ammonium fed plants under salinity.

Interactions between the soilborne root pathogenPhytophthora nicotianae var.parasitica and the arbuscular mycorrhizal fungusGlomus mosseae in tomato plants

In order to study the influence of Arbuscular Mycorrhiza (AM) on the development of root rot infection, tomato plants were raised with or withoutGlomus mosseae and/orPhytophthora nicotianae var.parasitica in a sand culture system. All plants were fed with a nutrient solution containing one of two phosphorus (P) levels, 32µM (I P) or 96µM (II P), to test the consequence of enhanced P nutrition by the AM fungus on disease dynamics. Mycorrhizal plants had a similar development to that of control plants. Treatment withPhytophthora nicotianae var.parasitica resulted in a visible reduction in plant weight and in a widespread root necrosis in plants without mycorrhiza. The presence of the AM fungus decreased both weight reduction and root necrosis. The percentage reduction of adventitious root necrosis and of necrotic root apices ranged between 63 and 89% The enhancement of P nutrition increased plant development, but did not appreciably decrease disease spread. In our system, mycorrhiza increased plant resistance toP. nicotianae var.parasitica infection. Although a contribution of P nutrition by mycorrhiza cannot be excluded, other mechanisms appear to play a crucial role.

Phosphorus responses of C3and C4species

An hypothesis was formulated that phosphorus (P) partitioning in tissues of C 4 leaves would permit C 4 plants to resist P deficiency better than C 3 plants. To test this hypothesis, 12 C 3 , C 4 , and C 3 -C 4 intermediate species were grown at adequate, deficient, and severely deficient P supply in a solid-phase-buffered sand culture system to characterize photosynthetic and growth responses. Species differed considerably in response to P stress. The growth of C 3 species was more sensitive to P supply than C 4 species, but C 3 and C 4 species had similar photosynthetic P use efficiency, and C 4 species did not have low leaf P content, contrary to our hypothesis. In fact, leaf photosynthetic rates were not correlated with growth responses. Moncots had lower leaf P content and better maintenance of leaf production under P stress than dicots, because of greater inhibition of branching (dicots) than of tillering (monocots). The most P efficient species in this survey was Brachiaria, a C 4 monocot that increased root biomass allocation under stress while maintaining P allocation to the shoot. It is concluded that C 4 species are not inherently more P efficient than C 3 species, but that monocots are more P efficient than dicots, because of contrasting P and biomass allocation under stress.

490 PB 140 MARIGOLD GROWTH IN SOILLESS MEDIA AMENDED WITH PHOSPHORUS-CHARGED ALUMINA

Soilless growing media are used extensively in the greenhouse, especially for the potted plant production. Unlike soil having a phosphorus (P)-fixing ability, soilless media allows greater P leaching from the media. Leaching of excess P results in inefficient fertilizer utilization and effluent pollution. In hydroponic and sand-culture systems, alumina adsorbed with P (P-alumina) has been developed as a P source to maintain buffered P concentrations in nutrient solutions. This P-alumina has not been used with soilless media; however, it may have a potential of serving as a P source for plant growth and a P buffer to alleviate P leaching in soilless media. Marigolds were grown in soilless media (peat moss: vermiculite: sand=2:2:1, v/v/v) with P-alumina at various concentrations being substituted for sand. These marigolds were fertilized with a nutrient solution containing no additional P, while the control was fertilized with complete nutrient solution. In four cultivars of marigolds, me P-alumina treatments produced comparable or superior growth and floral production compared to plants provided with complete nutrient solutions or conventional fertilizer. 70% of applied P was leached in conventional treatments compared to only 2% in the P-alumina treatments.

The Influence of Terbufos on Primisulfuron Absorption and Fate in Corn (Zea mays)

Terbufos and primisulfuron interactions were evaluated under growth chamber conditions using a sand culture system. Terbufos was applied to transplanted corn seedlings, followed in 5 d by foliar applications of primisulfuron plus nonionic surfactant. Primisulfuron and terbufos alone did not cause corn injury; however, shoot dry weight and shoot length were reduced 28 and 36% in terbufos treatments 96 h after primisulfuron application. Primisulfuron absorption and translocation were not affected by terbufos, but the half-life of primisulfuron increased from 2 to 3.5 h in terbufos treatments. Terbufos did not affect primisulfuron metabolite profiles. The basis for increased primisulfuron phytotoxicity in terbufos treatments appeared to result from reduced primisulfuron metabolism.

