SOME EARLY RESPONSES OF HELIANTHUS-ANNUUS L TO FLOODING .1. THE EFFECTS OF FLOODING ON THE UPTAKE AND LEAKAGE OF NON-ELECTROLYTES BY ROOTS

The object of this work was to examine some of the early effects of flooding on roots. A hydroponic system was developed that gave good control over watering, degree of oxygenation of the bathing medium and allowed measurement of short term changes in the composition of the bathing medium. Excised roots, flooded for 24 h, were shown to take up less [3H].beta.-alanine than non-flooded roots and also leaked more [3H].beta.-alanine into a distilled water bathing medium. Further, flooded excised roots lost more protein to the bathing medium, with ''young'' (5-7 d) roots showing greater losses than ''old'' (11-14 d) roots. However, young roots had more protein in the tissue even after greater loss. Young roots remained healthier and lost less fresh weight than old roots. Abscisic acid was shown to have a small role in protecting ''young'' roots from the effects of flooding.