Cork layer

Yam tubers of Dioscorea alata (Umudike cultivar), D. rotundata (asukwu and obiaturugo cultivars)" and D. cayenensis (water yam and Nkokpu cultivars) were obtained from the National Root Crops Research Institute, Umudike, Nigeria. Some tubers were stored 6 or 12 months at room temperature (25-27 °C), some in vacuum dessicators over a suitable dessicant, and some in paper bags placed in a dark cabinet (absence of circulating air). Fresh tubers were peeled by carefully scraping away the cork layer to minimize loss of outer tissue since much of the protein is concentrated here ( ). They were then cut into 2 cu. cm. pieces, quickly frozen with solid CO2 in 50 9 portions in plastic bags, and stored in a freezer until needed. 

The outer bark, which consists mainly of periderm or cork layers, protects the wood tissues against mechanical damage and preserves it from temperature and humidity variations. In most woody plants a periderm replaces the epidermis within the first year of growth. The first periderm in stems usually arises from the cork cambium in the outer surface of bark, either in the subepidermal layer or in the epidermis. The following periderms are then formed in successively deeper layers of the bark or in the bast tissue. Cork tissue is predominantly formed in the outward direction, but some division also occurs inward resulting in so-called phelloderm tissue resembling parenchyma cells. Owing to this sequence the final rhytidome usually occurs as scaly bark and, in addition to the cork cells, contains the same cells as those present in the bast. 

There very early originate in the region beneath the stomata loosely arranged cells from cork cambium which swell up during rain and rupture, forming convex fissures in the cork layer, called lenticels. 

HoUoway P.J., Some variations in the composition of suberin from the cork layers of higher-plants. Phytochemistry. 22(2), 1983, 495-502. 

Adamovics J A, Johnson G, Stermitz F R 1977 Ferulates from cork layers of Solanum tuberosum and Pseudotsuga menziesii. Phytochemistry 16 1989-1990... 

Holloway P J 1972 The suberin composition of the cork layers from some Ribes species. Chem Phys Lipids 9 171-179... 

June from trees at least 10 years old, rid of outer cork layer, cut into small sections, and sun dried. 

It has been suggested that the distribution of certain hypophloedal crus-tose lichens (those living under the outermost cork layers) is determined by... 

Adamovics JA, Johnson G, Stermitz FR. Ferulates from cork layers of Solatium tuberosum and Pseudotsuga menziesiu Phytochemistry 1977 16,1089-1090. 

Freise (164) emphasised that only stem and branch bark was used, and never root bark, but he did not specify the tribe(s) to which his remark applied. The cork layer of older bark was the preferred material for preparing the curare. 

Ethyl bromide soon distils over, and collects as heavy oily drops under the water in the receiving flask, evaporation of the very volatile distillate being thus prevented. If the mixture in the flask A froths badly, moderate the heating of the sand-bath. When no more oily drops of ethyl bromide come over, pour the contents of the receiving flask into a separating-funnel, and carefully run oflF the heavy lower layer of ethyl bromide. Discard the upper aqueous layer, and return the ethyl bromide to the funnel. Add an equal volume of 10% sodium carbonate solution, cork the funnel securely and shake cautiously. Owing to the presence of hydrobromic and sulphurous acids in the crude ethyl bromide, a brisk evolution of carbon dioxide occurs therefore release the... 

Now transfer the cold distillate to a separating-funnel, and shake vigorously with about 50-60 ml. of ether run oflF the lower aqueous layer and then decantf the ethereal solution through the mouth of the funnel into a 200 ml. conical flask. Replace the aqueous layer in the funnel, and extract similarly twice more with ether, combining the ethereal extracts in the conical flask. Add 3-4 g. of dry powdered potassium carbonate to the ethereal solution, securely cork the flask and shake the contents gently. The ethereal solution of the phenol... 

Place 5 ml. of benzaldehyde in a wide-necked stout-walled bottle of about 100 ml. capacity (a conical flask is too fragile for this purpose) and add 50 ml. of concentrated dy 0 880) ammonia solution. Cork the bottle securely, shake vigorously, and then allow to stand for 24 hours, by which time the layer of benzaldehyde at the bottom of the bottle will have been converted into a hard mass of hydrobenzamide. (If after 24 hours the crude hydrobenzamide is still syrupy, shake the mixture vigorously and allow to stand for another hour, when the conversion will be complete.) Break up the solid pellet with a strong spatula, filter at the pump, wash with water and drain thoroughly. Recrystallise from ethanol methylated spirit should not be used, as it contains sufficient water to cause partial hydrolysis back to benzaldehyde and ammonia. Hydrobenzamide is obtained as colourless crystals, m.p. 101° (and not 110° as frequently quoted) yield, 4 g. 

Place 50 g. of anhydrous calcium chloride and 260 g. (323 ml.) of rectified spirit (95 per cent, ethyl alcohol) in a 1-litre narrow neck bottle, and cool the mixture to 8° or below by immersion in ice water. Introduce slowly 125 g. (155 ml.) of freshly distilled acetaldehyde, b.p. 20-22° (Section 111,65) down the sides of the bottle so that it forms a layer on the alcoholic solution. Close the bottle with a tightly fitting cork and shake vigorously for 3-4 minutes a considerable rise in temperature occurs so that the stopper must be held well down to prevent the volatilisation of the acetaldehyde. Allow the stoppered bottle to stand for 24-30 hours with intermittent shaking. (After 1-2 hours the mixture separates into two layers.) Separate the upper layer ca. 320 g.) and wash it three times with 80 ml. portions of water. Dry for several hours over 6 g. of anhydrous potassium carbonate and fractionate with an efficient column (compare Section 11,17). Collect the fraction, b.p. 101-104°, as pure acetal. The yield is 200 g. 

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