Annals of Botany 61: 331-345, 1988
© 1988 Annals of Botany Company
RESEARCH-ARTICLE |
Internode Length in Pisum: Variation in Response to a Daylength Extension with Incandescent Light
Botany Department, University of Tasmania Hobart, Tasmania 7001, Australia
Accepted: 6 November 1987
Lines representing a range of internode length and flowering genotypes in Pisum sativum L. were grown in 8 h of daylight followed by either 16 h of darkness or incandescent light. The stem elongation response index (RI = length in 24 h ÷ length in 8 h) was least in the very short internode nana types, which are grossly deficient in gibberellins (GAs), and the very long internode slender types, which behave as if saturated with GAs. The common tall (genotype Le) and dwarf (le) types (le partially blocks conversion of GA20 to the active form, GA1) were all markedly responsive but the peak RI (based on the most responsive internode) was less in tall lines (1.79 to 2.78) than in dwarf lines (2.32 to 5.01) and the peak RI tended to occur about three to four internodes earlier in tall than in dwarf lines. The cry8 mutation reduced the RI. (Duplicate length loci La and Cry are probably concerned with GA reception.) Among le dwarf lines, genotype La cry8, was generally less responsive than La Cry, La cryc and la Cry. Data from crosses showed that on either an le La or le la background cry8 segregates had a lower RI than cry8 segregates. On an le la background, cry8 plants were shorter than cryc plants, cry8 was partially dominant to cry8 and segregation was clear only in long days. On an le la background, cryc plants were shorter than cryc plants, cry8 was partially dominant to cry8 and segregation was clear in long or short days. The very high peak RI (5.0) of the microcryptodwarf line, L57, appeared to result, in part, from a marked foreshortening of internodes 4 to 10 in the 8 h regime. In the 24 h regime L57 (lm) had a fairly similar growth pattern to normal (Lm) cryptodwarf types.
The peak RI tended to occur at a lower internode in early than late flowering lines, especially among dwarf types, and genotypes with a day neutral flowering habit (genotype sn or dne) were less responsive than their photoperiodic counterparts (Sn Dne).
White fluorescent light, given as a daylength extension, was much less effective than incandescent light at stimulating stem elongation suggesting control through the phytochrome equilibrium (Ptr/Ptotal).
Pisum sativum, garden pea, daylength extension, flowering, genotype, gibberellin, hormone receptor, incandescent light, internode length, phytochrome, stem elongation