The effect of Paxillus involutus Fr. on aluminum sensitivity of Norway spruce seedlings.

Non-mycorrhizal Norway spruce seedlings (Picea abies Karst.) and Norway spruce seedlings colonized with Paxillus involutus Fr. were grown in an axenic silica sand culture system. After successful mycorrhizal colonization, the seedlings were exposed to 200 or 800 micro M AlCl(3) for 10 weeks. In both non-mycorrhizal and mycorrhizal seedlings, exposure to Al significantly reduced root growth and the uptake of Mg and Ca. After 5 weeks of exposure to 800 micro M Al, the mycorrhizal seedlings had significantly higher chlorophyll concentrations than the non-mycorrhizal seedlings, although no difference in Mg nutrition was apparent. After 10 weeks of exposure to Al, both non-mycorrhizal and mycorrhizal seedlings exhibited needle chlorosis and reduced photosynthetic activity. However, the aluminum-induced reduction in shoot growth was largely ameliorated by colonization with P. involutus. We conclude that mycorrhizal colonization modifies the phytotoxic effects of Al in Norway spruce seedlings. However, differences in physiological responses to Al between mycorrhizal and non-mycorrhizal seedlings may be largely reduced in the long term as a result of impaired mineral nutrient uptake.

Contamination of Ammonium-Based Nutrient Solutions by Nitrifying Organisms and the Conversion of Ammonium to Nitrate.

Conversion of ammonium to nitrate and contamination by nitrifying organisms are often assumed not to be significant in ammonium-based nutrient solutions. To assess this assumption, maize (Zea mays) and pea (Pisum sativum) were grown under greenhouse conditions in aeroponic, hydroponic, and sand-culture systems containing 2 mM ammonium chloride as the sole nitrogen source and evaluated for the activity of contaminating nitrifying organisms. In all three culture systems, root colonization by nitrifying organisms was detected within 5 d, and nitrate was detected in the nutrient solution within 10 d after seedling transfer. In sand culture, solution nitrate concentration reached 0.35 mM by the end of the 17-d experiment. Consistent with the microbial ammonium oxidation sequence, nitrite was detected earlier than nitrate and remained at lower levels throughout the experiment. Nitrate was found in significant quantities in root and shoot tissues from seedlings grown in ammonium-based nutrient solutions in all of the solution culture systems. Maize seedlings grown in an ammonium-based hydroponic system contained nitrate concentrations at 40% of that found in plants grown in nitrate-based solution. Determination of nitrate (or nitrite) levels in the nutrient solution was the weakest indicator of the activity of nitrifying organisms. A bioassay for the presence of nitrifying organisms in combination with tissue analysis for nitrate was a better indicator of microbial conversion of ammonium to nitrate in nutrient solution culture. The results have implications for the use of ammonium-based nutrient solutions to obtain plants suitable for research on induction of nitrate uptake and reduction or for research using solution culture to compare ammonium versus nitrate fertilization.

Genotipic responses of olive plants to sodium chloride

Abstract The effect of NaCl‐salinity on growth responses and tissue mineral content was investigated for two olive (Olea europaea L.) genotypes of different vigor, Leccino and Frantoio. Forty‐day‐old self‐rooted plants were grown for a 60‐day period in a sand culture system supplied with a 1/2 strength Hoagland solution with the addition of 0,12.5,25,50, and 100 mM NaCl. Plants were harvested at 12‐day intervals, and the dry weights of shoot, and principal and lateral roots were evaluated. Relative growth rate (RGR) was also estimated. At the same time, plant tissues were analysed for N, P, K, Ca, Mg, Na, and Cl content. Growth inhibition by NaCl treatments was greater for Leccino than Frantoio plants. At the end of the experiment, 50 mM NaCl significantly reduced Leccino growth, while negative effects on Frantoio were detected only when using 100 mM NaCl. Leccino always accumulated more Na and Cl in the leaves than Frantoio. In a similar manner, Na/K ratio was always higher in the Leccino leaves compared...

