Lactuca Sativa Cv Research Articles

Role of manganese in low-pH-induced root hair formation in Lactuca sativa cv. Grand Rapids seedlings.

Root hair formation is induced by low pH in lettuce ( Lactuca sativa L. cv. Grand Rapids) seedlings cultured in mineral medium. The role of mineral concentrations in this phenomenon was investigated, especially for manganese. When lettuce seedlings were cultured in media that were deficient in calcium (Ca), manganese (Mn), boron (B) or molybdenum (Mo), morphological changes were induced in roots. Deficiency of other nutrients had little effect on root hair formation. Ca or B deficiency inhibited the growth of the main root and the formation of root hairs, regardless of pH. Mn or Mo deficiency increased root hair formation at pH 6 and suppressed main root growth slightly. In contrast, increasing the Mn concentration suppressed low-pH-induced root hair formation. The Mn content of roots grown at pH 4 was only about 15% of that at pH 6. In contrast, the Mo content of roots grown at low pH was about six times that of roots grown at neutral pH. These results suggest that root hair formation induced by low pH is at least partly mediated by decreased Mn uptake in root cells.

Evapotranspiração da alface em função de água e nitrogênio

The purpose of this work was to evaluate the evapotranspiration of lettuce ( Lactuca sativa ) cv “Veronica” to water and nitrogen levels. The experiment was conducted on the greenhouse of Centro Tecnico de Irrigacao , at Universidade Estadual de Maringa campus (state of Parana, South of Brazil), from March 16 to April 25, 2001. It was conducted in a 4 x 4 factorial scheme, with 16 treatments. The experimental design was completely randomized with four levels of water (W 1 = 62.5; W 2 = 75.0; W 3 = 87.5 and W 4 = 100% of the water retention capacity of the soil) and four levels of nitrogen (N 1 = 75; N 2 = 150; N 3 = 225 and N 4 = 300mg dm 3 ) subdivided in five identical applications during the studied period in the plant cycle. Experimental unity was a vase with 2kg of soil and one plant of lettuce. The replacement of water occurred when the mass of water evapotranspiration of each treatment reached 50% of the water retention capacity. Within the greenhouse was also measured the evaporation by a pan (evaporimeter) with 60cm diameter and 25cm height. The lettuce evapotranspiration was influenced by water and nitrogen treatment. Lettuce evapotranspiration was linearly affected by nitrogen and quadratic affected by water levels. If soil water is no limiting, lettuce evapotranspiration decreases when nitrogen level increases.

Produção de alface em função de água e de nitrogênio

The purpose of this work was to evaluate the production of lettuce Lactuca sativa cv. Verônica to water and nitrogen levels. The experiment was conducted on the greenhouse of Centro Técnico de Irrigação, at Universidade Estadual de Maringá campus (State of Paraná, South of Brazil), from March 16 to April 25, 2001. It was conducted in a 4 x 4 factorial scheme, with 16 treatments. The experimental design was completely randomized with four levels of water (W1 = 62.5; W2 = 75.0; W3 = 87.5 and W4 = 100% of the water retention capacity of the soil) and four levels of nitrogen (N1 = 75; N2 = 150; N3 = 225 and N4 = 300mg N/dm3) subdivided in five identical applications during the studied period in the plant cycle. Every experimental unity was compound of one vase with 2kg of soil and one plant of lettuce. The replacement of water occurred when the mass of water evapotranspiration of each treatment reached 50% of the water retention capacity of the soil. The lettuce production was linearly affected by nitrogen and quadratic affected by water levels. Water and nitrogen are substituting production factors to lettuce, then increasing any of factors on soil, the other can be reduced without changing the production.

