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Nitrate reductase in cotyledons of cucumber seedlings as affected by nitrate, phytochrome and calcium
Author(s) -
Bergareche Carmen,
Ayuso Roberto,
Masgrau Carles,
Simon Esther
Publication year - 1994
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1994.tb00427.x
Subject(s) - etiolation , phytochrome , nitrate reductase , darkness , cucumis , calcium , calcium nitrate , nitrate , botany , horticulture , chemistry , biology , biochemistry , enzyme , red light , organic chemistry
Regulation by the active form of phytochrome (P FR ) and the effect of Ca 2+ was examined with nitrate reductase (NR) in etiolated cucumber ( Cucumis sativus cv. Beilpuig). Nitrate reductase activity (NRA) was studied in excised cotyledons of cucumber seedlings grown in distilled water and in darkness for seven days at 24 ± 0.5°C. All experiments were performed in the dark and a dim green safelight was used during analyses. In etiolated cucumber cotyledons NRA was induced by nitrate and a brief irradiation (15 min) with red light (R) resulted in 62% increase in NRA. This effect was nullified when R was followed immediately by a brief (5 min) far‐red light (FR). NRA also showed a semidian (12 h) rhythmicity. Both P FR , and nitrate effects were age dependent. Calcium seemed to be involved since the phytochrome effect was only observed when calcium was supplied in the external solution. The effect of R on NRA depended on the period of calcium nitrate incubation. An external supply of calcium ionophore mimicked the effect of R and, if supplied to R‐irradiated cotyledons, produced a higher NR level than that caused by R alone. This suggested that intracellular free calcium was involved.