H. A. Collin

Presence of alliinase in isolated vacuoles and of alkyl cysteine sulphoxides in the cytoplasm of bulbs of onion (Allium cepa)

Abstract Protoplasts were isolated from the inner scales of mature onion bulbs, then the vacuoles liberated from the protoplasts by gentle osmotic shock. Protoplasts and vacuoles were compared for alliinase activity (alliin alkylsulphenate-lyase, EC 4.4.1.4). The vacuoles contained alliinase in amounts which account for the alliinase found in protoplasts. Both vacuoles and protoplasts were analysed for S -alkyl substituted cysteine sulphoxides by electrophoresis-thin-layer chromatography (TLC). Whereas the vacuoles contained negligible amounts of alkyl cysteine sulphoxides, the cytoplasm of the protoplasts contained a considerable amount of alkyl cysteine sulphoxides. It is concluded that alliinase and alkyl cysteine sulphoxides are prevented from acting in the intact protoplast by compartmentation of the alliinase in the vacuoles and alkyl cysteine sulphoxides in the cytoplasm.

Flavour compounds in tissue cultures of celery

Abstract The main flavour compounds of celery are the phthallides and these were extracted from undifferentiated and differentiated callus and intact celery plants. Two phthallides, 3-isobutylidene-3a,4,5,6-tetrahydrophthallide and 3-isobutylidene-3a,4-dihydrophthallide were identified by gas chromatography-mass spectrography (GC-MS) in the intact plant and the differentiated callus but appeared to be absent in the undifferentiated callus. In suspension culture the differentiated tissue produced a large number of embryos, most of which were at the torpedo stage after three weeks. The phthallide composition of this culture was comparable to that of the intact plants.

Biochemical and physiological aspects of leaf development in cocoa (Theobroma cacao). IV. Changes in growth inhibitors

Abstract Cocoa seedlings were grown under greenhouse conditions in the absence of any environmental stress. During a flush cycle of shoot growth, leaves of the current flush and of the previous flush were sampled at intervals and ABA levels determined by bioassay. In young expanding flush leaves (stages F-1 to F-2) amounts of both free and bound abscisic acid (ABA) were low. At full expansion (end of F-2 stage) both forms increased, particularly the bound ABA, then declined again during the dormant period (I-1 to I-2) to reach a low level at the start of the new cycle. In the leaves of the previous flush, the early stage of the cycle (F-2) was marked by a high level of free ABA which thereafter declined rapidly and remained low throughout the rest of the cycle, whereas the bound form increased at the end of F-2 and only declined at the end of the cycle. It is suggested that both the mature leaves of the current flush and the leaves of the previous flush act as sources of ABA which maintain the bud in a state of dormancy during the latter half of the growth cycle.

Selection for Asulam resistance in tissue cultures of celery

Abstract Cell suspension cultures of celery were incubated with Asulam concentrations of 8 × 10 −5 M for one week, then the single cells and small cell aggregates were plated in Asulam free medium. The survivors were re-selected at the same concentration, then the final surviving colonies subcultured in Asulam free medium for 15 subcultures. A comparison of the growth of the selected and unselected clones in the presence of Asulam showed the selected clone to be unaffected by Asulam. It is suggested that the selected clone was an Asulam resistant mutant.