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Seasonal variations in the composition of milk Texte intégral
1950
Nichols, L.E. | Few, F.G.
The chemical composition of milk from herds of various breeds on eight farms within the Brisbane milk supply area was determined at intervals over periods ranging from 12 months to 30 months. The evidence suggests that variation in milk composition is due largely to changes in the nutritive value of pastures.
Afficher plus [+] Moins [-]Specific Volume of Native Cellulose Texte intégral
1950
Stamm, Alfred J.
Specific-volume measurements of native cellulose determined in different media and calculated from x-ray data are compared. Data for the specific volume of cellulose containing different amounts of water measured in a benzene medium are analyzed. On the assumption that the differ ence between the specific volumes measured in benzene and the specific volume calculated from x-ray data is due to voids, and that the differences between the x-ray value and the values deter mined in water are due to the compacting of water, reasonable compression values are obtained that are in accord with the concept of hydrogen bonding of water and other findings.
Afficher plus [+] Moins [-]Observações citológicas em Coffea: XVII - O saco embrionário em Coffea canephora Pierre ex Froehner Texte intégral
1950
Mendes, Cândida H. T.(Instituto Agronômico de Campinas Secção de Citologia)
A study has been made of the embryo sac in self-sterile Coffea canephora flowers of different ages. The process was observed to be normal and included the formation of two synergides and one egg cell in the micropilar region, three antipodals at the chalazal region and two polar nuclei lying in the middle of the sac. It is known that in the species C. arabica the embryo sac formation is complete at the time the flowers open. Embryo sac formation in C. canephora is slightly delayed and it is not complete until the day following opening of the flowers. It was also determined that in C. canephora shedding of pollen begins shortly after the flowers open and the pollen was functional at least for two days. Thus the results of the present study indicate that the self-sterility of C. canephora flowers is not due to the delay in formation or abnormal development of the embryo sac.
Afficher plus [+] Moins [-]Plant studies with radioactive sodium Texte intégral
1950
Leonard, C.D. | Toth, S.J.
Radioactive Na22 was introduced into a series of sand and outdoor cylinder cultures to obtain supplementary information on the nutrient value of Na. The most important findings were: The absorption of Na22 was governed by the same factors that determined the uptake of Na. In sand cultures, the absorption of Na22 by plants was affected by the K and Na levels in the substrate. At constant K levels, the absorption of Na22 decreased as the Na level increased. At constant Na levels, the absorption of Na22 increased as the K level decreased. Na22 tended to concentrate in the conducting tissues of plants. This was confirmed both by activity measurements and by radioautographs. The less mature fractions of tomato plants contained the bulk of the absorbed Na22. Between 57 and 91.6% of the absorbed Na22 found to be in the sap of plants. Celery plants absorbed Na22 at a faster rate than tomato plants. Sugar beets, except those that received nitrogen in the form of calcium nitrate, obtained most of their Na22 from a 6-inch soil depth.
Afficher plus [+] Moins [-]The availability of the calcium and phosphorus in " electrofos " for bone formation. I. In the rat Texte intégral
1950
A basal diet, containing 0•06 per cent. calcium and 0•05 per cent. phosphorus, and albino rats, 4 to 5 weeks old and weighing approximately 60 grams, were used to ascertain the availability of electrofos I and electrofos II in comparison with dicalcium phosphate for bone formation. These phosphatic products, prepared by a thermal process, were studied at two levels giving diets containing 0•18 per cent. phosphorus and 0•36 per cent. phosphorus, the Ca : P ratio being maintained at about 2 : 1. Apart from live weight gains percentage retention of the relevant minerals as determined by slaughter tests and femur ash were used as criteria for evaluating the products. The averages of the results obtained are summarized in Table 18. It was found that both electrofos I and electrofos II were significantly less available for bone formation than calcium phosphate. However, more or less equal bone formation was obtained when these products were supplemented at about twice the level of calcium phosphate.
