title: Abscisic acid substantially inhibits senescence of cucumber plants (Cucumis sativus) grown under low nitrogen conditions.
abstract: Low nitrogen (N) availability such as that found in both dry land and tropical regions limits plant growth and development. The relationship between the level of abscisic acid (ABA) in a plant and its growth under low-N conditions was investigated. The level of ABA in cucumber (Cucumis sativus) plants under low-N conditions was significantly higher at 10 and 20 d after transplantation compared with that under sufficient-N conditions. Chlorophyll was preserved in the aerial parts of cucumber plants grown under low-N conditions in the presence of ABA, while there was no significant difference between control plants and ABA-applied plants under sufficient-N conditions. ABA suppressed the reduction of chlorophyll biosynthesis under low-N conditions but not under sufficient-N conditions. On the other hand, ABA decreased the expression of the chlorophyll degradation gene in older cucumber plants grown under both conditions. In addition, transcript and protein levels of a gene encoding a chlorophyll a/b binding protein were positively correlated with ABA concentration under low-N conditions. The chloroplasts in control plants were round, and the stack of thylakoid membranes was reduced compared with that of plants treated with ABA 10(-5) M. These results strongly suggest that ABA is accumulated in cucumber plants grown under low-N conditions and that accumulated ABA promotes chlorophyll biosynthesis and inhibits its degradation in those plants.
authors.affiliation: Tottori University, Koyamacho-minami 4-101, Tottori 680-8553, Japan. m.oka@muses.tottori-u.ac.jp
authors.forename: Mariko
authors.initials: M
authors.lastname: Oka
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Shimoda
authors.forename: Naoko
authors.initials: N
authors.lastname: Sato
authors.forename: Junya
authors.initials: J
authors.lastname: Inoue
authors.forename: Teru
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Norihiro
authors.initials: N
authors.lastname: Shimomura
authors.forename: Hideyasu
authors.initials: H
authors.lastname: Fujiyama
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry / Q000494:pharmacology*; D000375:Aging / Q000187:drug effects*; D002734:Chlorophyll / Q000096:biosynthesis; D000077194:Chlorophyll A; D061146:Chlorophyll Binding Proteins / Q000378:metabolism; D018553:Cucumis sativus / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000187:drug effects; D009584:Nitrogen / Q000172:deficiency*; D035261:Plant Components, Aerial / Q000737:chemistry; D010937:Plant Growth Regulators / Q000032:analysis
chemical_list: D061146:Chlorophyll Binding Proteins; D010937:Plant Growth Regulators; D002734:Chlorophyll; D000040:Abscisic Acid; D009584:Nitrogen; D000077194:Chlorophyll A