The effect of aluminium on uptake and distribution of magnesium and calcium in roots of mycorrhizal Norway spruce seedlings

Spruce seedlings (Picea abies (L.) Karst.) colonized with Lactarius rufus (Scop.) Fr. or Lactarius theiogalus Fr. were grown in an axenic silica sand culture system with frequently renewed nutrient solution. After successful mycorrhizal colonization the seedlings were exposed to 800 μM Al(NO3)3 (pH 3.9) for 13 or 17 weeks. Concentrations of Al, Mg, and Ca in the tissues of the mycorrhizal root tips were determined by X‐ray microanalysis. After 13 or 17 weeks of exposure to Al, high Al concentrations were found in cell walls of all mycorrhizal tissues except the stele tissues. Compared to the controls Mg levels in most of the mycorrhizal structures were reduced by Al treatment. Calcium levels in cortex cell walls of root tips colonized with L. rufus were reduced by exposure to Al. However, in cell walls of the stele Ca levels were significantly increased. No differences in Al or Mg levels were detected in structures of mycorrhizal and non‐mycorrhizal root tips from the same individual seedlings. These results suggest that (1) the endodermis is the primary barrier to radial Al transport and (2) the presence of a hyphal sheath did not prevent Al from reaching the root cortex and from displacing Mg and Ca.

Comparative Salinity Responses among Pigeonpea Genotypes and Their Wild Relatives

Soil salinity can be a major constraint to pigeonpea (Cajanus cajan (L.) Millsp.) in the regions where it is predominantly grown. This study was conducted to assess the extent of genetic variation for salinity tolerance in the germplasm of pigeonpea and its wild relatives. Solution culture experiments in a greenhouse and controlled environment chamber were conducted to screen a range of cultivated pigeonpea genotypes for ability to germinate and grow up to 60 d under saline conditions. Several wild relatives of pigeonpea were screened for salinity response in a sand culture system in a greenhouse. Among cultivated pigeonpea genotypes, ICPL 227 was one of the most tolerant and HY 3C one of the most sensitive genotypes tested. None of the pigeonpea genotypes tested were able to survive beyond 30 d at 8 dS m−1 or higher salinity levels. The extent of variation in salinity response among cultivated pigeonpea genotypes appeared too limited to warrant genetic enhancement of salinity tolerance. Among the wild relatives of pigeonpea, various species of Atylosia, Rynchosia, and Dunbaria showed a wide range of variation in their salinity tolerance (critical levels from 4 to 12 dS m−1): A. albicans (W. & A.) Benth., and A. platycarpa could grow in a sand culture system at 12 dS m−1 and Rynchosia albiflora could not tolerate salinity levels above 4 dS m−1. These results suggest that using wild relatives for genetic improvement may increase salinity tolerance of pigeonpea.

Culture of mycorrhizal tree seedlings under controlled conditions: Effects of nitrogen and aluminium

A sand culture system was developed for growth of mycorrhizal seedlings under monoxenic conditions, with frequently renewed nutrient solution The composition of the nutrient solution resembled that of a forest soil solution, based on long‐term measurements from forest sites at Soiling, northern Germany. Seedlings of Picea abies (L.) Karst. inoculated with Lactarius rufus (Scop.) Fr. were grown in this culture system. Plants developed rapidly, having almost totally mycorrhizal root systems. Nitrate at 2.7 mM in the nutrient solution and applied over a 13 week period had no negative effect on mycorrhizal development. Ammonium at 2.7 mM reduced the degree of mycorrhizal infection slightly, in such a way that the degree of mycorrhizal infection was reduced to a much less extent than the total number of root lips. Hence, the impact of NH+4 may be primarily on root development and not on mycorrhizal fungal colonization. When the concentrations of NO‐3 and NH+4 used in the present study are compared to those found in forest soil solutions, NO‐3 and NH4+ would not appear to influence mycorrhizal development negatively under natural conditions. Aluminium at 0.8 mM and applied over a 13 week period reduced Mg uptake into roots and needles by 52 and 64%, respectively, resulting in needle chlorosis and strongly reduced photosynthetic activity. From a comparison of this study with others, no major difference in physiological response to aluminium exposure between non‐mycorrhizal seedlings and seedlings colonized with Lactarius rufus was found.