Cadmium uptake and subcellular distribution in plants of Lactuca sp. Cd–Mn interaction

Cd uptake and subcellular distribution in ( Lactuca sativa cv. Grandes Lagos) was studied. In vivo and in vitro experiments were carried out to study Cd effect on Mn uptake and subcellular distribution. Lettuce plants were grown in hydroponics with nutrient solutions containing 0.1 and 1.0 mg Cd l −1 in a greenhouse (in vivo experiments). Also, Cd was directly infiltrated on lettuce leaves in in vitro studies (0.5 and 1 mg Cd l −1), to minimize absorption and transport processes. Root and shoots were sampled after 16 days of exposure to the Cd solutions. Cd, Mn and other micronutrients were assessed in the different parts of the plant sampled and in the subcellular fractions obtained after wet mineralization, using A.A. spectrophotometry. Results show that Cd was accumulated in leaves mainly in cell wall fraction (64%) and this accumulation was fairly independent of Cd level in nutrient solution. The lowest Cd concentration (12–14%) was found in chloroplasts for both Cd levels tested. The increase in Cd concentration in the external medium caused an increase in Mn uptake and translocation to the shoots of lettuce plants, in contrast to the behavior of the other essential micronutrients, and an increase in Mn content in the chloroplasts, suggesting an interaction between Cd and Mn at the chloroplast level.

PREDICTIVE NEURAL NETWORK MODELING OF pH AND ELECTRICAL CONDUCTIVITY IN DEEP–TROUGH HYDROPONICS

A model is presented that predicts pH and electrical conductivity (EC) changes in the root zone of lettuce (Lactucasativa cv. Vivaldi) grown in a deeptrough hydroponic system. A feedforward neural network is the basis of that modeling.The neural network model has nine inputs (pH, EC, nutrient solution temperature, air temperature, relative humidity, lightintensity, plant age, amount of added acid, and amount of added base) and two outputs (pH and EC at the next time step).The most suitable and accurate combination of network architecture and training method was one hidden layer with ninehidden nodes, trained with the quasiNewton backpropagation algorithm. The model proved capable of predicting pH at thenext 20minute time step within 0.01 pH units and EC within 5 .Scm1. Simpler prediction methods, such as linearextrapolation and the lazy man prediction (in which prediction is the value of the previous time step), gave comparableaccuracy much of the time. However, they performed poorly in situations where the control actions of the system had beenactivated and produced relatively rapid changes in the predicted parameters. In those cases, the neural network model didnot encounter any difficulties predicting the rapid changes. Thus, the developed model successfully identified dynamicprocesses in the root zone of the hydroponic system and accurately predicted onestepahead values of pH and EC.

Production of dwarf lettuce by overexpressing a pumpkin gibberellin 20-oxidase gene.

We investigated the effect of overexpressing a pumpkin gibberellin (GA) 20-oxidase gene encoding an enzyme that forms predominantly biologically inactive products on GA biosynthesis and plant morphology in transgenic lettuce (Lactuca sativa cv Vanguard) plants. Lettuce was transformed with the pumpkin GA 20-oxidase gene downstream of a strong constitutive promoter cassette (El2-35S-Omega). The transgenic plants in which the pumpkin gene was detected by polymerase chain reaction were dwarfed in the T(2) generation, whereas transformants with a normal growth phenotype did not contain the transgene. The result of Southern-blot analysis showed that the transgene was integrated as a single copy; the plants segregated three dwarfs to one normal in the T(2) generation, indicating that the transgene was stable and dominant. The endogenous levels of GA(1) and GA(4) were reduced in the dwarfs, whereas large amounts of GA(17) and GA(25), which are inactive products of the pumpkin GA 20-oxidase, accumulated in these lines. These results indicate that a functional pumpkin GA 20-oxidase is expressed in the transgenic lettuce, resulting in a diversion of the normal pathway of GA biosynthesis to inactive products. Furthermore, this technique may be useful for controlling plant stature in other agricultural and horticultural species.

