THE EFFECT OF KINETIN ON THE DEVELOPMENT OF ROOTS

The well-known fact that kinetin, when applied to leaves, inhibitsor completely prevents the regeneration and growth of rootsespecially of leaf-cuttings is attributed to the capacity ofkinetin to inhibit the migration of amino acids and other substances from the leaf-blades. This effect of kinetin manifestsitself also in relation to auxin. It was thus inferred thatkinetin plays an important role in those systems which decisivelyinfluence the correlations between the organs. (Received March 15, 1961; )     

ABSCISIC ACID EFFECTS ON FRONDS AND ROOTS OF LEMNA MINOR L.

Plants of Lemna minor L. were grown in axenic culture in order to investigate the direct effect of abscisic acid (ABA) on individual fronds and roots. Both frond and root growth rates were inhibited by 60%, and total growth of both organs was reduced by 30% with ABA concentrations of 2 mg/l. Abscisic acid inhibited frond reproduction, and treated fronds tended to remain attached to parents. Reduction of root elongation and frond expansion occurred within 1–4 hr. Prolonged exposure to ABA inhibited both cell enlargement and cell division in the roots. The results are discussed in the light of current views on the control of growth with endogenous levels of promoter and inhibitor hormones.     

LONGITUDINAL GRADIENTS OF ION TRANSPORT IN CORN ROOTS

Excised roots of corn, 8 cm long, were mounted for collection of xylem exudate, submerged in aerated, labeled salt solutions, and left while steady-state exudation developed. After 19 hr, additional portions of the roots were removed and all apical ends which had been severed were sealed with wax. Collection of exudate samples began 1 hr later and continued for 8 hr. The results showed that removal of only 1 cm from the apex of the root reduced the output of rubidium to the exudate by as much as 74%. They also showed that the longitudinal changes in ion contribution to the exudate were not linear, but were closely correlated with the longitudinal gradient of Rb content in the root.     

THE EFFECTS OF KINETIN AND NAPHTHALENEACETIC ACID ON IN VITRO SHOOT MULTIPLICATION AND ROOTING IN THE FISHTAIL FERN

This study is concerned with the determination of the shoot and root inducing effects of kinetin (K) and naphthaleneacetic acid (NAA) on shoots ofthe fishtail fern (Nephrolepisfalcata formafurcans) in sterile tissue culture. The data shows that K is the major factor involved in maximal shoot production. The NAA is not essential. Specific concentrations ofNAA must be present with specific concentrations of K for maximal root production. At the same time, the data also demonstrate that shoots on media containing no NAA but with K concentrations of 5 × 10⁻⁷ and 10⁻⁶ M produced as many roots as with any other NAA concentration. The data can be used as a guide to rapid commercial propagation of fishtail fern, and demonstrate that media available commercially for Boston fern multiplication will induce maximal shoot production in fishtail fern.     

THE EFFECTS OF GIBBERELLIC ACID AND KINETIN ON THE GROWTH OF MAJESTIC POTATO

The effects of spraying potato plants (var. Majestic) with gibberellic acid and kinetin were investigated. Gibberellic acid increased both leaf area and dry-matter production over the short period of the experiment, but there were indications that this would not persist at maturity. Kinetin alone depressed leaf area and dry-matter production, but this did not occur in the presence of gibberellic acid. The mean net assimilation rate measured over a 2-week period was not significantly reduced by gibberellic acid.     

CHLOROPHYLL FORMATION IN ISOLATED PUMPKIN COTYLEDONS IN THE PRESENCE OF KINETIN AND CHLORAMPHENICOL

Investigations have been made on the changes in the levels ofprotochlorophyll, chlorophyll a and chlorophyll b in relationto the kinetin induced expansion of isolated pumpkin cotyledonsin the presence and absence of chloramphenicol. It has been shown that rise in pigment level keeps pace withexpansion growth of the cotyledons. Kinetin markedly promotes the synthesis of protochlorphyll withoutmuch affecting the rate of its photoreduction to chlorophyll. Chloramphenicol strongly inhibits the development of both chlorophylla and b. The inhibition seems to be due to its interferenceboth with the synthesis of protochlorophyll and its subsequentconversion to chlorophyll. The inhibitory effect of chloramphenicol on the formation ofchlorophyll a is greater than on that of chlorophyll b, suggestingthereby the probability of divergent pathways for the formationof the two chlorophylls. (Received December 21, 1966; )