Tetcyclacis and Abscisic Acid-Sensitive Reduction of Extracellular Ferricyanide by Mesophyll Cells ofValerianella locustaandLemna gibba
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Abstract:
Electron transport across the plasma membrane of Valerianella locusta mesophyll cells and intact fronds of Lemna gibba, induced by 10−3 M ferricyanide, was inhibited by tetcyclacis, an inhibitor regarded to be specific for cytochrome P-450 mono-oxygenases. The effect was dependent on the concentration of tetcyclacis and the duration of preincubation. The apparent rate of trans-membrane electron transport increased in the presence of catalase, indicating tetcyclacis-induced H2O2-production or additional tetcyclacis-independent H2O2 release. The findings suggest an interaction of cytochrome P-450 with the plasma membrane-located electron transport chain. This redox-chain could be involved in the degradation of abscisic acid, being located at the plasma membrane. This assumption is supported by the finding that ABA inhibits extracellular ferricyanide reduction.Keywords:
Ferricyanide
Lemna gibba
Lemna
L-Pipecolic acid was found to be effective in inducing flowering of Lemna paucicostata 151, 381, 441 and 6746, and of Lemna gibba G3. When the plants were grown on half-strength Hutner's medium, L-pipecolic acid caused profuse flowering of L. paucicostata 151 maintained under 9 and 10 h of light daily. In L. paucicostata 441 and 6746, L-pipecolic acid had a strong flower-promoting effect under a near critical photoperiod. In L. paucicostata 381, by contrast, L-pipecolic acid had only a very small effect on flowering. In L. gibba G3 substantial promotion of flowering was observed under continuous light. When one-twentieth-strength Hutner's medium was used as the basic medium, L-pipecolic acid stimulated flowering in all strains of Lemna examined, even under continuous light. When L. paucicostata 151 was grown on one-tenth-strength M medium or one-twentieth-strength Hutner's medium, the flower-inducing activity of L-pipecolic acid was greatly enhanced by cytokinin under continuous light. However, when this strain was grown with 9 h of illumination daily, this synergistic effect of cytokinin was only slight. A short-term (even 1-h) treatment with L-pipecolic acid resulted in flowering, suggesting that L-pipecolic acid is involved in the induction of flowering, rather than its evocation. D-Pipecolic acid also had flower-inducing activity, but its activity was 50 times lower than that of the L-isomer.
Lemna gibba
Lemna
Pipecolic acid
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Fusicoccin
Lemna gibba
Lemna
Chenopodiaceae
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Large changes in indole-3-acetic acid (IAA) levels occur during growth of Lemna gibba G-3 in sterile culture. The levels of IAA were measured in plants during a 45 day growth cycle using HPLC and isotope dilution analysis followed by selected ion current monitoring GC-MS analysis with 13C6-IAA as the internal standard. Even though the rate of plant growth remained constant over the entire growth period, IAA levels ranged from a high of 222 to a low of 6 nanograms per gram fresh weight. A Lemna mutant (jsR1) which has a giant phenotype was obtained by regeneration from primary callus cultures. Microspectrofluorometry of diamidino-2-phenylindole stained cells showed that jsR1 has the same amount of DNA per nucleus as the parent line (PL). All jsR1 cell types measured are about 1.5 times larger than in PL. The endogenous levels of IAA per gram fresh weight were higher in jsR1 at several stages of the plant culture cycle as compared to PL. This difference ranged from 1.2 to over 100 times as much. While PL showed only one high peak at day 9, jsR1 had IAA levels of 480 and 680 nanograms per gram fresh weight at days 9 and 45, respectively. Throughout the midculture stage of the growth cycle (20-28 days) both jsR1 and PL had IAA levels in the range of 9 to 14 nanograms per gram fresh weight. In contrast to PL, at day 45, jsR1 had no detectable ester or amide conjugates of IAA. These changes in IAA levels were determined in sterile plant cultures and thus cannot be attributed to bacterial or fungal activity.
Lemna gibba
Lemna
Indole-3-acetic acid
Dry weight
Callus
Lemna minor
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Abstract A long‐established axenic culture of Lemna gibba G3 was maintained in exponential growth phase under controlled conditions. Weekly analyses for 2 years showed that the individual plants of the Lemna gibba clone fluctuated between two forms. One extreme consisted of plants light in weight, small in size, and with a high relative growth rate (RGR), the other of heavy, large, and more slowly growing plants. At intervals plants having intermediate characteristics dominated in the stock culture. Indication of an annual growth‐cycle was also found. The magnitude of growth response (weight, RGR, area, and dry matter content) after treatment with abscisic acid (ABA), 6‐benzylaminopurine (BAP), and a combination of the two was different for low‐weight and heavy plants. The heavy plants were more sensitive to ABA and BAP treatment than the low‐weight ones. The accumulation of starch was least in small untreated plants and greatest in ABA treated plants. Large electron transparent globules were found in the chloroplasts of the ABA treated plants and in heavy plants regardless of how they had been treated. The different physiological and ultrastructural characteristics of the two forms of Lemna plants probably reflect an ageing‐rejuvenation cycle. Emphasis is placed on the importance of this cycle when Lemna is used as a model plant in physiological experiments.