608 Super-elevated CO2 Concentrations Reduce Growth of Radish and Lettuce

Radish (Raphanus sativus cv. Giant White Globe) and lettuce (Lactuca sativa cv. Waldmann's Green) plants were grown for 25 days in growth chambers at 23 °C, ≈300 μmol·m-2·s-1 PPF, and 18/6 photoperiod, and four CO2 concentrations: 400, 1000, 5000, and 10,000 μmol·mol-1. Average total dry mass (g/plant) at the 400, 1000, 5000 and 10,000 μmol·mol-1 treatments were 6.4, 7.2, 5.9, and 5.0 for radish and 4.2, 6.2, 6.6, and 4.0 for lettuce. Each species showed an expected increase in yield as CO2 was elevated from 400 to 1000 μmol·mol-1, but super-elevating the CO2 to 10,000 μmol·mol-1 resulted in suboptimal growth. In addition, many radish leaves showed necrotic lesions at 10,000 μmol·mol-1 by 17 days and at 5000 μmol·mol-1 by 20 days. These results are consistent with preliminary tests in which radish cvs. Cherry Belle, Giant White Globe, and Early Scarlet Globe were grown for 16 days at 400, 1000, 5000, and 10,000 μmol·mol-1. In that study, `Giant White Globe' produced the greatest total dry mass at 1000 (3.0 g/plant) and 5000 μmol·mol-1 (3.0 g/plant), and the least at 10,000 μmol·mol-1 (2.2 g/plant). `Early Scarlet Globe' followed a similar trend, but `Cherry Belle' showed little difference among CO2 treatments. Results suggest that super-elevated CO2 can depress growth of some species, and that sensitivities can vary among genotypes.

First Report of Bacterial Leaf Spot of Basil Caused by Pseudomonas viridiflava in Argentina.

In June 1998, during a cool, humid period, typical bacterial spot symptoms were observed on basil plantlets (Ocimun basilicum L. 'Royal Louis' and 'Zaes') in a commercial greenhouse in La Plata, Argentina. Affected plants had dark brown to black lesions on cotyledons. Spots on leaves were first water soaked, then became necrotic and progressed inward from the margins. Disease incidence approached 30%. Symptoms were similar to those reported by Little et al. (2) on basil affected by Pseudomonas viridiflava. No pathogenic fungi or viruses were associated with symptomatic plants. Bacterial streaming was observed from lesion margins. Bacteria consistently isolated from leaf lesions formed cream-colored, glistening, convex colonies on sucrose peptone agar and a green fluorescent pigment on King's medium B. Bacterial growth produced a distinctive olive green pigment on glycerol agar medium and a pink pigment on T-5 medium (1). Four isolates selected for further study were aerobic, Gram-negative, non-spore-forming rods. In LOPAT (levan-oxidase-potato rot-arginine dihydrolase-tobacco hypersensitivity) tests, all induced a hypersensitive response in tobacco plants, caused soft rot of potato tubers, and were negative for levan, oxidase, and arginine dihydrolase. In addition, strains rotted onion slices and produced a reddish sunken lesion on bean pods. Acid was produced aerobically from D-glucose, mannitol, mesoinositol and sorbitol, but not from D-arabinose, L-rhamnose, melibiose, amygdalin, or sucrose. Bacteria used D-tartrate, pyruvate, and citrate, but not benzoate. The strains did not hydrolyze starch, exhibited an oxidative metabolism of glucose, and did not reduce nitrates to nitrites or accumulate poly-β-hydroxybutyrate inclusions. Negative reactions were obtained with indole, ornithine, and D-tryptophan. Isolates hydrolyzed gelatine, used Tween 80, were positive for catalase, and were unable to grow in the presence of 5% NaCl. Colonies developed at 4°C but not 37°C. Reactions were identical to those of reference strains ICMP 5776 and 12363, which were included in all tests for comparison. Pathogenicity was verified on 35-day-old basil plants by both spraying and infiltration inoculations with bacterial suspensions (108 and 105 cells per ml, respectively). Carborundum was included in the inoculum used for a set of plants inoculated by spraying. Controls were injected or sprayed (with and without Carborundum) with sterile, distilled water. In addition, bean (Phaseolus vulgaris cv. Nag12 INTA) and lettuce (Lactuca sativa cv. criolla), both reported as host plants, were inoculated by spraying with bacterial suspensions of 107 cells per ml plus Carborundum. After 48 h in a humid chamber, inoculated plants and controls were maintained at 23 ± 3°C. Symptoms on basil plants inoculated by injection or spraying with Carborundum were identical to those observed on basil in the field. Symptoms on bean and lettuce were similar to those described for P. viridiflava. The bacterium was reisolated from lesions of all species tested, fulfilling Koch's postulates. No lesions were observed on controls or on plants sprayed without Carborundum, suggesting that bacteria gain entry through wounds. The microorganism was identified by physiological tests and polymerase chain reaction as P. viridiflava. This is the first report of bacterial leaf spot of basil in Argentina.

