Normal Nutrient Solution Research Articles

A study of the transpiration surfaces of Avena sterilis L. var. Algerian leaves using monosilicic acid as a tracer for water movement

The sites and pathways of transpiration from leaves of Avena sterilis L. var. Algerian were studied using the accumulation of monosilicic acid as a tracer for water movement. Seedlings of Algerian oats were grown under silicon free conditions and fed monosilicic acid, in a normal nutrient solution, via the roots. The silicon component of monosilicic acid was located in freeze substituted tissue by means of x-ray microprobe analysis. Methods of tissue fixation preventing post treatment movement of tracer were developed and it was determined that monosilicic acid is a suitable tracer for water.Sites of water loss were marked by accumulation of silicon. Internal evaporating surfaces having a high intensity of water loss were demonstrated. Evaporation from epidermal surfaces was most intense over the guard and subsidiary cells with very little evaporation from the cuticular surfaces of normal epidermal cells. Moderately high evaporation occurred from epidermal fibre cells located above the veins. Evaporation from all exposed walls of guard cells including the wall adjacent to the pore was intense. Smaller amounts of tracer were located in the unexposed anticlinal walls of epidermal cells as well as within the unexposed walls of mesophyll cells. The results are interpreted as demonstrating the extent of internal transpiration surfaces and that cuticular epidermal transpiration is low. Strong support is given to the existence of peristomatal transpiration. Internal pathways of water movement are defined and the occurrence of these is discussed in relation to cuticular transpiration and lateral water movement in the epidermis.

Effect of full agonists following calcium deprivation in rat vas deferens.

The contractile effects of maximum doses of adrenaline, noradrenaline, methacholine, acetylcholine, serotonin and barium chloride were studied following substitution of a medium without calcium for the normal nutrient solution. Except for the last agonist, the effects fall to about 10% within the first 3 min with prompt return to normal value upon reintroduction of regular fluid. This recovery is, however, slower if the previous incubation in Ca-free solution is prolonged. When barium chloride is used in a calcium-free medium, the maximum height of contractions falls exponentially at a t1/2 of about 180 min. This decay can be accelerated by giving successive 5-min doses of the agonist or by using EDTA. It is hypothesised that excitation--contraction coupling in rat vas deferens depends on at least two different calcium sources: a deep site associated with the effects of barium, and a superficial one, related to the other agonists. To explain the slow recovery after prolonged calcium lack, a third compartment in series with the latter is suggested. No indication is found that the biphasic effects of barium depend on two different calcium pools.

The influence of water stress on the metabolism of diatoms I. Osmotic resistance and proline accumulation in Cyclotella meneghiniana

Summary The velocities of growth, respiration and photosynthesis under osmotic stress in the diatom Cyclotella meneghiniana were investigated. Thereby, optimum growth was observed in a medium of 0.5 osmolar concentration. Growth was also exhibited in dilutions up to 0.125 osmolarity and in increased concentrations up to 1.4 osmolarity. Respiration and photosynthesis, compared to the normal nutrient solution, showed a constant decrease under increased osmotic stress. In the case of photosynthesis, a recovery effect was observed after three hours of stress influence. In algae cell extracts no increase in Na+ and Cl- ions, after several hours of osmotic stress, could be determined (end cone. = 1.1 osmolarity). After one hour of photosynthesis in 14CO2 the algae were transferred to a fresh nutrient solution, followed by addition of the osmotically active substance to one of the two parallel samples (end conc. = 1.1 osmolarity). At different times an aliquot was taken from the respective samples and analyzed by thin-layer chromatography for their qualitative and quantitative composition. Above all, two spots showed increased radioactive marking thereby. These could be identified as A'-pyrroline-5-carbonic acid (P5C) and proline. If the stress was again partially relieved, then the proline content also showed a decrease. The effect of proline accumulation could be achieved with NaCl and sorbitol as osmotically active substances, but not with glycerol and polyethyleneglycol (M. W. 200).

