Potassium Deficiency and Excess in Guayule I. Growth Responses and Mineral Content

Abstract

The extensive literature dealing with the role of potassium in plant metabolism has been reviewed by HOFFER (20), by various authors (47) in a recent symposium and in several reviews on mineral nutrition of plants (11,17,18,28,39,46). Very recently SIDERIS and YOUNG (42,43,44) have dealt with several aspects of the problem. HOAGLAND (19) has pointed out that at one time or another a role in almost every important physiological process in the plant has been ascribed to potassium. Yet, the mechanism of its role in any specific process has not been elucidated.In several respects the guayule plant, Parthenium argentatum A. Gray, differs from most of the plants which have been subjected to detailed nutritional study. For example, incidence of the reproductive phase in guayule is not attended by cessation of vegetative growth nor by curtailed nutrient absorption. This behavior is contrasted with that of many annual plants, for which a period of rapid growth and mineral absorption is terminated by the reproductive phase. NIGHTINGALE et al. (31) found that a deficiency of potassium in tomato plants induced premature fruiting. The result was withdrawal of a large portion of the potassium from the vegetative parts to the fruits. RICHARDS and TEMPLEMAN (40) found that for the barley plant potassium deficiency resulted in continued tillering and failure of plants to head. The sodium content of the nutrient solutions appears to be a factor associated with the latter result (39). No effects analogous to the premature fruiting of tomato plants or to the retarded heading of barley plants are evident for guayule moderately deficient in potassiuim. The use of guayule plants in a study of potassium nutrition, therefore, has the advantage of permitting comparison between plants which are in different nutritional states, without complications of premature or delayed incidence of the reproductive phase.

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

“…Effects of different rates of potassium supply upon the growth anid mineral contents of guayule plants have been reported in a previous publication (5). It was noted that although the nutrient treatments resulted in large differences in concentrations of potassium and other cations within the plants, the total milliequivalents of cations per 100 grams of dry tissue for the whole plants was nearly the same for all treatments.…”

“…Sodium was determined in the dried leaves samples (5). In some cases, dried samples were also employed for determination of potassium.…”

“…The culture methods employed in growing the experimental plants have been described (5). Treatments designated K1, K2, and K3 comprised series 1.…”

“…It was noted that although the nutrient treatments resulted in large differences in concentrations of potassium and other cations within the plants, the total milliequivalents of cations per 100 grams of dry tissue for the whole plants was nearly the same for all treatments. In this paper are reported results from a study of the cation-anion balance in the leaves of the guayule plants previously described (5). An attempt was made to determine the effects of variations in contents of potassium and concomitant variations in contents of other cations upon the distribution of ions between soluble and insoluble fractions.…”

Effects of Potassium Deficiency and Excess Upon Certain Carbohydrate and Nitrogenous Constituents in Guayule

“…These workers have also shown that of the total free reducing sugars, the amounts of free nion-fructose sugars are always greater than the amounits of free fructose in spite of the fact that the chief reserve carbohydrates in guayule are polymers of fructose, levulins and inulin. The coniditions of the present experiment were not conducive to large accumulations of inulin, or higher polymer levulins, insofar as the experiment consisted of a phase of rapid growth.So far as the writers are aware, no detailed study has been made of the nitrogenous fractions in guayule.Effects of potassium supply upon growth responses and mineral contents of guayule plants and upon cation and inorganic and organic aniion contents of the leaves have been reported (8,9). In this paper are considered carbohydrate and nitrogenous fractions in tissues of the same plants.…”