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对杨树无性系Ｉ－２１４（Ｐｏｐｕｌｕｓｅｕｒａｍｅｒｉｃａｎａｃｖ，‘Ｉ－２１４’）、健杨（Ｐｏｐｕｌｕｓ×ｅｕｒａｍｅｒｉｃａｎａＧｕｉｎｉｒｃｖ．ｒｏｂｕｓｔａ）、中东杨（Ｐ．ｂｅｒｏｌｉｎｅｎｓｉｓ）和群众杨（Ｐ．‘ｐｏｐｕｌａｒｉｓ３５－４４’）１年生插条苗进行盆栽试验，发现它们对空气和土壤干旱的耐性存在很大差异，其中Ｂｅｒｏｌｉｎｅｎｓｉｓ对空气干旱的耐性最强，对土壤水湿的耐性最弱；Ｉｔａｌｉｃａ和Ｒｏｂｕｓｔａ对土壤干旱反应敏感，当田间持水量（ＦＦＣ）降至４０％时，净光合速率（Ｐｎ）已显著降低，严重干旱（３０％ＦＦＣ）时，苗木下部１／４叶片脱落，同时，上部叶面积生长受到很大抑制；Ｂｅｒｏｌｉｎｅｎｓｉｓ和Ｐｏｐｕｌａｒｉｓ虽在干旱初期Ｐｎ下降显著，但７ｄ后Ｐｎ不同程度回升，并且受旱期间叶面积生长受到的影响较小，即显示出对土壤干旱的耐性，因此，杨树无性系对土壤干旱耐性依次为Ｐｏｐｕｌａｒｉｓ＞Ｂｅｒｏｉｉｎｅｎｓｉｓ＞Ｒｏｂｕｓｔａ＞Ｉｔａｌｉｃａ。
Populations of poplar clones I-214 (Populuseuramericanacv, ’I-214’), Populus × euramericanaGuinircv .robusta, P.berolinensis and P. popularis35-44 ’ Potted seedlings were potted and found that there was a great difference in their resistance to air and soil drought. Among them, Berolinensis had the strongest resistance to air drought and the weaker water resistance to soil moisture. Italica and Robusta were sensitive to soil drought. The net photosynthetic rate (Pn) decreased significantly when the FFC decreased to 40%. In the case of severe drought (30% FFC), the lower 1/4 leaf of the seedling fell off and the growth of the upper leaf area was greatly inhibited. Although Popularis decreased significantly during the early drought period But 7d Pn rebounded to varying degrees, and leaf area growth was less affected by drought during that show tolerance to soil drought, therefore, poplar clones to soil drought tolerance were Popularis> Beroiinensis> Robusta> Italica.