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Lemna
Relative growth rate
Axenic
Dry weight
Lemna minor
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Four inhibitors of proteases, namely, bestatin, diisopropyl fluorophosphate, elastatinal and p-toluenesulfonyl-L-lysine chloromethyl ketone hydrochloride, were examined for their effects on flowering of a short-day plant Lemna paucicostata 6746 and a long-day plant Lemna gibba G3. Each of the inhibitors greatly inhibited the flowering of Lemna paucicostata 6746 that is normally induced by nitrogen deficiency. Bestatin or elastatinal given only during the first half of the culture period inhibited the flowering more clearly than when each was given during the latter half, suggesting that they inhibited the inductive process(es) involved in flowering rather than development of flower buds. Bestatin or elastatinal greatly inhibited the flowering of Lemna paucicostata 6746 induced by photoperiodic stimulus, ferricyanide and continuous far-red light. Simultaneous application of these two inhibitors was more effective in the inhibition of photoperiodically induced and ferricyanide-induced flowering than was each inhibitor alone. They also completely inhibited the photoperiodic flowering of Lemna gibba G3. These results suggest that the induction or activation of some proteases, probably followed by the degradation of some protein(s), is necessary for the induction of flowering in both these plants.
Lemna
Lemna gibba
Pharbitis nil
Flower induction
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The growth of broiler chickens on diets containing various levels of Lemna gibba was evaluated. Groups of broiler chicks were fed on diets containing 0-400 g Lemna gibba /kg for 3 weeks. These chickens were then changed to standard diets for a further 2 weeks. As the level of Lemna gibba increased, feed consumption and weight gain decreased. However, when diets were changed to the standard diet, compensatory growth was observed. In a second experiment, diets were formulated with a metabolizable energy of 5.02 MJ (1200 kcal)/kg Lemna gibba and included a finer-milled Lemna gibba. Chickens were fed on diets containing 0-300 g Lemna gibba /kg for 4 weeks. Each group was then divided into two subgroups. For the next 2 weeks one of these sub-groups was maintained on the experimental ( Lemna gibba ) diets (LL), while the other sub-group was changed to a standard diet (LS). Bird fed at levels above 150 g Lemna gibba /kg had decreased consumption and weight gain. These birds when changed to a standard diet tended to have increased weight gain compared with chickens continuously fed standard rations. LS birds had significantly higher weight gains and feed consumption and lower feed conversion than LL birds. In contrast to older birds, chicks fed on Lemna gibba at high concentrations showed growth retardation. When changed back to a standard diet they demonstrated normal or compensatory growth.
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Lemna
Lemna minor
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Abstract Putrescine (1,4-diaminobutane) accumulation in potassium (K)-deficient plants was considered to be one of the factors causing K deficiency symptoms in plants. However, experiments using aseptic cultures of Lemna paucicostata 6746 and Lemna gibba G3 (duckweeds) led to opposite results; the growth of the plants under K deficiency recovered to some extent when putrescine was administered, although the content of putrescine in these plants was considerably higher than that in the plants which did not receive putrescine. Thus it is inferred that putrescine does not cause K deficiency symptoms but that it plays a role in the replacement of K as an organic cation in K-deficient plants. Experiments using putrescine biosynthesis inhibitors also in part supported this hypothesis. Key Words: Lemna gibba Lemna paucicostata potassium deficiencyputrescine
Lemna
Lemna gibba
Potassium deficiency
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Lemna minor
Lemna gibba
Lemna
Frond
Phytotoxicity
Axenic
EC50
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Fifteen strains of subgenus Lemna, collected in ponds and ditches in the western part of The Netherlands, strain G3 (previously described as Lemna gibba) and strains 6573 and F (previously described as Lemna minor) were aseptically cultured on M-medium in the presence and absence of EDDHA. When cultivated on EDDHA medium the strains showed a marked variation in the degree of gibbosity, whereas in the absence of the chelate all strains were more or less flat. The strains could be divided into two groups as far as the degree of gibbosity in the presence of EDDHA was concerned. There were no consistent differences in morphology between the two groups if cultured on the nutrient medium devoid of EDDHA. In the light of the present investigation distinction between Lemna gibba and Lemna minor seems not always possible.
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Lemna minor
Lemna
Morphology
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The duckweeds Lemna gibba L. and Lemna minor L. only grew well in undisturbed culture under axenic conditions in low light intensity when provided with a suitable energy source such as glucose. In media containing N03-N gibbosity (a convex ventral surface) was induced in the presence of the chelating agent ethylene-diamine-di-o-hydroxyphenylacetic acid (EDDHA). In nutrient solutions containing NO3-N as the only N source, but without EDDHA, L. gibba occasionally exhibited gibbosity in culture solutions of 40 cm3 volumes. More fronds were induced to exhibit gibbosity when the volume of the culture medium was increased from 40 cm3 to 200 cm3. Gibbosity was never induced in L. minor, neither was it induced in L. gibba in media containing NH4-N, even in the presence of NO3-N. There was no direct correlation between the occurrence of gibbosity and frond growth rate, but gibbosity occurred only when there was good frond growth. In the absence of a sugar, frond growth was enhanced by bubbling air through the culture solution in the light. Increasing the CO2 concentration in the air up to 1% enhanced growth and induced gibbosity. Carbon dioxide did not induce gibbosity in media containing NH4-N.
Lemna gibba
Lemna
Frond
Axenic
Lemna minor
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