The influence of the Na and Le genes in peas on gibberellin (GA) levels and metabolism were examined by gas chromatographic-mass spectrometric analysis of extracts from a range of stem-length genotypes fed with [13C, 3H]GA20. The substrate was metabolised to [13C, 3H]GA1, [13C, 3H]GA8 and [13C, 3H]GA29 in the immature, expanding apical tissue of all genotypes carrying Le. In contrast, [13C, 3H]GA29 and, in one line, [13C, 3H]GA29-catabolite, were the only products detected in plants homozygous for the le gene. These results confirm that the Le gene in peas controls the 3β-hydroxylation of GA20 to GA1. Qualitatively the same results were obtained irrespective of the genotype at the Na locus. In all Na lines the [13C, 3H]GA20 metabolites were considerably diluted by endogenous [12C]GAs, implying that the metabolism of [13C, 3H]GA20 mirrored that of endogenous [12C]GA20. In contrast, the [13C, 3H]GA20 metabolites in na lines showed no dilution with [12C]GAs, confirming that the na mutation prevents the production of C19-GAs. Estimates of the levels of endogenous GAs in the apical tissues of Na lines, made from the 12C:13C isotope ratios and the radioactivity recovered in respective metabolites, varied between 7 and 40 ng of each GA per plant in the tissue expanded during the 5 d between treatment with [13C, 3H]GA20 and extraction. No [12C]GA1 and only traces of [12C]GA8 (in one line) were detected in the two Na le lines examined. These results are discussed in relation to recent observations on dwarfism in rice and maize.

Internode length in Pisum

Substances potentially involved in allelopathy are liberated from plants by (a) leaching of foliage by rain, (b) abscission and litter fall, (c) volatilization from foliage, and (d) root exudation. Substances, including metabolites such as mineral nutrients, carbohydrates, amino and organic acids, and growth regulators, can be leached from a wide variety of plants by rain and dew, and the quantity and quality of losses are affected by a great number of both external and internal factors. Materials leached from one plant may have an influence upon the development of the same or other adjacent plants. Plant/plant chemical interactions have been well recognized in commercial agriculture and, in fact, form the basis of many common agricultural practices. They are currently being utilized in modern plant science in the development of bioassay systems for detecting growth regulators, the use of rootstocks to influence the growth and development of scions, in detection and eradication of diseases, and in fruit storage and ripening.

Implications of allelopathy in agricultural plant science

A new, elongated mutant of garden pea (Pisum sativum L.) is described, and shown to be conferred by a recessive allele of a new gene, sln. At the seedling stage, the mutant resembles the previously described slender type (genotype la cry (s) ), possessing markedly longer basal internodes than the wild-type. Furthermore, as for la cry (s) plants, application of gibberellin (GA)-biosynthesis inhibitors to the dry seeds (before sowing) did not markedly affect internode length in the mutant. However, the inheritance of the new slender phenotype is unusual, since in crosses between sln and Sln plants the mutant phenotype is absent in the F2 generation, reappearing in the F3. Young shoots possessing the new slender phenotype (sln) contained much higher levels of GA1, GA8, GA20 and GA29 than did wild-type shoots. Mature, near-dry seeds from slender plants contained very high levels of GA20, marginally more GA29, and very little (if any) GA29-catabolite, compared with seeds harvested from wild-type (Sln-) plants. It is suggested that sln may impair the catabolism of GA20 in maturing seeds. As a result, GA20 accumulates and on germination may move into the seedling where it is converted to GA1, promoting elongation growth. A model is proposed to explain the inheritance of the sln phenotype and its physiological implications are discussed. The new sln slender mutation has a different mode of action from the established la cry (s) slender gene combination.

Internode length in Pisum : A new, slender mutant with elevated levels of C19 gibberellins.

Gibberelline : XLIII. Mitt. Fraktionierung von Gibberellinen, Gibberellinkonjugaten und anderen Phytohormonen durch DEAE-Sephadex-Chromatographie☆☆☆

In developing apical meristems of corn, the level of acidic, ethyl acetate-soluble gibberellin (GA)-like substances increased to a maximum of 108 micrograms GA(3)-equivalents per kilogram dry weight of tissue at inflorescence initiation, and then fell rapidly. At anthesis, only a trace (0.2 microgram per kilogram) of GA-like activity remained in the apical (male) inflorescences, whereas moderate activity (32 micrograms per kilogram), mostly of a nonpolar nature, was present in lateral, female, inflorescences.A sex reversal of the apical inflorescence, from male to female, was elicited by reducing the ambient light intensity. Higher levels of GA-like substances, particularly those eluting from a SiO(2) partition column in the nonpolar region, were observed at all harvests in the reverting meristems; levels increased to 180 micrograms per kilogram at inflorescence initiation, then dropped to 122 micrograms per kilogram in the apical (female), reverted meristems. This increase in endogenous GA-like activity with reversion to the female inflorescence is consistent with observations that (a) reversion can be obtained with exogenous application of GA(3) and (b) maleness is enhanced in GA-deficient mutants of maize. Endogenous GAs may thus play a key role in the control of sexuality of corn.

Changes of Endogenous Gibberellin-like Substances with Sex Reversal of the Apical Inflorescence of Corn.

ALTHOUGH there are many chromatographic methods for separating the various gibberellins from each other, there appears to be no report of the use of silica gel partition columns. Columns are more useful for preparative separations than thin layer and paper chromatographic methods. Methods using absorption columns made with charcoal and silicic acid have been described1,2. Partition columns are usually considered to provide especially mild conditions for chromatography, which may be important with compounds that tend to be somewhat labile, such as the gibberellins.

Kestutis J. Tautvydas

Papers

Chromatography of Gibberellins on Silica Gel Partition Columns