A comparison between ammonium and nitrate nutrition of young sugar-beet plants grown in nutrient solutions at constant acidity. 1. Production of dry matter, ionic balance and chemical composition.

Diploid sugar beet was grown in nutrient culture with ammonium and nitrate N in solutions kept at constant pH by automatic titration. Since plants given nitrate N yielded only 12% more than those given ammonium N, the effects of form of N on plant chemical composition could be determined. The excess of cations in the plant (C-A) was >3 times as great in plants given nitrate as in those given ammonium. The acidity evolved into the culture medium was a good measure of ammonium uptake, whereas with nitrate the amount of alkalinity evolved was unrelated to and small in comparison with the amount of nitrate absorbed. The rate of H+ production decreased during darkness and that of OH- decreased during or just after the dark phase. Levels of soluble carbohydrates in plants given nitrate were over twice as high as in those given ammonium. Data are given on levels of 6 organic acids, K, Na, Ca Mg, P, S and Cl. (Abstract retrieved from CAB Abstracts by CABI’s permission

A comparison between ammonium and nitrate nutrition of young sugar-beet plants grown in nutrient solutions at constant acidity. 2. Effect of light and carbohydrate supply.

The effect of light and of glucose in the nutrient medium on the release of OH- or H+ and on ion accumulation by sugar beet plants grown with NO3 or NH4 nutrition was studied at a constant pH of 5.50. Decrease in OH- production rate in the dark was probably caused by retarded nitrate assimilation or carbohydrate shortage in the roots. Decrease in the rate of H+ production (NH4 uptake) in the dark was probably due to carbohydrate depletion. Both 24-h illumination and the addition of glucose increased H+ production during NH4 uptake and OH- production during NO3 uptake. 24 h darkness decreased the carboxylate pool on both N sources and it was tentatively concluded that light and darkness exert more influence on the carboxylate pool than N assimilation. Relationships between organic acid, carbohydrate and N metabolism, H+ or OH- production and inorganic composition were considered in detail. (Abstract retrieved from CAB Abstracts by CABI’s permission

Nitrate reductase activity and oxalate content of sugar-beet leaves.

Diploid sugar beet was grown in controlled environment at 25/17 deg C in 14-h photoperiods in well aerated, regularly changed nutrient solution containing 6 meq NO3/l. When 6 leaves had been expanded, the total carboxylate content of the oldest leaf (leaf 1) was found to be 5836 meq/kg DM, while that of leaf 6 was only 2312 meq/kg; the difference was mainly due to oxalate content, which was 5236 meq/kg in leaf 1 and 1744 meq/kg in leaf 6. Nitrate-N content was about 50% higher in leaf 1 than in leaf 4. Nitrate-reductase activity fell to very low values as leaves aged. Experiments in which young and old leaf material was mixed, or oxalate at 0-4000 meq/kg DM was added to leaf samples, showed that oxalate had no substantial effect on nitrate-reductase activity. (Abstract retrieved from CAB Abstracts by CABI’s permission

Regulatie van de fytomorfogenese : achtergronden en toepassingen

The publication consists of seven chapters: Coordination of cell division during plant regeneration; hormonal regulation of differentiation in tissue cultures; root regeneration in apple tissue cultures; metabolism and activity of cytokinins in bulbous iris; physiology of rose flower bud opening; effects of light colour in horticulture; research on growth substances in a bird's-eye view, 1960-1990

Carboxylates and the uptake of ammonium by excised maize roots

The effect of carboxylates (organic acid anions) on NH 4 uptake was studied by changing the carboxylate level of roots prior to uptake experi ments. Succinate was the most effective stimulator of ammonium uptake. The oxocarboxylates (α-oxoglutarate, oxaloacetate and pyruvate) and malate also promoted NH 4 entry. Preloading of roots with citrate, acetate, oxalate, glyoxylate or malonate reduced subsequent ammonium uptake. It is concluded that oxocarboxylates are important compounds in both the assimilation and the uptake process of ammonium. All carboxylates tested enhanced K uptake, but repressed NO 3 uptake, except citrate which increased nitrate absorption. Carboxylate stimulation of NH 4 entry showed metabolic as well as non-metabolic aspects

Nitrogen and energy balance of a short-rotation poplar forest system.

The mean annual dry matter production of a short-rotation poplar forest in the Netherlands was 14.4 tonnes ha-1 during a 5-year growing period. During the growing period trees took up 542 kg N ha-1 of which 64 % was in the bole and branches. In the 5th year denitrification was measured in undisturbed columns in the field by the acetylene-inhibition technique. An annual denitrification rate of 18 kg N ha-1 was estimated on the basis of the observed N2O profile. The system needed an annual input of 122 kg N ha-1 to balance the nitrogen budget. The energy balance showed that at the present dry matter production the system had a net output of 54 GJ ha-1 year-1. An increase in dry matter production to a maximum of 25 tonnes ha-1 year-1, possible by planting the trees at a higher density, would raise the net energy output to 97 GJ ha-1 year-1, in spite of higher energy inputs associated with fertilizer applications. (Abstract retrieved from CAB Abstracts by CABI’s permission

Socioeconomic differences in stroke among Dutch elderly women: the Rotterdam Study