Expression of the Bar Gene Confers Herbicide Resistance in Transgenic Lettuce

Resistance to bialaphos, a broad-spectrum herbicide, was introduced into Lactuca sativa cv. Evola by Agrobacterium tumefaciens-mediated transformation. A. tumefaciens strains 0310 and 1310, both carrying the bialaphos resistance (bar) and neomycin phosphotransferase (nptII) genes, were used for transformation. Primary transformants were selected on kanamycin sulphate-supplemented shoot regeneration medium. Integration of both transgenes was confirmed by non-radioactive Southern hybridisation. The hypervirulent plasmid ToK47 in A. tumefaciens strain 1310 generated multiple insertions of T-DNA in some transgenic plants; the absence of pToK47 (strain 0310) resulted in single gene inserts in all plants tested. Resistance to glufosinate ammonium was observed in axenic seedlings grown on medium supplemented with the herbicide at 5 mg l−1 and in glasshouse-grown plants sprayed with the compound at 300 mg l−1. Stable expression of the bar gene was observed in R2 generation plants. The kanamycin resistance of R1 seedlings was observed by germinating seeds on medium supplemented with 200 mg l−1 kanamycin sulphate. The presence of NPTII protein and PAT enzyme activity were demonstrated by ELISA and PAT enzyme assay respectively. Transgenes segregated in a Mendelian fashion in some plant lines in the R1 generation; herbicide resistance also segregated in the expected ratio in the R2 generation in most transgenic lines. This study confirmed that an agronomically important transgene can be integrated and stably expressed over several generations in lettuce.

Blue light control of hypocotyl elongation in etiolated seedlings of Lactuca sativa (L.) cv. Grand Rapids related to exogenous growth regulators and endogenous IAA, GA3 and abscisic acid

Results of studies on the interaction of blue light (B) and exogenous applied plant hormones (IAA, GA3 and ABA) as well as inhibitors of their synthesis on the control of hypocotyl elongation in etiolated seedlings of Lactuca sativa (L.) cv. Grand Rapids are presented, and compared with endogenous GA3, IAA and ABA levels measured by capillary gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). Hypocotyl elongation of etiolated seedlings was linearly inhibited by increasing the B fluence rate between 0 and 18.3 μmol m−2 s−1. Both GA3 and IAA added to the incubation medium at different concentrations were able to eliminate partially the inhibition of growth caused by 7.2 μmol m−2 s−1 B. When dark (D)-grown seedlings were treated with Ca-prohexadione, a specific inhibitor of gibberellin 3β-hydroxylation, they showed a growth inhibition similar to under B. Also, a suppression of growth as in B was obtained when D-grown seedlings were treated with ABA 380 μM. By lowering ABA levels with fluridone (an inhibitor of ABA synthesis) a partial reversion of hypocotyl growth inhibition was obtained in B-grown seedlings. While none of the growth promoters used were able to reverse completely the growth inhibition caused by B, a proper combination of GA3, IAA and (eventually) fluridone, abolished the B effects. Correspondingly, lower levels of GA3 and IAA and a higher concentration of ABA were measured by GC-MS-SIM in B-grown hypocotyls than in D-grown ones. These results support the hypothesis that hormones are implicated in mediation of B light-dependent inhibition of hypocotyl elongation, which seems to be the result of a balance among endogenous levels of growth promoting and growth inhibiting hormones.

