Wax metabolism in the leaves of Brussels sprout

Abstract

IN connection with an investigation which is being made in this laboratory into the metabolism of paraffins in the higher plants it was thought that further light might be thrown on the chemistry of paraffin synthesis in the leaf if the composition of a leaf-wax known to contain large amounts of paraffin could be determined at various stages throughout the life history of the leaf. The wax of cabbage leaves (Brassica oleracea v. capitata), which was shown by Channon and Chibnall [1929] to consist chiefly of the paraffin n-nonacosane and the closely allied ketone 15-nonacosanone would have been a suitable one for such an experiment, but unfortunately the headed cabbage, which is a bud with its leaves densely compacted together and in different degrees of maturity, is unsuitable for this purpose. The Brussels sprout (B. oleracea v. gemmifera) on the contrary appeared to be quite suitable for this purpose and as the botanical difference between the two plants is a varietal one only it seemed to us probable that the leaf-waxes would be similar. Accordingly we first determined the composition of the Brussels sprout leaf-wax and having found that it consisted chiefly of n-nonacosane, 15-nonacosanone and 15-nonacosanol we investigated the change in composition throughout the life history of the leaf.In the experiments detailed below it is to be clearly understood that the term Brussels sprout leaf refers to the leaves growing on the main axis of the plant, and is in no way concerned with the bud-like shoots commonly referred to as "sprouts."Analysis of the wax. Several samples of wax ("crude hydrocarbon") had been obtained in a previous research from the mature leaves of Brussels sprout by Chibnall and Sahai [1931]. These were collected and saponified and the unsaponifiable material (22 g.) was fractionated by the phthalate method of Chibnall et al. [1931].Primary alcohols. Only a small amount of insoluble sodium salts of primary phthalates was obtained. This was thoroughly extracted with ether and then 1 The melting-points recorded in this paper were obtained by the method described by Piper et al. [1931] and are corrected.

The Relation of the Characteristics and Yield of Wax to Plant Age

“…However, in the most mature leaves the degree of unsatura- tiona rapidly decreased in S. halepense and increased rapidly in P. dactylifera. The increase with age of unsaturation of the fatty constituents is in agreement with previous work (8,13), but the significance of the rapid decrease of the iodine number with age of S. halepense is not known. It may be that as the old plant parts become desiccated, the unsaturated lipid compounds of this species are oxidized more rapidly by atmospheric oxygen.…”

“…According to earlier studies on Brussels sprout (13) and the runner bean (8), wax is steadily synthesized as the plant matures and is not catabolized. If this behavior is considered general, then the decrease with age of wax yield in several cases of the present study was only an apparent decrease.…”

Cutin, Suberin, and Waxes

“…Wax components applied to leaf surfaces undergo metabolic interconversions (Kolattukudy and Liu, 1970;Cassagne and Lessire, 1975). From measurements of the amount of wax present on brussels sprout and bean plants during their growth period, Chibnall and co-workers concluded that weathering was probably the only significant reason for loss of cuticular waxes (Sahai and Chibnall, 1932;Jordan and Chibnall, 1933;Chibnall and Piper, 1934), and to date little evidence to the contrary is avail able. From measurements of the amount of wax present on brussels sprout and bean plants during their growth period, Chibnall and co-workers concluded that weathering was probably the only significant reason for loss of cuticular waxes (Sahai and Chibnall, 1932;Jordan and Chibnall, 1933;Chibnall and Piper, 1934), and to date little evidence to the contrary is avail able.…”

Effect of Moisture Stress and Leaf Age on Bentazon Absorption in Common Cocklebur (Xanthium strumarium) and Velvetleaf (Abutilon theophrasti)

“…Epicuticular wax (ECW) 4 formation is a continual process on all plant organs except roots (8,17). Air temperature, moisture stress, radiant energy, relative humidity, air pollutants, plant age, and certain soil-applied pesticides are factors that affect the quantity and quality of ECW deposition (2,5,10,19,20,23).…”