Internode length in Pisum sativum L. The kinetics of growth and [3H]gibberellin A20 metabolism in genotype na Le

Abstract

The relationship between shoot growth and [(3)H]gibberellin A20 (GA20) metabolism was investigated in the GA-deficient genotype of peas, na Le. [17-(13)C, (3)H2]gibberellin A20 was applied to the shoot apex and its metabolic fate examined by gas chromatographic-mass spectrometric analysis of extracts of the shoot and root tissues. As reported before, [(13)C, (3)H2]GA1, [(13)C, (3)H2]GA8 and [(13)C, (3)H2]GA29 constituted the major metabolites of [(13)C, (3)H2]GA20 present in the shoot. None of these GAs showed any dilution by endogenous (12)C-material. [(13)C, (3)H2]GA29-catabolite was also a prominent metabolite in the shoot tissue but showed pronounced isotope dilution probably due to carry-over of endogenous [(12)C]GA29-catabolite from the mature seed. In marked contrast to the shoot tissue, the two major metabolites present in the roots were identified as [(13)C, (3)H2]GA8-catabolite and [(13)C, (3)H2]GA29-catabolite. Both of these compounds showed strong dilution by endogenous (12)C-material. Only low levels of [(13)C, (3)H2]GA1, [(13)C, (3)H2]GA8, [(13)C, (3)H2]GA20 and [(13)C, (3)H2]GA29 accumulated in the roots. It is suggested that compartmentation of GA-catabolism may occur in the root tissue in an analogous manner to that shown in the testa of developing seeds. Changes in the levels of [1β,3α-(3)H2]GA20 metabolites over 10 d following application of the substrate to the shoot apex of genotype na Le confirmed the accumulation of [(3)H]GA-catabolites in the root tissues. No evidence was obtained for catabolic loss of [(3)H]GA20 by complete oxidation or conversion to a methanol-inextractable form. The results indicate that the root system may play an important role in the regulation of biologically active GA levels in the developing shoot of Na genotypes of peas.

Ontogenetic variation in levels of gibberellin A1 in Pisum

“…types, previous information on ontogenetic and spatial variation in GA levels in this species is limited (Ingram et al 1985;Potts 1986). The present paper addresses the first deficiency and indicates a role for GA~ in regulating some aspects of the ontogenetic variation in internode elongation in wild-type plants.…”

Internode length in Pisum. Two further mutants, lh and ls, with reduced gibberellin synthesis, and a gibberellin insensitive mutant, lk

“…Plants were grown in pots in a 1:1 mixture of vermiculite and doledte chips topped with 2-3 cm of potting mix and were watered with a nutrient solution twice a week (Potts et al 1985). Data were collected from main shoots only; lateral branches were regularly removed.…”

“…Extraction and bitiassa)' of gibberellins Details of the material harvested for extraction of gibberellins are listed in Tab. 1 and follow the procedure used by Potts et al (1985). Gibbereliin extracts for the Lhllk and Lkllk comparisons were prepared as described in Potts et al (1985).…”

“…For example, Le controls the 3^-hydroxylation of GAjo to the highly active GA, (Potts et al 1982, Ingram et al 1983,1984 resulting in the tall phenotype (Mendel 1866), while na blocks an early step in the biosynthetic pathway Reid 1983, Ingram et al 1984) resulting in the extremely short nana phenotype (Wellensiek 1969). Genes La and Cry appear to be involved in the reception of the gibberellio signal (Potts et al 1985) and the gene combination la erf results in the extremely long slender phenotype (de Haan 1927). In contrast, lm may not be involved directly with the gibberellins but rather acts throngh some other aspect of cell development to produee the micro phenotype (Liodqvist 1951).…”

“…Since four of the five presently examined internode length loci appear to exert their effect through some aspect of gibberellin metabolism or sensitivity, it was considered necessary to examine whether a prima facie case exists for the involvement of these newly recognised genes with the gibberellins. For example, if they influence gibberellin biosynthesis, addition of the native biologically active gibberellio, GA, Reid 1983, Ingram et al 1983), to the mutants should result in the production of phenocopies of wild-type tall plants and levels of at least certain of the endogeootis gibberellins might be expected to be reduced. Other physiological attributes of these genes such as their graft transnussibility and action in complete darkness were also examined.…”