DISTRIBUTION OF COAGULATION OF YOUNG SHOOT HOMOGENATES IN THE AURANTIOIDEAE

Distribution of coagulation of young shoot homogenates was surveyed in 430 accessions from the orange subfamily Aurantioideae. Representatives of four genera available for study (Clausena, Glycosmis, Aegle, Feronia) were coagulating taxa. The genus Citrus included both coagulating and noncoagulating taxa. Nineteen genera (Murraya, Merillia, Pamburus, Paramignya, Triphasia, Aeglopsis, Afraegle, Balsamocitrus, Feroniella, Swinglea, Atalantia, Citropsis, Hesperethusa, Pleiospermium, Severinia, Clymenia, Eremocitrus, Poncirus, Fortunella) were noncoagulating. The status of eight genera (Micromelum, Wenzelia, Monanthocitrus, Oxanthera, Merope, Luvunga, Burkillanthus, Limnocitrus) is not known. Homogenized tissue from coagulating taxa turned into a paste while tissue from noncoagulating taxa was thin and juicy. Coagulation did not take place when the pH of the grinding medium was 11 or higher but it would occur if the pH was lowered. Homogenates of noncoagulating taxa become coagulated below pH 5.2–5.3, but remained noncoagulating above this. Noncoagulating taxa contained an unidentified substance which inhibited coagulation of tissue from coagulating taxa. The mechanism of coagulation and noncoagulaton is not presently known. The significance of coagulation and its absence as a taxonomic and genetic marker is discussed.