Determination of Root Exudates in a Steril Continuous Flow Culture. II. Short-Term and Long-Term Variations of Exudation Intensity

Abstract

Abstract. The exudate production of alfalfa under the conditions of the sterile flow culture was quantitatively measured. In the first 40 days 3.10-3 ,mmoles amino-N, 2.5 ,,uequivailents of organic acids and approximately l04 ,moles of reducing sugars were liberated per plant and per day into the percolating nutrient solution. The amino acid concentration in the outflow varies according to a daily periodicity. The exudation of a colored substance also shows daily periodical variations. This pattern is d6ifferent from the pattern of the amino acid exudation, however, and directly coupled to -shoot illumination. Short-term 2,4-dinitrophen,ol additions to the nutrient lower the liberation of amino acids into the percolating soilution.Much work has been done to learn more about the special conditions and processes which characterize the plant root rhizosphere. Some literature reviews concerning root exudates were published since 1964, considering the more general character (32,33) as well a's the special aspects of the subject (2, 7). Several papers presenting quantitative and semi-(Iuantitative data on exudate production were the background for the experiments and results here to be described.

Temperature effects on root nodule activity and nitrogen release in some sub-tropical and temperate legumes

“…The increase in N exudation at a high temperature (35~ (Table 6) may also be attributed to the increase in root metabolic activities or changes in the membrane permeability. This assumption is supported by the fact that, in soybean and sesbania, N exudation per unit root dry weight was higher at 35~ than at 15 and 25~ (Table 6b), while in chinese milk vetch, N exudation per unit root weight was highest at 15~ Richter et al (1968) observed that the depression of the respiration rate induced by the respiratory poison, dinitrophenol attenuated the loss of some amino acids, suggesting the presence of a correlation between root exudation and metabolism.…”

Influence of Age and Stage of Development on the Neutral Carbohydrate Components in Root Exudates From Alfalfa Plants Grown in a Gnotobiotic Environment

“…Root exudates of corn (Zea mays L.) were analyzed after 8 and 16 days' growth for changes in carbohydrate composition by Arkadeva (1963a (Smith and Peterson 1966). Richter et al (1968) (Arkadeva 1963b;Balasubramanian and Rangaswami 1969;Rovira I956q;Rovira 1959;Schreiber and Green 1963 (Adams et al 1968;Schroth et al 1963;Smith and Peterson 1966 Jones (1943) has reported that the grand period of growth for transient or no{r-cambial roots of alfalfa ends with the onset of flowering and is followed by a period of inactivity and root disintegration. It has been suggested that the development of flower primordia in grasses has a deleterious effect on root development (Stucky 1941 …”

Herbage Characteristics of Pintoi Peanut and Paslisadegrass Established as Monoculture or Mixed Swards

“…by the association Rhizobium and legumes can be transferred to forage grass species through different pathways, including exudation, senescence, and degradation or direct transfer of N from legume to non-legume roots (Richter et al, 1968). Despite the vast body of literature indicating the benefits associated with legumes in mixed swards, widespread utilization of tropical legumes worldwide is still scarce.…”

“…by the association Rhizobium and legumes can be transferred to forage grass species through different pathways, including exudation, senescence, and degradation or direct transfer of N from legume to non-legume roots (Richter et al, 1968).…”