The expected response of acacia karroo hayne to moisture stress and defoliation

Abstract

The generalised growth of woody species and their response to defoliation is presented to provide a conceptual background for an examination of the growth of Acacia karroo and its response to defoliation. Particular attention is paid to water stress and the role it plays in determining the conditions of existence for woody plants. The nutritional and hormonal control of growth in woody plants is considered. Carbohydrate reserves are important in regrowth, but even where carbohydrate supplies appear to be adequate, growth is inhibited. In such cases a deficiency of plant hormones may account for this inhibition. Water stress that inhibits growth does not necessarily reduce carbohydrate reserves. The ontogeny and annual growth cycles of A. karroo are given and possible reactions to water stress and defoliation are outlined.

Uittreksel

Die veralgemeende groei van houtagtige soorte en hulle reaksie op ontblaring word gegee am ‘n begrips‐ agtergrond te skep vir ‘n ondersoek van die groei van Acacia karroo en sy reaksie op ontblarings. Besondere klem word gelê op vogspanning en die rol wat dit speel by die bepaling van bestaanstoestande van houtagtige plante. Die voedings en hormoonbeheer van groei in houtagtige plante word b'eskou. Koolhidraat reserwes is belangrik by hergroei maar selfs waar koolhidraat voorraade skynbaar voldoende is word groei soms inhibeer. In sulke gevalle mag ‘n tekori aan planthormone of versteuring van voedingstofbalans die oorsaak van die inhibisie wees. Vogspanning, wat groei inhibeer, verminder nie noodwendig die koolhidraatreserwes nie. Die ontogenie en jaarlikse groeisiklusse van A. karroo word gegee en moontlike reaksie op vogspanning en ontblaring word uitgestip.