Salicylic Acid-Mediated Stress-Induced Flowering - Salicylic Acid: Plant Growth and Development - page 174

Yamaguchi et al. ( 2001 ) isolated norepinephrine and the a-ketol of octadeca-
dienoic acid (KODA), from which flower-inducing factors are derived, from
L. paucicostata. KODA was found to be induced by drought, heat or osmotic stress
conditions (Yokoyama et al. 2000 ). These results are consistent with the previous
finding that L. paucicostata has a mechanism that responds to stress and promotes
flowering. However, clarification of the relationship between these flower-pro-
moting factors and SA requires further investigation.
8 Salicylic Acid-Mediated Stress-Induced Flowering
in Arabidopsis thaliana
8.1 Stress-Induced Flowering in A. thaliana
Poor-nutrition conditions accelerated flowering of LD plant A. thaliana (Kolár and
Senková 2008). The authors suggested that this precocious flowering was due to
stress. When plants were grown in a full-strength nutrient solution for 3-5 weeks
and then transferred to a 1/10- to 1/1,000-strength media, the flowering time was
notably shortened. This effect was stronger when the stress was applied earlier and
increased with increasing dilutions. This acceleration was more pronounced in SD
than in LD conditions. The response was stronger in the wild ecotype Landsberg
erecta (Ler) than in Columbia (Col). The nutrient-deficient Ler plants formed
normal flowers and fruits with seeds.
UV-C light stress promoted flowering in A. thaliana (Martínez et al. 2004 ). UV-
C irradiation accelerated flowering in Col in a dose-dependent manner between 0
and 200 mJ cm -2 . UV-C induced the expression of the flowering gene FT and
moderately induced CONSTANS (CO) expression.
General stress leads to early flowering in A. thaliana. High-intensity light
(800 lmol m -2 s -1 ), high temperatures of 26 C, photochilling with 800 lmol
m -2 s -1 of light at 16 C or continuous light treatments lead to earlier flowering in
wild type Ler, but not in the fca1 co-2 ga1-3 triple mutant (Marín et al. 2011 ).
8.2 Involvement of SA in Stress-Induced Flowering
in A. thaliana
Similar doses of UV-C irradiation did not promote flowering in NahG transgenic
plants expressing bacterial salicylate hydroxylase, and these plants did not accu-
mulate SA because of the rapid and efficient conversion of SA to catechol. UV-C
light irradiation increased the expression of the SA-responsive PR1 gene in
wild type plants but not NahG plants. The expression of the SA induction