INFLUENCE OF PACLOBUTRAZOL AND MOISTURE STRESS CONDITIONING ON DROUGHT SUSCEPTIBILITY IN <em>ROBINIA</em> <em>PSEUDOACACIA</em> SEEDLINGS

Abstract

Robinia pseudoacacia nursery stock was conditioned with a combination
of paclobutrazol treatments and 2-3 moisture stress cycle, each of 5 days stress followed by 5 days rehydration. Both moisture stress and paclobutrazol (PP₃₃₃) conditioning improved water relations, enhanced drought tolerance and decreased the drought injury index of conditioned seedlings over unconditioned seedlings at subsequent water stress. Water stress
caused shoot and root dry weight reduction, although reduction was significantly less in paclobutrazol conditioned seedlings. Conditioning treatments maintained significantly higher leaf water potential in conditioned than unconditioned seedlings up to 16 days of water stress. Proline, total amino acid and soluble sugar contents were greater in PP₃₃₃ and moisture stress conditioned seedlings during subsequent water deficit. Drought injury index (Id) on the 16th day of water deficit was maximum (69.9%) in unconditioned seedlings, whereas Id for PP₃₃₃ and moisture stress conditioned seedlings varied between 23 and 36%.