BACKGROUND AND PURPOSE: We sought to assess the association between socioeconomic status and the risk of stroke among elderly women. Methods--The association between socioeconomic status and stroke emerged in cross-sectional and longitudinal data on 4274 female participants of the Rotterdam Study, a prospective, population-based, follow-up study in the Netherlands among older subjects. RESULTS: A history of stroke was more common among women in lower socioeconomic strata. The same trend was observed for the relationship between the lowest socioeconomic groups and the incidence of stroke. Risk factors for stroke were not related to socioeconomic status in a consistent manner. Smoking, history of cardiovascular diseases, and overweight were more common in lower socioeconomic groups. However, socioeconomic differences in hypertension, antihypertensive drug use, prevalence of atrial fibrillation, and prevalence of left ventricular hypertrophy were not observed. The complex of established risk factors could only partly explain the association between socioeconomic status and stroke. CONCLUSIONS: There is a strong association among elderly women between socioeconomic status and stroke. The association could only partly be explained by known risk factors. Our findings indicate that not only the actual risk profile but also risk factors earlier in life may be of importance

Iso-osmotic regulation of nitrate accumulation in lettuce (Lactuca sativa L.)

Concerns about possible health hazards arising from human consumption of lettuce and other edible vegetable crops with high concentrations of nitrate have generated demands for a greater understanding of processes involved in its uptake and accumulation in order to devise more sustainable strategies for its control. This paper evaluates a proposed iso-osmotic mechanism for the regulation of nitrate accumulation in lettuce (Lactuca sativa L.) heads. This mechanism assumes that changes in the concentrations of nitrate and all other endogenous osmotica (including anions, cations and neutral solutes) are continually adjusted in tandem to minimise differences in osmotic potential of the shoot sap during growth, with these changes occurring independently of any variations in external water potential. The hypothesis was tested using data from six new experiments, each with a single unique treatment comprising a separate combination of light intensity, N source (nitrate with or without ammonium) and nitrate concentration carried out hydroponically in a glasshouse using a butterhead lettuce variety. Repeat measurements of plant weights and estimates of all of the main soluble constituents (nitrate, potassium, calcium, magnesium, organic anions, chloride, phosphate, sulphate and soluble carbohydrates) in the shoot sap were made at intervals from about 2 weeks after transplanting until commercial maturity, and the data used to calculate changes in average osmotic potential in the shoot. Results showed that nitrate concentrations in the sap increased when average light levels were reduced by between 30 and 49 % and (to a lesser extent) when nitrate was supplied at a supra-optimal concentration, and declined with partial replacement of nitrate by ammonium in the external nutrient supply. The associated changes in the proportions of other endogenous osmotica, in combination with the adjustment of shoot water content, maintained the total solute concentrations in shoot sap approximately constant and minimised differences in osmotic potential between treatments at each sampling date. There was, however, a gradual increase in osmotic potential (ie a decline in total solute concentration) over time largely caused by increases in shoot water content associated with the physiological and morphological development of the plants. Regression analysis using normalised data (to correct for these time trends) showed that the results were consistent with a 1:1 exchange between the concentrations of nitrate and the sum of all other endogenous osmotica throughout growth, providing evidence that an iso-osmotic mechanism (incorporating both concentration and volume regulation) was involved in controlling nitrate concentrations in the shoot

Studies on the Condition for the Flower Formation in Egg Plant (7) : Relations between light intensity and day-length

この研究はナスの花成に及ぼす光の強さの影響や, 光の強さと日長の関係を確めるためにおこなった。この結果は次ぎのように要約される。1. ナスは光の強さの異なる条件の下で育てられた。光の強さは自然光と自然光の77,56,37および29%であった。この実験の結果, 光の強さがある程度以下であると, 第1花までの葉数は光の強さが減少するにつれて, やや増加する傾向があった。しかし, その違いは光の強さが異なっていても, それほど大きな差異でなく, 僅かなものに過ぎなかった。2. 温室の中で自然日長と短日, 高夜温条件の下でそれぞれ光の強さを変えて実験をおこなった。短日, 高夜温条件では光の強さはそれぞれ自然光の100,71,および54%とした。そして夜温は約21℃に調節した。自然日長条件下では光の強さは自然光の100%と54%とした。短日・高夜温条件下では光の強さが減少すると, 第1花までの葉数はやや増加する傾向であった。しかし, 自然日長下では, 光の強さは第1花の着花節位に影響を及ぼしているようにみられなかった。 / The present experiment was carried out to study the effects of light intensity and day-length for the promotion of flower formation in egg plant. Results obtained were summarized as follows : 1. Seedlings of egg plant were grown at different light intensities under natural day-length (29,37,56,77 and 100 per cent of full sunlight). When light intensities were reduced to a certain limit, a mean number of leaves formed before the first flower showed a slight increase with decreasing light intensities. 2. Seedlings were grown at different light intensities under natural (54 and 100per cent of full light) and short (54,71 and 100per cent of full light) day-length in the green house. In short-day condition, night temperature was maintained about 21℃ by a thermostat in the electric bed. Under short day-length (high night temperature) the number of leaves to the first flower increased slightly as compared with under natural day-length. The number of leaves to the first flower decreased somewhat at high light intensity under short day-length, but under natural day-length it was not affected by light intensities