Identification of jasmonic acid in Mimosa pudica and its inhibitory effect on auxin- and light-induced opening of the pulvinules

Jasmonic acid was identified from Mimosa pudica L. plants by mass spectrometry, high performance liquid chromatography and thin layer chromatography. Effects of authentic jasmonic acid on pulvinule movement and transpiration of the pinnae were compared with those of abscisic acid. Jasmonic acid and abscisic acid each at 10⁻⁵ M inhibited both auxin- and light-induced opening of the pulvinules. A closure-inducing activity of jasmonic acid at 10⁻⁴ M was greater than that of abscisic acid at 10⁻⁴ M. Pinnae transpiration was reduced by 10⁻⁵ M abscisic acid but not by 10⁻⁴ M jasmonic acid.     

Effect of CO2-enrichnient on seedling physiology and growth of two tropical tree species

Seedlings of two tree species from the Atlantic lowlands of Costa Rica, Ochroma la-gopus Swartz, a fast-growing pioneer species, and Pentaclethra macroloba (Willd.) Kuntze, a slower-growing climax species, were grown under enriched atmospheric CO₂ in controlled environment chambers. Carbon dioxide concentrations were maintained at 350 and 675 μl 1⁻¹ under photosynthetic photon flux densities of 500 μol m⁻² s⁻¹ and temperatures of 26°C day and 20°C night. Total biomass of both species increased significantly in the elevated CO₂ treatment; the increase in biomass was greatest for the pioneer species, O. lagopus . Both species had greater leaf areas and specific leaf weights with increased atmospheric CO₂. However, the ratio of non-pho-tosynthetic tissue to leaf area also increased in both species leading to decreased leaf area ratios. Plants of both species grown at 675 μl 1⁻¹ CO₂ had lower chlorophyll contents and photosynthesis on a leaf area basis than those grown at 350 μl 1⁻¹. Reductions in net photosynthesis occurred despite increased internal CO₂ concentrations in the CO₂-enriched treatment. Stomatal conductances of both species decreased with CO₂-enrichment resulting in significant increases in water use efficiency.     

The effect of benzo-18-crown-6, a synthetic ionophore, on stomatal opening and its interaction with abscisic acid

Abstract. Treatment of tomato seedlings with 5 mM benzo-18-crown-6, a potassium ionophore, produced a reduction in transpiration of 40%. Treatments of epidermal strips of Commelina communis with ben-zo-18-crown-6 (1-l0mM) inhibited stomatal opening, and this effect was shown to be reversible. An antagonistic interaction between abscisic acid (10⁻⁷M) and benzo-18-crown-6 (4 × 10⁻³ M) was also observed.     

Effect of protective solutes on leakage from and survival of immobilized Lactobacillus subjected to drying, storage and rehydration

When lactic acid bacteria are used industrially as fermentation starters it is important to obtain stable and highly viable bacterial cultures. Six strains of Lactobacillus encapsulated in Ca-alginate gel beads were investigated to determine whether dehydration, storage and rehydration may inflict injury. A negative relationship between leakage of lactate dehydrogenase and survival rates was found. Mesophilic lactobacilli showed only negligible leakage compared with thermophilic strains when dehydrated at 30 °C to a level of 0·11 g H₂0 (g dry wt)⁻¹. The choice of an appropriate suspending medium to be introduced before drying was therefore very important for thermophilic lactobacilli in order to increase the survival rates during dehydration, storage and rehydration. The osmoregulatory solutes tested were adonitol, betaine, glycerol and reconstituted non-fat milk solids (NFMS). Less injury was inflected during dehydration for Lactobacillus helveticus with adonitol, glycerol and NFMS. Survival rates for the strains subjected to immobilization, dehydration, storage and rehydration varied with the strain and the protective solute when fluidized-bed drying was used at 5 °C to a level as high as 0·34 g H₂0 (g dry wt)⁻¹. Non-fat milk solids gave the best protection for thermophilic lactobacilli, while adonitol and NFMS were best for mesophilic lactobacilli.     

Acute effects of the sodium salt of 2,4-D on the early developmental stages of bleak, Alburnm alburnus

The acute effects of a herbicide based on 2,4-D on embryos and larvae of bleak, Alburnus alburnus L. exposed to concentrations of 25–3200 mg 1⁻¹ for 12–48 hours were investigated. The 2,4-D delayed or stopped the development of embryos in their early stages, caused behavioural changes and morphological alterations. The L.C.₅₀ values for embryos varied between 12–9 and 15·9–4mg 1⁻¹ and for larvae from 51·6 to 111·2mg 1⁻¹ according to the time of exposure. The level of 2,4-D in Lake Balaton, or similar shallow lakes, without substantial injury of the littoral fish fauna should not surpass 0·5–1·0 mg 1⁻¹.     

