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The dynamics of the flavour precursors, the S‐alk(en)yl‐L‐cysteine sulphoxides, during leaf blade and scale development in the onion ( Allium cepa )
Author(s) -
Lancaster Jane E.,
McCallion Barbara J.,
Shaw Martin L.
Publication year - 1986
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.1399-3054.1986.tb02423.x
Subject(s) - flavour , cysteine , allium , ripening , liliaceae , sulfoxide , chemistry , botany , horticulture , biology , food science , biochemistry , organic chemistry , enzyme
This study was undertaken to determine the patterns of accumulation and loss of the flavour precursors. (+) S‐1‐propyl‐L‐cysteine sulphoxide, (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide, and (+) S‐1‐methyl‐L‐cysteine sulphoxide, during the development and senescence of the leaf blades and scales of a brown onion ( Allium cepa L. cv. Pukekohe Longkeeper). The levels of the flavour precursors were related to the ontogeny of the individual leaf blade and scale, and the ontogeny of the entire plant. Leaf blades which developed on a young or bulbing onion contained all 3 flavour precursors (total of about 50–70 mg leaf −1 ); but as each attached scale developed, the leaf blades lost their flavour precursors. All 3 flavour precursors increased in the developing scales and decreased in the senescing scales. Leaf blades which developed on an older, ripening onion contained, and then lost, only (+) S‐1‐propyl‐L‐cysteine sulphoxide, whilst the scales accumulated only (+) S‐1‐propyl‐L‐cysteine sulphoxide; (+) S‐1‐methyl‐L‐cysteine sulphoxide and (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide were minimal. In the main scales of the onion, which did not senesce during ripening, there was a transition between these two patterns. These scales accumulated all 3 flavour precursors with (+) S‐1‐propyl‐L‐cysteine sulphoxide remaining constant at about 30 mg/scale; however there was a 10 fold loss of the other 2 flavour precursors (from 20 to about 2 mg/scale). The base plate (true stem) contained mainly (+) S‐1‐propyl‐L‐cysteine sulphoxide, which increased 5 fold in amount during bulbing. The other 2 flavour precursors were present at much lower levels. A recycling of flavour precursors is suggested, with the leaf blades supplying flavour precursors to scales, and in turn older senescing scales recycling their flavour precursors to developing younger scales.