Distribution of lead in mycorrhizal and non‐mycorrhizal Norway spruce seedlings

Non‐mycorrhizal spruce seedlings(Picea abies Karst.) and spruce seedlings colonized with Lactarius rufus (Scop.) Fr. or two strains of Paxillits involutus (Batsch) Fr. were grown in an axenic silica sand culture system with frequently renewed nutrient solution. After successful mycorrhizal colonization, the seedlings were exposed to 1 μM PbCI2 for 19 weeks. The degree of infection in all of the mycorrhizal treatments approached 100% during the experiment and was not affected by exposure to Pb. However, the number of root tips per root dry weight and the shoot: root ratio, both in the non‐mycorrhizal and the mycorrhizal seedlings, had decreased after the 19 week treatment with PbCl2 Using X‐ray microanalysis, the distribution and concentration of Pb in the tissues of mycorrhizal and non‐mycorrhizal root tips were compared. In the mycorrhizae of seedlings exposed to Pb no significant accumulation of Pb in the hyphal mantle or in fungal cell walls of the Hartig net were detected. Lead accumulated primarily in the cortex cell walls both of non‐mycorrhizal and mycorrhizal root tips. No significant difference of Pb concentrations in root cortex cell walls of non‐mycorrhizal and mycorrhizal seedlings was found; except for seedlings colonized with Paxillus involutus strain 537. However, at the endodermis no effect of mycorrhizal fungal colonization on the Pb tissue concentration was detected. The presence of the fungal sheath did not prevent Pb from reaching the root cortex. The endodermis acted as a barrier to Pb radial transport in both mycorrhizal and non‐mycorrhizal seedling roots.

OSMOREGULATION IN YOUNG JOJOBA SEEDLINGS

The possibility of osmotic adjustment to salinity in Jojoba was studied in a sand culture system. After being stablished, 2 WKs old seedlings were exposed to 1/2 strength hoagland's solution plus NaCl salt to make up -0.7., -0.4, -0.6, -0.8, & -1 MPa. Shoot & leaf elongation, components of Ψleaf, proline accumulation, & inorganic salts were determined every 24 hour for 9 days. Shoot & leaf length were reduced at -0.8 and -0.4 MPa respectively. Osmotic adjustment occured only above -0.8 MPa at the rate of 0.21 If MPa/day. Total inorganic salts in whole plant increased with a decrease in solution Ψw. However, above -0.8 MPa excess Na & Cl ions were excluded from the leaves & accumulated within the roots, while K/Na ratio remained higher above -1 MPa. The selective uptake of K ions seems a possible mechanism for osmotic adjustment in Jojoba. Accumulation of Na & Cl ions under -1 MPa correlated with occasional pale green discoloration & tip-burn of leaves. Although the accumulation of proline was considerable at & below -0.8 MPa, but did not play a significant role in osmoregulation.

An automated greenhouse sand culture system suitable for studies of P nutrition

Abstract. Maintenance of realistically low solution P concentrations under controlled conditions is a major difficulty in studies of P nutrition. In this report, we describe a relatively simple and economical sand culture system capable of sustaining plant growth to maturity under controlled yet realistic P regimes. The system uses Al2O3 as a solid‐phase P buffer, and modern process control technology to control irrigation and addition of other mineral nutrients. Aspects of the design, use and potential applications of automated solid‐phase systems are discussed. The system was used to grow Phaseolus vulgaris to matarity at 0.4 mmol m3, 1.0 mmol m3 and 27 mmol m3 P with and without mycorrhizal inoculation. At flowering, low solution P concentrations were associated with reduced leaf concentrations of P in nonmycorrhizal plants, and reduced leaf concentrations of Ca in both mycorrhizal and nonmycorrhizal plants. Mycorrhizal inoculation increased leaf P, K, Mg and Mn concentrations, but reduced leaf N concentration. Low P regimes reduced final seed yield by diminishing both the number of pods per plant and the number of seeds per pod. Mycorrhizal inoculation significantly enhanced seed yield under low P regimes by increasing seed weight, the number of pods per plant, and the number of seeds per pod.