Effect of 2,5-norbornadiene on abscission and ethylene production in citrus leaf explants

Citrus ( Citrus sinensis L. Osbeck) leaf explants completely abscise within 48 h when exposed to saturating amounts of ethylene at 25°C. When 2,5-norbornadiene was added, 2000 μl 1⁻¹ reduced abscission of explants also exposed to 2 μl 1⁻¹ of ethylene to the level of the control, and 8000 μl 1⁻¹ reduced abscission in explants exposed to 10 μl 1⁻¹ of ethylene to the level of the control, but abscission was complete when 1 000 μl 1⁻¹ of ethylene was used in the presence of 8 000 μl 1⁻¹ of 2,5-norbornadiene. When explants were exposed to 2 μl 1⁻¹ of ethylene, 2000 μl 1⁻¹ of 2,5-norbornadiene prevented abscission if applied up to 10 h after exposure to ethylene. After 18 h, applied 2,5-norbornadiene had little effect on abscission at 48 h. A Lineweaver-Burk plot gave a 1/2 maximum value of 0.12 μl 1⁻¹ for ethylene on abscission, 2,5-Norbornadiene gave competitive kinetics with respect to ethylene with a K₁ value of approximately 120 μl 1⁻¹ of 2,5-norbornadiene. The presence of 2,5norbornadiene stimulated ethylene production, which progressively increased as the 2,5-norbornadiene concentration was increased from 250 to 8 000 μl 1⁻¹ 2,5-Norbornadiene also suppressed the induction of cellulase and polygalacturonase by ethylene. Together, 2,5-norbornadiene and 2,4-dichlorophenoxyacetic acid were more effective than either alone in reducing abscission. 2,5-Norbornadiene also was effective in preventing the reduction of indole-3-acetic acid transport induced by ethylene.     

EFFECTS OF CADMIUM TOXICITY ON GROWTH AND ELEMENTAL COMPOSITION OF MARINE PHYTOPLANKTON

Some classes of marine phytoplankton are believed to be more tolerant of high concentrations of trace metals than others, but the results of experimental tests of this hypothesis are ambiguous. Eleven species of phytoplankton representing five classes were grown in Aquil medium containing Cd concentrations between 10⁻⁸ and 10⁻⁵ M ([Cd²⁺]= 10^−9.85 to 10^−6.84 M), and growth rates and intracellular concentrations of Cd, C, N, and S were measured. The mean Cd²⁺ concentration (pCd⁵⁰) that reduced the growth rate of each species to 50% of its maximum varied by 2.5 orders of magnitude, from 10^−6.23 for Emiliania huxleyi to 10^−8.79 for Synechococcus sp. Taxonomic trends in Cd resistance were not apparent in these data. Cadmium quotas (mol Cd·L⁻¹ cell volume) were lowest in species of Bacillariophyceae (ANOVA, P < 0.001), suggesting that they might regulate Cd transport differently than other taxa. Cellular S:C molar ratios increased in four of seven phytoplankton grown at high pCd (7.37–6.84) compared to low Cd ion concentrations (no added Cd), a result of increases in S·L⁻¹ cell volume. Nitrogen:carbon molar ratios were also higher in Cd-exposed phytoplankton, as changes in N and S were highly correlated ( r = 0.98, P < 0.0001). In two species that were examined, S:C ratios increased as a linear function of increasing Cd concentration. The results demonstrate large variability in Cd resistance among phytoplankton that is primarily a function of interspecific differences in Cd detoxification.     

Enzymes involved in ammonia assimilation in the fungus Acremonium persicinum

Abstract Acremonium persicinum grown in batch culture with ammonium tartrate as the nitrogen source possessed an NADP⁺-dependent glutamate dehydrogenase and a glutamine synthetase. Glutamate synthase was not detected under the culture conditions used. Kinetic studies of the NADP⁺-dependent glutamate dehydrogenase at 25°C and pH 7.6 revealed an apparent K _m of 3.2 × 10⁻⁴ M for 2-oxoglutarate and an apparent K _m of 1.0 × 10⁻⁵ M for ammonium ions, with corresponding apparent V _max values of 0.089 and 0.13 μmol substrate converted/min/mg of protein, respectively. Glutamine synthetase was measured by the γ-glutamyl transferase reaction at 30°C and pH 7.55. This transferase reaction of glutamine synthetase had a higher rate at 30°C than at 25°C or 37°C.     

