WATER RELATIONS, HORMONAL LEVEL, AND SPECTRAL REFLECTANCE OF GERBERA-JAMESONII BOLUS SUBJECTED TO CHILLING STRESS

One-gear-old gerbera plants subjected to 1 night at 5C had reduced lea f water losses and chlorophyll content and increased root hydraulic re sistance, but stomatal conductance and leaf water potential did not ch ange. After 3 nights,leaf water potential had decreased and leaf refle ctance in the visible and the near-infrared had increased. Similarly, abscisic acid (ABA) in leaves had increased and cytokinins (CK) in lea ves and roots had decreased, but ABA levels in roots did not change. A fter 4 days at 20C, root hydraulic resistance, reflectance and leaf wa ter loss returned to their initial values, but leaf water potential an d chlorophyll content remained lower. Leaf ABA levels reached values l ower than the initial, while root ABA and leaf CK levels retained the initial values. These data suggest that in the gerbera plants studied, 3 nights at 5C produced a reversible strain but otherwise plants rema ined uninjured, so this gerbera variety could be cultured with low ene rgetic inputs under Mediterranean conditions. The results mag indicate that ABA and CK were acting as synergistic signals of the chilling st ress. Spectral reflectance signals seemed to be useful as plant chilli ng injury indicators at ground level.