IN-VITRO MORPHOGENIC CHARACTERISTICS OF PHYTOCHROME MUTANTS IN NICOTIANA-PLUMBAGINIFOLIA ARE MODIFIED AND CORRELATED TO HIGH INDOLE-3-ACETIC-ACID LEVELS
Y. Kraepiel et al., IN-VITRO MORPHOGENIC CHARACTERISTICS OF PHYTOCHROME MUTANTS IN NICOTIANA-PLUMBAGINIFOLIA ARE MODIFIED AND CORRELATED TO HIGH INDOLE-3-ACETIC-ACID LEVELS, Planta, 197(1), 1995, pp. 142-146
The involvement of indole-3-acetic acid (IAA) in the integration of th
e light signal perceived by phytochrome during the morphogenesis of pl
ants was investigated in Nicotiana plumbaginifolia Viviani. The chromo
phore mutant pew1, deficient in all the phytochrome types, and the aur
ea-like mutant pew2, which appears to be specifically deficient in phy
tochromes expressed in darkness, were analysed for IAA-related morphog
enic effects such as rooting, shooting and callus formation. We observ
ed, in the absence of exogenously applied hormones, abundant root form
ation by the pew2 mutant. The pew1 mutant exhibited callus formation i
n the presence of gibberellins and cytokinins when the wild type did n
ot. The previously described lethality of the double mutant pew1-pew2
was shown to be hormone-dependent since, in the light, exogenously app
lied auxin and cytokinin (0.1 mg . 1(-1) each) led to plant regenerati
on from calli and subsequent normal development. These observations su
ggested an increase in the auxin/cytokinin ratio as a consequence of t
he phytochrome mutations. We correlated these morphogenic characterist
ics with high IAA levels in the mutants. The difference in IAA accumul
ation in the two mutants indicates that among the different phytochrom
es expressed by N. plumbaginifolia, the light-expressed isoforms play
a major role in the control of IAA levels.