Scaling of oxygen consumption of Lake Magadi tilapia, a fish living at 37°C

Rates of oxygen consumption were measured in the geothermal, hot spring fish, Oreochromis alcalicus grahami by stopped flow respirometry. At 37° C, routine oxygen consumption followed the allometric relationship: V o₂=0.738 M ^0.75, where V o₂ is ml O₂ h ⁻¹ and M is body mass (g). This represents a routine metabolic rate for a 10 g fish at 37° C of 0.415 ml O₂ g⁻¹ h ⁻¹ (16.4 μmol O₂ g ⁻¹ h ⁻¹). Acutely increasing the temperature from 37 to 42° C significantly elevated the rate of O₂ consumption from 0.739 to 0.970 ml O₂ g ⁻¹ h ⁻¹ ( Q ₁₀=l.72). In the field, O. a. grahami was observed to be 'gulping' air from the surface of the water especially in hot springs that exceeded 40° C. O. a. grahami may utilize aerial respiration when O₂ requirements are high.     

Photoperiod and light quality effects on rate of dark respiration and on photosynthetic capacity in developing seedlings of Chenopodium rubrum

Development and acclimation of energy transduction were studied in seedlings of Chenopodium rubrum L. ecotype selection 184 (50° 10' N; 105° 35' W) in response to photomorphogenic and photoperiodic treatments. Dark respiration and photosynthetic capacity [nmol O₂ (pair of cotyledons)⁻¹ h⁻¹] were measured with an oxygen electrode. Changes in chloroplast ultrastructure were analyzed concomitantly. After germination, seedlings were grown at constant temperature either in darkness or in continuous light (white, red, far-red and blue) or were subjected to diurnal cycles of light/dark or changes in light quality. Dark respiration was low in far-red light treated seedlings. In red light treated seedlings dark respiration was high and the mean value did not depend on fluence rate or photoperiod. Blue light stimulated transitorily and modulated dark respiration in photoperiodic cycles. Photosynthetic capacity was reduced by far-red light and increased by red light. In response to blue light photosynthetic capacity increased, with indications of a requirement for continuous energy input. Phytochrome and a separate blue light receptor seemed to be involved. In continuous red light a clear cut circadian rhythm of dark respiration was observed. Blue light had a specific effect on chloroplast structure.     

Hardening, abscisic acid, proline and freezing resistance in two winter wheat varieties

Two varieties of winter wheat ( Triticum aestivum L.) differing in freezing resistance ("Holme" from Sweden, freezing resistant, and "Amandus" from Germany, less freezing resistant) were hardened for five weeks by gradually reducing the day/night temperature from 20°C/15°C during the first week to 2° C/0° C during the fifth week and the photoperiod from 15 to 9 h. This treatment increased the freezing resistance of both varieties in comparison to unhardened control plants. Hardening caused an increase in osmolarity of cell sap and in the levels of proline and abscisic acid (ABA). Increase in osmolarity preceded the increase in ABA level, and proline levels increased later than ABA levels. Holme had higher values of osmolarity as well as higher levels of ABA and proline. but the differences between the two varieties were significant only for proline. Since the pressure potential remained constant or increased slightly during the hardening period, it is suggested that the accumulation of ABA is due to the hardening process and not to simple water stress caused by cold-induced inhibition of water uptake by the root.
Spraying hardened plants with 10⁻⁴ M ABA 24 h before a freezing test increased freezing resistance in both varieties, but did not obliterate the differences in freezing resistance between the two varieties. Spraying hardened plants with an aqueous proline solution (10%, w/v) was without effect on freezing resistance. It is concluded that the hardening procedure causes an accumulation of ABA in winter wheat leaves and that ABA is involved in the chain of events leading to freezing resistance.     

Changes in phenolic acids and abscisic acid in sugar pine embryos and megagametophytes during stratification

The phenolic acids and abscisic acid (ABA) of sugar pine ( Pinus lambertiana Dougl.) embryos and megagametophytes, separated by high-pressure liquid chromatography, were analyzed during 90 days stratification of the seeds. The phenolic acids occurred mainly as glycosides. Following hydrolysis, the majority of phenolics present could be identified as common benzoic and ciranamic acid derivatives. Levels of phenolic acids were relatively low in dormant seeds, but increased substantially in the embryos during stratification at 5°C, particularly cinnamic acid, p -coumaric acid, ferulic acid, and one unknown. This active synthesis during stratification did not support an inhibitory function for phenolic acids. During stratification at 5°C, changes in ABA levels in both tissues followed a triphasic pattern, with no loss during the first 30 days, a significant decrease the second 30 days, and a lesser decrease the last 30 days. Loss of ABA from moist seeds at 25°C occurred three times as rapidly, so that by 30 days the ABA level of these seeds was equivalent to that of seeds stratified 90 days at 5°C; however, dormancy was not alleviated at 25°C. Application of exogenous ABA (10⁻⁷ to 10⁻⁴M) to stratified seeds did not significantly reduce germination. Together, the above results did not support a primary role for ABA in the maintenance of dormancy in sugar pines.
A correlated increase in phenylpropanoid metabolism and respiratory capacity with increased germinability during stratification suggests that loss of dormancy may be more closely dependent on increased levels of growth promoters or shifts in metabolic pathways.     

