| Three low-maintenance ground cover rose cultivars (Rosa hybrida cv. Meiflopan, Meiplatin and Meineble.) were subjected to five consecutive water stress cycles. Water stress decreased leaf number, leaf area, shoot growth rate, shoot and root dry weight, leaf area ratio, relative growth rate, and net assimilation rate while root:shoot ratio and epicuticular wax content were increased. Decreased shoot growth rate, leaf number, and leaf area were useful parameters for evaluating water stress response, while epicuticular wax content may be one of the important drought resistant mechanisms. Drought resistant in Meiflopan occurred with greater leaf abscission, smaller leaf size and leaf area, and higher epicuticular wax content. Drought resistant in Meineble occurred with a larger shoot dry weight, reduced leaf abscission, smaller shoot growth rate, and higher relative growth rate relation to other cultivars during drought. Drought resistant characteristics of Meiplatin were intermediate with the other two cultivars.; Water stress decreased gas exchange rate, stomatal conductance, and whole plant transpiration rate. The cultivar Meineble had higher leaf elemental contents of N, Mg, Fe, Cu, Zn, Mo, and Na, while Meiplatin was higher in Ca and Al, regardless of water stress conditions.; Mycorrhizal and non-mycorrhizal plants had equal evaporative surface and similar P concentration levels. Mycorrhizal inoculation had no significant effect on predawn leaf water potential ({dollar}Psisb{lcub}leaf{rcub}{dollar}), whole plant transpiration rate, and relative water content. Mycorrhizal plants had greater water demand under water stress conditions as shown by a more rapid decrease in {dollar}Psisb{lcub}leaf{rcub}{dollar}. Drought stress enhanced mycorrhizal colonization. Mycorrhizal plants had increased root dry weight, relative growth rate, and net assimilation rate. Mycorrhizal roots had greater growth than non-mycorrhizal roots. Under drought stress conditions, there was a tendency for mycorrhizal plants to osmotically adjust by having a lower osmotic potential ({dollar}Psisbpi{dollar}), and higher pressure potential ({dollar}Psisb{lcub}p{rcub}{dollar}) than non-inoculated plants. Water stress decreased sucrose, total sugars, and quinic acid contents in leaf tissue. Mycorrhizal enhancement of plant water relations was not attributable to higher leaf P concentration. |
