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Role of GA 3 , GA 4 and Uniconazole‐P in Controlling Gravitropism and Tension Wood Formation in Fraxinus mandshurica Rupr. var. japonica Maxim. Seedlings
Author(s) -
Jiang Sha,
Xu Ke,
Wang YongZhou,
Ren YanPing,
Gu Song
Publication year - 2008
Publication title -
journal of integrative plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.734
H-Index - 83
eISSN - 1744-7909
pISSN - 1672-9072
DOI - 10.1111/j.1744-7909.2007.00552.x
Subject(s) - xylem , gibberellin , gravitropism , botany , gibberellic acid , fraxinus , japonica , chemistry , horticulture , biology , germination , biochemistry , gene , arabidopsis , mutant
GA 3 and GA 4 (gibberellins) play an important role in controlling gravitropism and tension wood formation in woody angiosperms. In order to improve our understanding of the role of GA 3 and GA 4 on xylem cell formation and the G‐layer, we studied the effect of GA 3 and GA 4 and uniconazole‐P, which is an inhibitor of GA biosynthesis, on tension wood formation by gravity in Fraxinus mandshurica Rupr. var. japonica Maxim. seedlings. Forty seedlings were divided into two groups; one group was placed upright and the other tilted. Each group was further divided into four sub‐groups subjected to the following treatments: 3.43 × 10 −9 μmol acetone as control, 5.78 × 10 −8 μmol gibberellic acid (GA 3 ), 6.21 × 10 −8 μmol GA 4 , and 6.86 × 10 −8 μmol uniconazole‐P. During the experimental period, GAs‐treated seedlings exhibited negative gravitropism, whereas application of uniconazole‐P inhibited negative gravitropic stem bending. GA 3 and GA 4 promoted wood fibers that possessed a gelatinous layer on the upper side, whereas uniconazole‐P inhibited wood formation but did not inhibit the differentiation of the gelatinous layer in wood fibers on the upper side. These results suggest that: (i) both the formation of gelatinous fibers and the quantity of xylem production are important for the negative gravitropism in horizontally‐positioned seedlings; (ii) GA 3 and GA 4 affect wood production more than differentiation of the gelatinous layer in wood fibers; G‐layer development may be regulated by other hormones via the indirect‐role of GA 3 and GA 4 in horizontally‐positioned F. mandshurica seedlings rather than the direct effect of GAs; and (iii) the mechanism for upward wood stem bending is different to the newly developed shoot bending in reaction to gravity in this species.