Internode Length in Pisum

Abstract

Internode length in light-grown peas (Pisum sativum L.) is controlled by the interaction of genes occupying at least five major loci, Le, La, Cry, Na, and Lm. The present work shows that the genes at all of the loci examined (Le, Cry, and Na) also exert an effect on internode length in plants grown in complete darkness. Preliminary results using pure lines were verified using either segregating progenies or near isogenic lines. The major cause of the differences was due to a change in the number of cells per internode rather than to an alteration of the cell length. Since the genes occupying at least two of these loci, Le and Na, have been shown to be directly involved with gibberellin metabolism, it appears that gibberellins are not only essential for elongation In the dark but are limiting for elongation in the nana (extremely short, na), dwarf (Na le), and tall (Na Le) phenotypes. These results are supported by the large inhibitory effects of AMO 1618 treatments on stem elongation in dwarf and tall lines grown in the dark and the fact that applied gibberellic acid could overcome this inhibition and greatly promote elongation in a gibberellin-deficient na line. It is clear that the internode length genes, and in particular the alleles at the Le locus, are not acting by simply controlling the sensitivity of the plant to Ught.The difference between tall (Le) and dwarf (le) varieties of peas (Pisum sativum L.) has frequently been equated with the difference between light-and dark-grown plants (e.g. 8, 9, 27). GA3 has been reported to cause elongation by overcoming both the dwarfing action of the le gene and the inhibition of growth by light (14). Further, tall and dwarf peas have been suggested by some workers to differ only when grown in the light (e.g. 5,8,27) although certain workers (15,29), using a range of pea varieties of unknown genotype, have found dwarf varieties to be slightly shorter than tall varieties even in the dark. Some workers (e.g. 3) have noted differences between the effects of GA3 applied to light-and darkgrown peas, and Vince (29) Recently, the action of five loci controlling internode length in light-grown peas has been examined (26). The genes at the Le and Na loci seem to be directly involved with aspects of gibberellin metabolism (22,24 any great extent. On the other hand, the gene na appears to inhibit some early step in the biosynthetic pathway of gibberellins and, therefore, plants with gene na (in combination with La and/or Cry) have very short internodes (normally less than 10 mm) and no detectable gibberellin-like substances were found in extracts from their shoots (22).The present study attempted to determine whether internode length in the dark is influenced by these genes or whether the action of these genes are modified in the dark. It is considered essential to determine whether the effects of these genes and the effects of light are independent since the presumed interrelationships between the processes has led to confusing and often contradictory theories on the c...

Gibberellin A1 Biosynthesis in Pisum sativum L.

“…They are consistent with observations that light-mediated inhibition of stem growth can be reversed by application of GA3 or GA, to pea plants (3,(7)(8)(9). They also reconcile apparently conflicting data (1, 1 [1][2][3][4][5][6][7][8][9][10][11][12][13]17) pertaining to the mechanism of control of GA1 3f-hydroxylase activity and GA, production in lightand dark-grown pea plants. LITERATURE …”

Use of an Acylcyclohexanedione Growth Retardant, LAB 198 999, to Determine Whether Gibberellin A20 Has Biological Activity per se in Dark-Grown Dwarf (le5839) Seedlings of Pisum sativum

“…9, that internode length equals that in etiolated seedlings of the wild-type cv Alaska (2,19). Despite these observations, Reid, using segregating Le/le populations (14) or near-isogenic lines (15) lings, although the degree of dwarfism was greater in the light than in the dark. Furthermore, when HPLC was used to examine the metabolic products of [3H]GA20 fed to Le and le seedlings in the dark and light, the biochemical expression of the le gene (measured as a reduction in the conversion of…”

“…The difference in internode elongation in light-and darkgrown pea seedlings has been described for several cultivars and genotypes (2,(8)(9)(10)14 There are two reports in the literature that the dwarf cv Progress No. 9 responded to GA20 in the dark, even though this GA elicited no growth response in red light when applied in the same manner and at the same dosages (1, 19).…”

“…The difference in internode elongation in light-and darkgrown pea seedlings has been described for several cultivars and genotypes (2,(8)(9)(10)14). Etiolation is so great in some dwarf cultivars, e.g.…”

The Gibberellin Status of lip1, a Mutant of Pea That Exhibits Light-Independent Photomorphogenesis

“…1 and 2). An increased rate of internode production is a common feature of de-etiolation (Reid, 1983;Sponsel, 1986). However, possibly the most striking visible effect of lipl in the dark was on the expansion of individual leaves.…”