Afficher plus [+] Moins [-]De landbouwkundige grondslag van snoei en pluk bij Assamthee Texte intégral
1950
Schoorel, A.F.
From experiments the following conclusions could be drawn: The increase in diameter of the stems of free growing tea plants is practically proportional to time if the growing conditions of the shrubs do not change. However, tea plants in gardens producing tea leaf are planted so closely, that full development of the bushes is hampered. Pruning and plucking further influences the trees physiologically.Tea shoots have an alternation of periods in which leaves are formed, and periods in which the development of leaves completely stops. Every shoot has its own rhythm not necessarily coinciding with that of other shoots of the same bush. This rhythm is not autonomic but is determined by outward circumstances. The effect of plucking green leaves for the production of dried tea can be divided into influences of the kind of leaves plucked, the length of the plucking round and the kind of leaves left on the bush on the production, quality of the leaves, and physiological condition of the plant. So nine different influences can be distinguished.Over a long period tea bushes cannot stand such severe plucking that would prevent the plucking level rising. Consequently pruning periodically is essential to keep the tea plantation productive. Pruning of tea gardens is also necessary to keep the plants in a good physiological condition.
Afficher plus [+] Moins [-]The estimation of oil percentage in safflower seed and the association of oil percentage with hull and nitrogen percentages, seed size, and degree of spininess of the plant Texte intégral
1950
Claassen, C.E. | Ekdahl, W.G. | Severson, G.M.
The relationship between the oil percentage of the seed to oil percentage in kernel, hull and nitrogen percentages of seed, seed size, and degree of spininess of the plant were determined. The following statistically significant correlations were obtained: oil and hull percentage of the seed -0.77 and -0.81, oil and nitrogen percentage of seed -0.34, oil percentage of seed and seed size 0.22, oil percentage of seed and degree of spininess of plant 0.20. Oil percentage of kernel was found to be positively associated with oil percentage of whole seed and with seed size. Two methods of estimating oil percentage in seed were investigated. One method was based on a simple external examination of seed. The other method was based on general appearance of a finely crushed 2 gram sample of seed. Correlations of 0.93 and 0.90 were obtained between the estimated and actual oil percentage for the two methods, respectively. Approximately 75% of the samples were estimated within 2% of the actual oil percentage. These results show that estimation of oil percentage is of value in eliminating low oil selections before any chemical analyses are made in breeding material.
Afficher plus [+] Moins [-]De landbouwkundige grondslag van snoei en pluk bij Assamthee
1950
Schoorel, A.F.
From experiments the following conclusions could be drawn: The increase in diameter of the stems of free growing tea plants is practically proportional to time if the growing conditions of the shrubs do not change. However, tea plants in gardens producing tea leaf are planted so closely, that full development of the bushes is hampered. Pruning and plucking further influences the trees physiologically.Tea shoots have an alternation of periods in which leaves are formed, and periods in which the development of leaves completely stops. Every shoot has its own rhythm not necessarily coinciding with that of other shoots of the same bush. This rhythm is not autonomic but is determined by outward circumstances. The effect of plucking green leaves for the production of dried tea can be divided into influences of the kind of leaves plucked, the length of the plucking round and the kind of leaves left on the bush on the production, quality of the leaves, and physiological condition of the plant. So nine different influences can be distinguished.Over a long period tea bushes cannot stand such severe plucking that would prevent the plucking level rising. Consequently pruning periodically is essential to keep the tea plantation productive. Pruning of tea gardens is also necessary to keep the plants in a good physiological condition.
