Phospholipids and the Phospholipid Fatty Acids of Germinating Hazel Seeds (Corylus avellanaL.)

Abstract

An analysis of the phospholipids and phospholipid fatty acids of germinating hazel seeds has been carried out. The phospholipid content of the cotyledons and embryonic axes increased during germination. Early increases in the relative amounts of phosphatidyl glycerol and decreases in the relative amounts of phosphatidyl ethanolamine occurred in both cotyledons and axes. The later stages of germination were accompanied by further changes in the phospholipid composition of the axes. Increases in the degree of unsaturation of the C18 fatty acids occurred in both tissues. INTRODUCTION Phospholipids are major components of all cell and intracellular membranes. The importance of the phospholipid composition in determining the permeability properties of natural and artificial membranes (van Deenen, 1969 ; Haest, de Gier, op den Kamp, Bartels, and van Deenen, 1972; de Gier, Mandersloot, and van Deenen, 1968) and the activity of active transport systems (Israel, 1969 ; Meissner and Fleischer, 1972) and membrane-bound enzymes (Katchalski, Silman, and Goldman, 1971 ; Rothfeld and Finkelstein, 1968) is well established. It is possible that changes in the phospholipid composition of membranes are important in regulating plant development. Quarles and Dawson (1969) have studied the phospholipid composition of germinating cotyledons of pea and Zimmerman and Klosterman (1965) report analyses of the phospholipid acyl fatty acid composition of germinating flax seed. The present report describes changes in the phospholipid and phospho lipid fatty acid composition of cotyledon and embryonic axes of germinating hazel seeds. MATERIALS AND METHODS Fruits of Corylus avellana (L.) (Kent Cob Nuts) were purchased from R. Gould, Mereworth, Kent. After deshelling and sterilizing, the seeds were imbibed for 24 h in H20 and placed in the dark in Petri-dishes containing 20 ml of 3 x 10~4 M GA3. The hormone treatment results in breaking of the dormancy of the seed (Frankland and Wareing, 1966). At intervals samples 1 Present address : Department of Botany, Westfield College, London, NW3 7ST. 2 To whom all communications for reprints should be sent. This content downloaded from 157.55.39.114 on Mon, 25 Apr 2016 05:15:30 UTC All use subject to http://about.jstor.org/terms Phospholipids in Germinating Corylus Seeds 1101 of cotyledon and embryonic axis tissue were harvested and the lipids extracted and fractiona ted into polar and neutral lipid (Stobart and Pinfield, 1970). Embryonic axes from seedlings up to 12 d old were extracted whole. Fifteen-day-old axes were subdivided into plumules, radicles-)-hypocotyls, and cotyledonary petioles, each part being extracted separately. The phospholipid content of the polar lipid fractions was determined as inorganic phosphate by a modification of the Bartlett procedure (Marinetti, 1964). The absence of glycolipids in the polar lipid fractions permitted the phospholipids to be separated by one-dimensional thin-layer chromatography using Kieselgel G plates (0-25 mm) and CHCl3/Me0H/H0AC/H20 (85:15:10:3-5, v/v). After development the plates were sprayed with 50 per cent H2S04 and charred for 20 min at 220 °C. Quantitative measurements