Linking plant tissue concentrations and soil copper pools in urban contaminated soils

Copper tissue concentrations of radish ( Raphanus sativa cv. Cherry Belle), lettuce ( Lactuca sativa cv. Buttercrunch) and ryegrass ( Lolium perenne cv. Barmultra) grown in a greenhouse in urban contaminated soils are compared to total, soluble and free ion copper pools. The tissue concentrations of copper vary between 8.1 and 82.6 mg Cu kg −1 dry tissue and the total soil copper content varies between 32 and 640 mg Cu kg −1 dry soil. The linear regressions with cupric ion activity and total soil copper are both significant (p < 0.01), but cupric ion activity yields a higher level of statistical significance in every case. The results support the hypothesis that free metal in the soil solution is a better indicator of plant metal bioavailability than either total or soluble metal.

Effect of crop development on biogenic emissions from plant populations grown in closed plant growth chambers

The Biomass Production Chamber at John F. Kennedy Space Center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. The head space atmosphere of a 26-day-old lettuce ( Lactuca sativa cv. Waldmann's Green) stand was repeatedly sampled and emissions identified and quantified using GC-mass spectrometry. Concentrations of dimethyl sulphide, carbon disulphide, α-pinene, furan and 2-methylfuran were not significantly different throughout the day; whereas, isoprene showed significant differences in concentration between samples collected in light and dark periods. Volatile organic compounds from the atmosphere of wheat ( Triticum aestivum cv. Yecora Rojo) were analysed and quantified from planting to maturity. Volatile plant-derived compounds included 1-butanol, 2-ethyl-1-hexanol, nonanal, benzaldehyde, tetramethylurea, tetramethylthiourea, 2-methylfuran and 3-methylfuran. Concentrations of volatiles were determined during seedling establishment, vegetative growth, anthesis, grain fill and senescence and found to vary depending on the developmental stage. Atmospheric concentrations of benzadehyde and nonanal were highest during anthesis, 2-methylfuran and 3-methylfuran concentrations were greatest during grain fill, and the concentration of the tetramethylurea peaked during senescence.

104 HORTICULTURAL USES FOR SEWAGE SLUDGE COMPOST

Compost made from sewage sludge (40% by volume) and chipped trimmings of Eucalyptus trees (60%) was evaluated as a soil amendment for the field. production of onion (Allium cepa cv. Spanish Sweet Utah), lettuce (Lactuca sativa cv. Black Seeded Simpson), snapdragon (Antirrhinum majus cv. Sonnet Yellow), and turfgrass (Festuca arundinacea cv. Marathon). Turf shows a strong reponse to preplant compost applications and is relatively tolerant of the buildup of soluble salts that can occur with compost applications. Also since it is not a food crop the possible uptake of heavy metals is not a major concern. These results indicate the amending of soil for the planting of turf is a likely commercial use of the compost. The authors are presently evaluating the use of the compost as a top dressing on turf plantings.

A Lactuca universal hybridizer, and its use in creation of fertile interspecific somatic hybrids.

A Lactuca sativa cv. Ardente line heterozygous for a gene encoding resistance to kanamycin, a positive and dominant trait, was crossed with cv. Girelle, which is heterozygous for a recessive albinism marker. The resulting seeds yielded 25% albino seedlings, of which 50% were also resistant to kanamycin. Such plantlets (KR, a) grown in vitro were used for preparation of universal hybridizer protoplasts, since green buds that can develop on kanamycin containing-medium should result from fusion with any wild-type protoplast. To test the practicability of this selection scheme, we fused L. sativa KR, a protoplasts with protoplasts derived from various wild Lactuca as well as various other related species. Protoplast-derived cell colonies were selected for resistance to kanamycin at the regeneration stage. Green buds were regenerated after fusion with protoplasts of L. tatarica and of L. perennis. So far, 9 interspecific hybrid plants have been characterized morphologically. In addition, random amplified polymorphic DNA (RAPD) analysis with selected primers confirmed that these plants are indeed interspecific hybrids. Some plants are female-fertile and production of backcross progenies with L. sativa is in progress. Since many desirable traits such as resistances to viruses, bacteria and fungi (Bremia lactucae) have been characterized in wild Lactuca species, the use of somatic hybridization in breeding programmes now appears a practical possibility.