Chilling injury in coleus as influenced by photosynthetically active radiation, temperature and abscisic acid pretreatment. I. Morphological and physiological responses

Abstract. Coleus blumei Benth. (PI No. 354190), a green-leafed cultivar, was exposed to 5°C for 48 or 72 h after pretreatment for 48 h at two levels of photosynthetically active radiation (PAR) (8 and 320 μmol s⁻¹ m⁻²), two temperatures (13 and 20°C), and two abscisic acid (ABA) levels (0 and 200 g m⁻³ of the racemic mixture). Plants given low PAR for only 48 h prior to chilling treatment (48 or 72 h at 5°C) showed increased protection against chilling injury while those given high PAR were severely injured. The former plants were darker green, contained greater concentrations of chlorophyll- a , chlorophyll- b , total chlorophyll and anthocyanin and generally had a lower abscission rate than the latter plants. There were no differences, however, in chlorophyll- a/b ratio among plants grown at the two PAR levels, two temperatures or two ABA concentrations. Temperature and ABA pretreatment and number of hours at 5°C had no significant effect on chilling injury as measured by leaf chlorosis, but generally had a significant effect on leaf abcission, especially at 3 and 7 d after returning the plants to the greenhouse. Enclosing intact plants or excised shoots in plastic bags to maintain 100% relative humidity during 72 h chilling treatment failed to provide protection against chilling injury. These findings indicate that the protective effects of low PAR applied prior to chilling treatment may be as important or more important than that applied during chilling. They also indicate the importance of making careful measurements of PAR levels when conducting studies on chilling injury.     

Subject index volume 144

Abstract β-xylosidase (EC 3.2.1.37) has been purified from Aspergillus nidulans mycelium grown on oat-spelt xylan as sole carbon source. Its pH optimum for activity was found to be 5.0 and the optimum temperature was 50 °C. Its molecular mass was estimated by gel filtration to be 180000. Using p-nitrophenyl-β-d-xylopyranoside as substrate, the K _m and V _max values have been found to be 1.1 mM and 25.6 μmol min⁻¹(mg protein)⁻¹, respectively. Enzyme activity was inhibited by Hg²⁺, Ag²⁺, and Cu²⁺ at a concentration of 1 × 10⁻³ M. The synthesis of β-xylosidase in A. nidulans is strongly induced by arabinose and xylose and is subject to carbon catabolite repression mediated by the cre A gene product.     

Potato cold hardiness development and abscisic acid. I. Conjugated abscisic acid is not the source of the increase in free abscisic acid during potato (Solanum commersonii) cold acclimation

Free and conjugated abscisic acid (ABA) levels in stem-cultured plantlets of potato ( Solanum commersonii Dun, PI 458317) during cold acclimation were measured. The levels of free and conjugated ABA were measured by an enzyme immunoassay (EIA) with rabbit anti-ABA-serum. The use of immunoglobulin G fraction purified from rabbit antiserum and the methylated form of ABA resulted in an improved measuring range (0.01 to 10 pmol ABA) and precision (slope of logit-log plot, −1.35) of EIA, compared to the use of antiserum and free ABA. Estimates of the EIA were consistent with those resulting from a commercial EIA. Under a 4/2°C (day/night) temperature regime, the potato plantlets increased cold hardiness from −5°C (warm-grown control) to −10°C by the 7th day. During the same period, there were two transitory increases in free ABA, the first one three-fold from 1.5 to 5.3 nmol (g dry weight)⁻¹ on the 2nd day and the second one five-fold from 1.5 to 7.6 nmol (g dry weight)⁻¹ on the 6th day. Each increase in ABA concentration was followed by an increase in cold hardiness. There was no significant change in conjugated ABA content (4.2±0.6 nmol [g dry weight]⁻¹) throughout the cold acclimation period. The lack of an interrelationship between levels of free and conjugated ABA suggested that the transitory increase in free ABA during cold acclimation was not a result of the conversion of conjugated ABA. The increase in free ABA due to biosynthesis of ABA during potato cold acclimation is discussed.     

Oxygen uptake in developing eggs and larvae of the cod, Gadus morhua L.

