Tree hydrangeas drought resistance parameters in the Southern Urals (Ufa)

The purpose of the study is a comparative assessment of the resistance of tree-like hydrangeas to drought and the identification of the most promising taxa suitable for growing in the conditions of the sharply continental climate of the Bashkir Cis-Urals. The resistance of moisture-loving tree-like hydrangeas to drought was studied in the collection of the South Ural Botanical Garden-Institute of the Ufa Federal Research Center of the Russian Academy of Sciences. Tree hydrangeas in the collection are represented by 2 species, 1 subspecies and 7 varieties. Their water regime was studied, which includes such indicators as water-retaining capacity, total water content and the content of mobile moisture in the leaves during the period of budding and flowering. It was established that the total water content of all studied taxa of tree-like hydrangeas during the budding period varied in the range from 69.4 to 74.6 %, the water-holding capacity during this period ranged from 5.1 to 18.3 %. A low level of mobile moisture was noted in H. arborescens (54.1 %) and H. arborescens White Dome (58.5 %), which means a higher drought resistance of these taxa. A high content of mobile moisture was recorded in H. arborescens Strong Annabelle and H. arborescens Pink Annabelle - 67.0 and 68.9 %, indicating a reduced drought resistance of these varieties. During flowering, all taxa showed a decrease in total water content. The lowest indicator of moisture mobility during flowering is observed in H. arborescens - 54.1 % and H. arborescens ‘White Dome’ - 58.5 %, indicating a higher drought resistance of these taxa. Thus, all studied taxa endure short periods of drought without morphological damage, without losing their decorative qualities. Among the varieties, H. arborescens Bounty, H. arborescens White Dome, H. cinerea Grandiflora turned out to be the most drought-resistant.