Afficher plus [+] Moins [-]Quantidade de água transpirada pelo cafeeiro cultivado ao sol Texte intégral
1950
Franco, Coaraci M.(Instituto Agronômico de Campinas Secção de Fisiologia e Alimentação das Plantas) | Inforzato, Romeu(Instituto Agronômico de Campinas Secção de Fisiologia e Alimentação das Plantas)
In determinations made with a porometer it was verified that the stomatal opening of coffee leaves increases in size immediately after the leaves are detached from the plant (fig. 1). This fact indicates that the method of rapid weighings of detached leaves is not suitable for studies on the transpiration of the coffee plant. The transpiration of coffee plants has been determined by the weighing potted plant method. Pots with a capacity for 51 liters were used. They were made of galvanized iron plate and had no drainage hole. When the moisture content of the soil approached the wilting point water was added to bring all the soil mass to fiel capacity. In order to avoid oxygen depletion the pots were not sealed. To decrease the direct evaporation at the soil surface a two-centimeter layer of rice hulls was used as mulch, and a celotex cover was placed on top of the pot. Three similar pots with the same type of protection, but without plants were used to measure the direct evaporation from the soil surface. The weight losses of these pots were subtracted from the weight losses of the pots with plants. Two to throe-year old plants of Coffea arabica var. bourbon were used. Three plants were employed each month and after this time their leaves were picked off, and the total leaf area was determined. The tests were carried out for a whole year. The transpiration rates were calculated in g/dm²/day. The total leaf area of an adult coffee plant was found to be 3,146 dm² (average of seven trees). Based on this average and on the transpiration rate of the experimental plants it was possible to calculate approximately the amount of water that an adult coffee plant would transpire under the same conditions. Since the plants submitted to the experiment did not suffer water shortage at any time, the present results show the approximate amount of water lost by the coffee plant under optimal soil-water conditions. The data are presented in table 1. The figure 1 shows the monthly amount of water lost by transpiration in a coffee* plantation compared with the monthly rainfall during a year. The environmental factors that influence plant transpiration vary much less between the same months of different years than between the different months of the same year. Hence the results obtained should not be far from the average; that would be obtained if the transpiration had been measured during a number of years. Comparing the water lost by transpiration of coffee trees with the average rainfall in'Campinas, State of São Paulo, Brazil, it is seen that from October to March rainfall exceeds water consumption. In April, June, and September the excess is small, and in May, July, and August the amount of water transpired exceeds the average rainfall (fig. 2). Since the rainfall distribution is variable, this figure may be different in a given year. The highest daily rate of transpiration encountered was 17.6 mg/dm²/m (over twelve; hours). Previous results obtained by the writers showed 18.2 mg/dm²/m to be the rate of transpiration in a very sunny and hot day. Nutman working in Africa (2) found a maximum daily rate of 20.67/dm²/m (over nine hours). These data are comparable and must represent approximately the maximum rate of transpiration of the coffee plant. The average daily transpiration encountered was 6.20 g/dm²/day and the total amount of water transpired by a coffee tree in one year was found to be 7,273 liters.
Afficher plus [+] Moins [-]Xenia effects of irradiating corn pollen in a nuclear reactor Texte intégral
1950
Frolik, E.F. | Morris, R.
Xenia effects in corn crosses involving tassels irradiated in a nuclear reactor were determined in comparison with crosses involving X-rayed and non-irradiated tassels. Irradiations were made in the thermal neutron column of the heavy water pile at the Argonne National Laboratory for periods of 1/2, 1, 2, 4, 8, and 16 minutes, respectively. The X-ray dosage consisted of 1200 r units. In general, the percentage of entire mutations increased with increase in length of time of exposure in the nuclear reactor. The effectiveness of pile radiation varied markedly with date of treatment. There was considerable uniformity in the response of individual plants to comparable irradiation treatments. The effectiveness of X-ray treatment varied somewhere between 1/2 minute and 4 minutes of pile irradiation, depending on date of treatment and on the character involved. The percentage of mutations for both sources of radiation varied for the characters under study in the following decreasing order of frequency: (a) defective kernels, (b) colorless aleurone, (c) sugary endosperm, and (d) red aleurone. The frequency of chimeras was affected far less than that of entire mutations by the pile radiations. No association was apparent between frequency of recoveries and either pile radiation or X radiation. No qualitative differences between the two types of radiation were noted in these tests.
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