Unfertilised cod eggs showed a mean oxygen uptake rate at 5°C of 0.089 μl O₂, dry wt.⁻¹ h⁻¹; this gradually rose to 0.768 μl O₂ mg dry wt.⁻¹ h⁻¹ in eggs about to hatch. From hatching to complete yolk absorption larvae respired at 1.6 μl O₂, mg dry wt.⁻¹ h⁻¹. During starvation following yolk absorption, uptake fell significantly to 1.1 μl O₂, mg dry ⁻¹ h⁻¹. Much of this decrease in oxygen consumption was shown to be caused by reduction in activity. Loss of weight during the embryo and larval phases could not easily be reconciled with total oxygen consumption; it is suggested that cod embryos and larvae may not rely solely upon endogenous energy reserves during development.     

Latitudinal cline of requirement for far‐red light for the photoperiodic control of budset and extension growth in Picea abies (Norway spruce)

To test for the effects of far‐red light on preventing budset in Picea abies , seedlings of six populations originating from latitudes between 67°N and 47°N were grown for 4–8 weeks in continuous incandescent (metal halogen) light at 300 µmol m⁻² s⁻¹ and 20°C and then transferred, at the same temperature, to a daily regime of 8 h incandescent light (300 µmol m⁻² s⁻¹) followed by 16 h cool white fluorescent light (40 µmol m⁻² s⁻¹). (Cool white lamps are deficient in far‐red light, with a R/FR ratio of 7.5 compared with 2.0 for the incandescent lamps.) All the seedlings from 67° and 80% of those from 64° stopped extension growth and set terminal buds within 28 days of the change of regime. The seedlings from 61° and further south continued growing, as did control seedlings from 67° grown as above but with incandescent light at 20 µmol m⁻² s⁻¹ replacing cool white illumination. To distinguish between a clinal and ecotypic pattern of variation, the interval between 64° and 59° was investigated by growing populations originating from that area in the same regimes as before. After 28 days in the cool white day‐extension regime, the percentage budset was 86 for the population from 64°, 0 for the population from 59° and 25–50 for the intermediate populations; i.e. the populations showed a clinal variation in requirement for far‐red light according to latitude. Thus northern populations of Picea abies appear to behave as 'light‐dominant' plants for the photoperiodic control of extension growth and budset, whereas the more southern populations behave as 'dark‐dominant' plants.     

Effects of phenolic acids on ammonia oxidation by terrestrial autotrophic nitrifying microorganisms

Abstract It has been hypothesized that vegetation in certain ecosystems inhibits nitrification in soil by producing phenolic compounds that inhibit oxidation of ammonia by nitrifying microorganisms. This hypothesis is based largely on a report that very low concentrations (10⁻⁶ M–10⁻⁸ M) of several phenolic acids (notably ferulic acid) completely inhibited NO₂⁻ production in an aqueous suspension of soil treated with (NH₄)₂SO₄ and a nutrient solution suitable for growth of Nitrosomonas and other autotrophic nitrifying microorganisms. To evaluate this hypothesis, we determined the effects of three ohenolic acids (ferulic acid, caffeic acid, and p -coumaric on nitrite production by representatives of three genera of terrestrial autotrophic nitrifying microorganisms ( Nitrosospira, Nitrosomonas , or Nitrosolubos ) grown on a defined medium containing NH₄⁺. We found that nitrite production by the Nitrososspira was not inhibited by ferulic acid, caffeic acid, or p -coumaric acid at concentrations of 10⁻⁶ or 10⁻⁵ M and was only slightly inhibited when these acids were at a concentration of 10⁻⁴ M. We also found that ferulic acid did not markedly inhibit nitrite production by the three genera of nitrifying microorganisms studied, even when its concentration was as high as 10⁻³ M. These observations invalidate the hypothesis tested because the phenolic acids studied did not significantly retard ammonia oxidation by autotrophic microorganisms even when their concentration in cultures of these microorganisms greatly exceeded their concentrations in soils.     

Effects of development, temperature and salinity on metabolism in eggs and yolk-sac larvae of milkfish, Chanos chanos (Forsskål)

Oxygen uptake rates and yolk-inclusive dry weiGhts were measured during the egg and yolk-sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk-sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk-sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk-sac stage at 23.28 and 33°C.
Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O₂ egg ⁻¹ h ⁻¹;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O₂ larva ⁻¹ h⁻¹ at 23, 28 and 33°C, respectively; Q₁₀= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q ₁₀= 1.69–3.58) and yolk-sac larvae (Q ₁₀=2.55). Salinity did not affect metabolic rates.
Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q ₁₀= 2.25).