Cumulative effects of sludge compost on crop yields and soil properties

Abstract Onion (Allium cepa cv. Spanish Sweet Utah), lettuce (Lactuca sativa cv. Black Seeded Simpson), snapdragon (Antirrhinum majus cv. Sonnet Yellow), and turfgrass (Festuca arundinacea cv. Marathon) were grown twice annually (spring and fall) on a San Emigdio sandy loam (coarse‐loamy, mixed calcareous thermic, Typic Xerorthents) soil for two years that was treated with a cumulative total of 0, 37, and 74 MT/ha of sewage sludge compost from San Diego. The soil received two compost treatments each year and crops were planted within a week of compost incorporation. Crop growth was monitored and the results of the fourth or final planting are described here. Seedlings of onion, snapdragon and lettuce transplanted to compost treated plots displayed more vigorous establishment than those in the control plots. Compost treatments produced higher yields of onion, turf and lettuce. Snapdragon yield was not affected by compost treatment. Soil analysis of compost treated plots revealed lowered pH and increased levels of organic matter, primary nutrients, soluble salts and heavy metals. A concurrent greenhouse study demonstrated that the presence of chipped Eucalyptus tree trimmings (60% by volume) in the sewage sludge compost did not inhibit the growth of the test crops.

Actions of acid immersion, red light and gibberellin A 3 treatments on germination of thermodormant lettuce seeds

Lactuca sativa cv. Grand Rapids seeds not exposed to dark storage at 30°C (DS) germinated completely at 20°C with red light (R) or 0.5 mM gibberellin A 3 (GA 3) regardless of pretreatment of R, far-red light (FR) or 1-hr acid immersion (pH 0.1) plus water rinse (H +). H + treatment alone increased germination of FR-treated seeds from 16 to 50%. GA 3 had little effect on FR-treated seeds held in DS for between 18 hr and 10 days. Promotion of germination by R decreased slowly with increased DS time and finally disappeared, indicating the induction of thermodormancy. Seeds rendered thermodormant by 10–30-day DS did not germinate with water alone, but germinated 8% or less following R, GA 3 or H + treatment. These thermodormant seeds germinated 85% or more if H + was given before R or GA 3. Thermodormant seeds, which revealed R on days 0, 10 or 20 of DS, germinated 83–90% if given only H + treatment. GA 3 caused higher germination at 20°C in R-pretreated thermodormant seeds than R, indicating synergism between GA 3 and R. The R pretreatment reduced the degree of thermodormancy and also dark reversion of P fr (FR-absorbing form of phytochrome). It is suggested that P fr cannot induce germination in thermodormant seeds although some P fr presists for up to 30 days DS. P fr can function in these thermodormant seeds only when they are given an H + treatment. It is concluded that thermodormant seeds incubated in darkness at 30°C are similar to skotodormant seeds incubated in darkness at 20°C, but the depth of secondary dormancy in the former is deeper. Presumably P fr loss is accelerated at higher temperature.

Sewage Sludge Compost's Cumulative Effects on Crop Growth and Soil Properties

▪ Onion (Allium cepa cv. Spanish Sweet Utah), lettuce (Lactuca sativa cv. Black Seeded Simpson), snapdragon (Antirrhinum majus cv. Sonnet Yellow), and turfgrass (Festuca arundinacea cv. Marathon) were grown twice annually (spring and fall) on a San Emigdio sandy loam (coarse-loamy, mixed calcareous thermic, Typic Xerorthents) soil for two years that was treated with a cumulative total of 0, 37 and 74 MT/ha of sewage sludge compost from San Diego. The soil received two compost treatments each year and crops were planted within a week of compost incorporation. Crop growth was monitored and the results of the fourth or final planting are described here. Seedlings of onion, snapdragon and lettuce transplanted to compost treated plots displayed more vigorous establishment than those in the control plots. Compost treatments produced higher yields of onion, turf and lettuce. Snapdragon yield was not affected by compost treatment. Soil analysis of compost treated plots revealed lowered pH and increased levels of ...