Salinity Tolerance in F1 Hybrids of Pigeonpea and a Tolerant Wild Relative

Salinity in soil or water presents a stress condition to crop plants that is of increasing importance in the sustainability and stability of crop production in the semiarid regions of the world. This study determined the potential for genetic introgression of salinity tolerance from a wild relative, Atylosia albicans (W. & A.) Benth., to cultivated pigeonpea, Cajanus cajan (L.) Millse. A sand culture system was used to grow the salt‐tolerant A. albicans, salt‐sensitive C. cajan, and their F1 hybrids at various precisely maintained salinity levels. The results demonstrated the feasibility of transferring salinity tolerance from A. albicans to C. cajan. The high level of salinity tolerance in A. albicans was expressed as a dominant genetic factor in both the reciprocal F1 hybrids of this species and C. cajan. The physiological attributes conferring salinity tolerance in A. albicans and the F1 hybrids include Na and Cl retention in the roots and limited translocation to the shoots, high K selectivity, and maintenance of transpiration rate under saline conditions.

Effects of ammonium and nitrate on mycorrhizal infection of Norway spruce seedlings under controlled conditions

Seedlings of Picea abies inoculated with Lactarius rufus or L. theiogalus were grown in a sterile sand culture system with flowing nutrient solution. NO 3 − at 2.7 mM applied over a 90 or 120 days period had no significant effect on the degree of infection and total numbers of mycorrhizae per seedling, whereas NH 4 + at 1.5 mM or 2.7 mM had a significant negative effect on mycorrhizal development.

Effect of seed weight, and seed phosphorus and nitrogen concentrations on the early growth of wheat seedlings

Wheat seeds of uniform weight selected from 3 batches of seed with phosphorus (P) concentrations of 0.14, 0.17 and 0.19% were sown in soil with a range of applied P treatments. Seedling emergence was more rapid the higher the seed P. By 25 days after sowing all plants grown at the highest concentration of applied P were similar in size, but with lower applied P, plants from seed with higher P concentrations had an advantage. A range of weight classes was selected from 2 batches of seed raised at low or high concentrations of P. There were 11 groups ranging in mean seed weight from 28 to 58 mg and in seed P from 0.13 to 0.37%. Seedlings from the high P batch had larger first leaves, a higher dry weight, and longer roots than those from the low P batch when grown in a highly P-deficient sand culture system. Within each batch, heavier seeds produced larger leaves, heavier plants and longer roots. The yield differences between batches were largely accounted for if the seed P content (�g P/seed) was considered rather than either percentage P or seed weight alone. Differences in seed nitrogen concentration or content did not consistently account for differences in seedling growth.

Differential response of oats, sweet corn, cauliflower and broccoli to low manganese in a sand culture system

Abstract Oats and sweet corn but not cauliflower and broccoli growth was reduced by a complete‐minus‐Mn nutrient feed compared to a complete nutrient feed in a sand culture system in a greenhouse. Growth of oats and sweet corn were reduced to such an extent within 43 days of seeding that treatments on these two crops were terminated. Growth of cauliflower and broccoli were continued to 90 days and no effects were noted by withholding Mn in the nutrient feed. Chemical analyses of the dried plant material showed that cauliflower and broccoli Mn concentrations were considerably lower in the minus‐Mn compared to the complete nutrient treatment. Cauliflower and broccoli were apparently able to extract Mn from the sand culture system. Oats and corn apparently did not extract adequate Mn for proper growth from the minus‐Mn system. The lack of Mn in the nutrient treatment influenced the P, K, Mg, B and Cu concentrations in and/or uptake by cauliflower and broccoli but Ca, Fe and Zn were not affected.

Relative Aluminum Tolerance of Prunus Rootstocks

Abstract A sand culture system was used to compare growth reduction in Prunus rootstocks due to high A1 concentration. Aluminum at 50 mg liter-1 nutrient solution resulted in A1 tissue levels of 288 to 408 mg.kg-1, shoot growth reduction of 41% to 77%, and root growth reduction of 9% to 86%. Based on relative growth reduction, Prunus tomentosa Thunb. was more sensitive to A1 toxicity than were Nemaguard, Nemared, ‘Lovell’ [P. persica (L.) Batsch], P. besseyi Bailey, P. cerasifera Ehrh., and P. insititia L. Nemaguard and P. tomentosa had higher shoot A1 concentration at 50 mg Al/liter than the other rootstocks tested.