Some Physico-Chemical Effects of Organic Soil Colloids

An investigation was undertaken to determine the reason for injurious effects of lime to grains grown on certain acid organic soils which occur in the Great Lakes region. Analyses were made of the soils (table I) and crops (table II) in order to determine if a harmful physical change occurred in the soils after liming or if lime was chemically injurious. The organic soils studied were black, powdery, acid and deficient in potash as shown by the soil analyses. Crop injury following use of lime to correct acidity in these soils is an unexpected response which occurs frequently enough to justify investigation

Nutritional Factors in Plant Growth and Development - Paper Presented at the Fifty-Sixth Annual Meeting

The large number of recent publications on the physiology of plant development reflects a widespread, contemporary interest in this subject. Researches in this area deal chiefly with the effects of specific growth substances and mineral nutrients on functional and structural ontogeny. The major contributions on the physiology of growth substances have already been conveniently assembled in certain excellent monographs (36, 53, 283, 339, 424) and reviews (37, 422, 192). Recent researches on nutrition in relation to plant development have not as yet been comprehensively reviewed. Data in this field as a whole are extremely diverse, especially as they relate to the nutritional cycle of biennial and perennial crops (20, 259, 411). In typical annuals, however, certain common relationships seem to characterize the mineral, carbohydrate and protein metabolism such that a number o

Sap Hydrion Concentration as a Factor in Plant Metabolism

In poorly drained humid portions of the glacial drift area of the eastern half of the United States occur certain unproductive organic soils which superficially resemble fertile loams. Analyses of these unproductive types generally disclose high acidity and mineral deficiency, especially of potassium. In many instances, however, lime employed to correct acidity, and potash to increase the nutrient value of the soil have proven injurious instead of beneficial to grain crops. The present investigation was undertaken to determine the explanation of the anomalous response and the exact nature of the injury

The Effect of Light Intensity on Tissue Fluids in Wheat

Foliar chlorosis was observed to occur frequently during periods of strong insolation in grain plants growing humus soils to which lime had been added to correct acidity. An experiment was undertaken to determine the reasons for the increasing prevalence of chlorosis during periods of clear, sunny weather

Studies of the Diurnal Fluctuations of Sap Hydrion Concentration in Young Wheat Plants

Diurnal fluctuations in the acidity of tissue fluids in six to ten week old wheat plants were followed by potentiometric pH measurements of sap freshly expressed from plants at various hours of the day. A daily average fluctuation of 1.5 pH was observed in young plants. The range of pH variation was appreciably extended by increased illumination, maximum acidity occurring dur- ing the early hours of daylight and thereafter falling steadily until the minimum was attained several hours after dark. This degree of pH fluctuation is correlated with variations in the osmotic pressure of expressed sap and thus important in modifying the solubility of nutrients

Effects of Soil Aeration on Plant Growth and Root Development

Considerable is known concerning the immediate effect on root growth of excess carbon dioxide and shortage of oxygen in the soil. The ecologic importance of soil atmosphere in relation to root growth has also been studied. Very little work has been done on the formative and metabolic effects of continuous liberal soil aeration on plants so grown. A preliminary report is herewith presented of the formative effects of optimal air supply upon root and top growth in several types of plants whose roots differ in their oxygen requirements

Preliminary Report on Amino Acid Synthesis in Plants

The process of amino acid synthesis in plants involves essentially a reduction of nitrates absorbed from the soil. It is difficult, however, to distinguish newly synthesized amino acids from those originating as hydrolytic cleavage products of proteins. To circumvent this difficulty, earlier investigators (2, 5, 6, 8), exposed their plants to nitrogen starvation, thereby reducing soluble nitrogen compounds in tissues to a minimum. Unfortunately, it is extremely difficult to remove final traces of nitrates and ammonia by starvation without causing high mortality in experimental material, and pathological conditions in many of the plants which do survive this rigorous treatment

The Teaching of Botany - Appraisal and Forecast

In undertaking a discussion of biology in education it is highly desirable to view the subject against the general background of American education as a whole. Among the nations of the world, the United States possesses the unique distinction of having mass education. We owe this policy to the shrewd foresight of the fathers of the American Revolution, to their recognition of the fact that the success of representative government depends upon an enlightened electorate. As an object of primary importance, George Washington enjoined the new nation to promote institutions for the general diffusion of knowledge. In his first inaugural address he stated that as government gives force to public opinion, it is essential that public opinion should be enlightened. Though we as individuals commonly regard education as a means of improving our economic status, American statesmen have never lost sight of its greater importance in making democracy feasible. Because the civic value of education far transcends its benefits to the individual student, a system of free public was established and the education made compulsory

Water and Salt Balance in the Growth of Annual Plants (Abstract)

The report deals with the far-reaching and critical shifts in water and salt content which occur during the flowering phase of development in such annuals as hemp, beans, corn and wheat. This phase is marked by a sudden increase in transpirational water loss and the coincident diminution in the rate of water and salt absorption by the roots. Though the progressive tissue dehydration results in the increase of the osmotic solutes in the cell sap, the resultant rise in osmotic pressure does not serve to prevent continued water loss. This stage is also marked by appreciable hydrolysis of the insoluble carbohydrates and proteins in the leaves, as well as by a profound redistribution of mineral elements within the entire plant. The data suggest that some of these changes are concerned with the inception of flower primordia and to some extent determine the number of flowers developed and fruits which set. The flowering phase, though of brief duration, is the most significant in determining the subsequent development of the entire plant. The nutritional physiology of the flowering phase is distinctly different from that of the preceding vegetative and the subsequent fruiting physiology

Nutritional Physiology of Certain Dioecious Plants

Further study has been made of the metabolic expression of sex in shoots of typical dioecious hemp plants. Results obtained show significant differences in metabolism of corresponding shoot regions of the two sexes before as well as after the development of sexual dimorphism