SEWAGE SLUDGE COMPOST'S CUMULATIVE EFFECTS ON CROP GROWTH AND SOIL PROPERTIES

Onion (Allium cepa cv. Spanish Sweet Utah), lettuce (Lactuca sativa cv. Black Seeded Simpson), snapdragon (Antirrhinum majus cv. Sonnet Yellow), and turf (Festuca arundinacea cv. Marathon) were grown twice annually (spring and fall) on a San Emigdio sandy loam (course-loamy, mixed calcareous thermic, Typic Xerorthents) soil for two years that was treated with a cumulative total of 0, 37 and 74 MT/ha of sewage sludge compost from San Diego. The soil received two compost treatments each year and crops were planted within a week of compost incorporation. Crop growth was monitored and the results of the fourth or final planting will be presented. Seedlings of onion, snapdragon and lettuce transplanted to compost treated plots displayed more vigorous establishment than those in the control plots. Compost treatments produced higher yields of onion, turf and lettuce. Snapdragon yield was not affected by compost treatment. Significant changes in pH, CM, EC, and various nutrients were noted upon the analysis of the soil.

ENHANCED SYNTHESIS AND ACCUMULATION OF ACC AND MACC DURING RELIEF OF THERMOINHIBITION WITH KINETIN IN LETTUCE SEED

The level of 1-aminocyclopropane-1-carboxylic acid (ACC) was 0.55 nmol.g-1 in dry lettuce (Lactuca sativa cv. Emperor) seeds. After 4h soak at 25°, 35° and 35°C+ KIN (kinetin, 50μM), the levels were 0, 0.2 and 1.14 nmol.g-1 seeds, respectively. The level of ACC was higher at 35°+KIN than at 35°C for up to 16h soak. No ACC was detectable at 25°C during 2 to 16h soak. In the presence of 50μM ABA, ACC level decreased to 0.2 nmol.g-1 at 4h soak and to zero level during 8 to 16h soak. The level of l-(malonylamino) cyclopropane-1-carboxylic acid (MACC), in dry seeds was 14 nmol.g-1. Exposure to 35°C in the presence or absence of KIN increased the level to 40-42 nmol.g-1 within 2h soaking, while at 25° only a slight increase (23 nmol.g-1) occurred. As in the case of ACC, the level of MACC was higher at 35°C+ KIN than at 35° or 25° for up to 16h soak.When seeds were soaked in ABA, the pattern of MACC produced was similar to that produced at 35°C. The results indicate that ACC synthase activity is enhanced by the addition of KIN at 35°C resulting in increased synthesis and/or accumulation of ACC and MACC. The relationship of ethylene biosynthesis to changes during stress imposition and alleviation by various factors will be discussed.

GROWTH OF LETTUCE IN ANIONIC SURFACTANTS

Anionic surfactants are the major class of surfactants used in detergent, laundry and related industries. Hence, they are a major contaminate of both domestic and industrial waste streams. Lettuce (Lactuca sativa cv Waldemann's Green) was grown in nutrient solutions with the addition of the anionic surfactant, Igepon TC-42. The toxic response of lettuce to Igepon was that the roots turned brown and became necrotic within 24 h following exposure. Growth was supressed for approximately 4 days following exposure to concentration greater than 0.35 mM; new roots formed rapidly and growth resumed. When fresh plants were transferred to the solutions containing Igepon 48 h following introduction of the surfactant no signs of toxicity were observed. This would indicate that either the first series of plants absorbed the toxic material or the Igepon was decayed or degraded in the nutrient solution. The rapid recovery of plants from this stress suggests the potential of a wide range of strategies that could be developed for utilizing waste streams containing anionic surfactants.