A Method to Compare the Effect of Ionic Iron and Iron Chelates in Nutrient Solution Cultures

A method is described by which the effect of chelated Fe can be compared with the effect of ionic Fe in nutrient solution cultures over a prolonged period of time. Plants are grown in two solutions in succession: the one containing all nutrient elements except Fe, the other one containing the Fe compound together with Ca(NO(3))(2). In experiments with soybeans (Glycine maxima (L.) Merr.) and with corn (Zea mays L.) it was shown that a 7-day cycle with the ratio of 4 days nutrient solution to 3 days Fe solution resulted in growth and Fe nutrition similar to plants grown with a normal nutrient solution.

Mechanism of spasmolytic action of 4-methylumbelliferone

The present experiments were undertaken to investigate the mechanism of spasmolytic action of 4-methylumbelliferone (4-MU). It has been reported that the spasmolytic actions of trihydroxybenzene derivatives and trihydroxypropiophenone (THPP) in the biliary system are partially due to the inhibition of catechol-O-methyltrasferase (COMT) activity. On the other hand, resorcinol, a dihydroxybenzene isomer is used as a synthetic material for 4-MU. Utilizing epinephrine as a substrate and S-adenosylmethionine as a methyl donor, the effects of pyrogallol and 4-MU on rat liver COMT activity were determined. Pyrogallol showed inhibition of enzyme activity depending on the concentration added, however, 4-MU was ineffective at any concentration. Contractile responses of the isolated rabbit aorta to transmural electrical stimulation and exogenously applied epinephrine were potentiated by pretreatment with pyrogallol, but were rather inhibited at high concentrations of 4-MU. The phasic and tonic contractions in the isolated rabbit sphincter of Oddi induced by KCl in normal nutrient solution were little affected by either THPP or 4-MU in low concentrations, but were inhibited, in high concentrations. On the other hand, these contractions were inhibited by papaverine in any concentration, but not so by atropine. The contractile responses of the isolated rabbit sphincter of Oddi to CaCl2 and BaCl2 in Ca++ free medium were significantly inhibited by THPP, papaverine and 4-MU, but not so by atropine. The transmural electrical stimulation applied to the sphincter of Oddid caused contractions of the two components, the initial one during stimulation and the other following stimulation. These two components were inhibited by papaverine and 4-MU, depending on the concentration added, but were only slightly inhibited by THPP in high concentrations. It was observed, however, that atropine usually converted the initial component to a relaxation. The late component was unaffected by atropine. The mechanism of spasmolytic action of 4-MU has been discussed herein.

Water and Salt Stresses, Kinetin and Protein Synthesis in Tobacco Leaves

The capacity of tobacco (Nicotiana rustica) leaf discs to incorporate l-leucine (14)C into proteins was measured. Leaf discs were obtained from plants which experienced soil water depletion, or which were exposed to a saline or osmotic stress in the root medium. The stresses were brief of relatively short duration and water potential did not decrease below 4 bars in the root media. Leaf discs were sampled 2 hours after stress removal, achieved by reirrigation, or replacement of saline and osmotic solutions with normal nutrient solution. Plants were always turgid when leaves were sampled.All stressed tissues showed reduced capacity to incorporate l-leucine (14)C into protein. The reduction was about 50% and could not be attributed either to reduced uptake into the discs, or to possible isotopic dilution. Incorporation decreased progressively with leaf age in control discs as well as in stressed leaf discs. At all ages tested, incorporation in stressed discs was lower than that of the control. Full recovery of incorporation capacity in stressed discs was obtained when discs were sampled 72 hours after stress removal but not earlier.Kinetin pretreatment prior to incubation with labelled leucine partially restored incorporation in stressed discs. The differences in response to kinetin of stressed and control discs suggest a lower endogenous level of cytokinins in the stressed discs. The results were qualitatively similar regardless of the kind of stress given to the plants during pretreatment. This supports the hypothesis that the normal supply of root cytokinins is important in shoot metabolism.