Plant buffer systems in relation to the absorption of bases by plants

Orange fruits undergo certain definite and progressive changes in chemical composition during growth and maturation. The rates at which these changes occur depend chieflv upon climatic and soil conditions, but they are also somewhat affected by the rootstock, as shown by HODGSON and EGGERS (15), SINCLAIR and BARTHOLOMEW (17), and others. While studying the influence of rootstocks on the composition of citrus fruits, it seemed important to the authors to investigate the changes that occur in the soluble constituents of the juice during growth and maturity of the fruit, and, especially, to correlate the concentration of one soluble constituent with that of another for the purpose of determining their physiological and biochemical characteristics. The present studies were therefore undertaken.It is well known that differences in the composition of citrus fruits are due not only to variety and similar factors, but also to the influence of the geographical location in which the fruits are grown, and to seasonal changes affecting the rate of the ripening processes. A study of the effects of these environmental factors on the composition and quality of the fruit has clearly demonstrated that, without actual investigation, it is not safe to conclude that the characteristics of the citrus fruits in one locality are the same as those of the fruits in another locality. For this reason it is of extreme importance to know the changes in soluble solids, total and reducing sugars, acids, and pH that occur during the growth and maturity of citrus fruits in the different citrus-growing areas of southern California. A knowledge of the interrelation of these particular constituents has served as a foundation upon which a more extended and specialized program of research on citrus fruits has been initiated.The results reported in the first part of the present paper, which concerns the interrelation of juice constituents, are especially significant because they show the combined effects of different rootstocks, soils, and regional and annual climatic factors on the constituents of orange juice, over a period of several years. Data presented later in the paper show the effect of external factors and of some of the juice constituents on the buffer properties of the juice.

Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 74%

Soluble Constituents and Buffer Properties of Orange Juice

Bartholomew

Sinclair

1943

“…265-291) for a discussion of the buffering of potato sap between the limits pH 4.5 to 7.0. DUNNE (8) has utilized this method of approach in connection with problems of mineral nutrition, and HOAGLAND and his collaborators have freely utilized it as an indirect means of investigating the chemical changes which accompany the uptake of salt in barley roots. The authors were familiar with the latter investigations and hence applied this technique in the case of potato discs.…”

Section: Titration Curves Of Potato Sapmentioning

confidence: 99%

Metabolic Processes of Potato Discs Under Conditions Conducive to Salt Accumulation

Steward

Preston

1940

IntroductionModern inivestigations (11, 34) show that vital activity plays an essential part in salt acetmulationi by planits. The ability to accumulate2 demands properties peculiar to cells which are still able to grow and the rate at which these are utilized is causally related to the intensity of aerobic respiration. Salt accumulation is not merely the result of equilibria at membrane surfaces but demands some "dynamic machinery" in cells-to use a happy phrase which received prominence in a recent symposium. A similar concept is implied by the oft repeated assertion that during salt accumulation work is done and energy exchanges are involved. The identification of the "dynamic machinery" and the mechanism by which the energy stored in substances of high energy content is ultimately utilized in salt accumulation is one of the most challenging problems of modern plant physiology.The earlier work, done on Nitella, Elodea, discs cut from storage organs, and roots, focussed attention upon those biochemical processes in the accumulating cells which involve carbohydrates and suggested that these represent an important part of the machinery of accumulation. In a brief review of available evidence (33) it was concluded that the biochemistry of salt absorption represented a virgin field for investigation and this inspired much of the work to be described in this and ensuing papers.The relationship between salt accumulation and metabolism has been most investigated with reference to respiration as measured by carbon dioxide output. The conclusion to be drawn (11,33, 34) is that the relation between salt uptake and respiration is not a simple and direct one; it concerns the aerobic phases of the respiratory process but it is the oxidation which these involve, rather than the production of carbon dioxide per se, which is causally concerned in salt accumulation. The ultimate connection between respiration and salt accumulation must therefore involve some aspect of the oxidative breakdown of sugar-the ultimate source of carbon substrates-other than the mere evolution of the carbon dioxide which is finally produced. The energy thus released must be involved; not only because it supplies the relatively small amount of energy necessary for the actual process of salt uptake, (a process which tends to increase the free 'This is the first of a group of papers on the biochemistry of salt absorption. 2 Especially that most general type of accumulation which involves the simultaneous uptake of anion and cation and which has been termed "primary absorption." Certain absorption processes in which metabolism is not involved are not in question here. PLANT PHYSIOLOGY energy of the system concerned) but also because it maintains the cells at that general level of metabolic activity which is an invariable characteristic of systems capable of a high degree of salt accumulation. Hence the biochemistry of salt accumulation entails an account of the fate of the carbohydrates metabolized during salt accumulation-an account which must ultimat...

“…This result is analogous to results obtained by ULRICH (33) in that an increase in soluble cations in excess of soluble inorganic anions was associated with an increase in organic acids. DUNNE (8)found that wheat and buckwheat plants supplied with low calcium solutions had higher values for the excess of soluble cations. The sap from these plants showed increased buffering in the acid range, iildicating higher organic acid content.…”

mentioning

confidence: 99%

Potassium Deficiency and Excess in Guayule. Ii. Cation-Anion Balance in the Leaves

Cooil

1948

In many plants the potassium contained in the tissues is almost completely water soluble (3,15,16, 18, 19,32) It is generally supposed that much of the potassium present in plants is in the form of salts of organic acids and that these acids and their salts constitute principal components of the buffer systems. A relationship between the total organic acids and the excess of cations over inorganic anions in tobacco leaves of different ages and base composition was shown by PUCHER, VICKERY, and WAKEMAN (22). PIERCE and APPLEMAN (21) grew several species of plants in the same nutrient medium and showed a general correlation between the excess of cations and the total organic acids. In these correlations, however, were ineluded both soluble and insoluble constituents, and variations in insoluble oxalate and calcium contributed much to the variations in the total bases and organic acids. ULRICH (33) has shown that the total organic acid content of sap expressed from barley roots may be varied by unequal absorption of cations and anions from the solution. An absorption of cations in excess of anions results in an in-