空气和土壤干旱对不同杨树种类无性系生长及光合的影响

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。

Effects of Air and Soil Drought on Photosynthesis and Growth of 4 Poplar Genotypes

Significant differences in tolerance to air and soil drought were found among 4poplar genotypes, Populus × euramericana cv;I-214(Italica),Populus × euramericana Guinircv,rthesta(Robusta),P,berolinensis(Berolinensis)and P;popularis’35-44(Popularis),in a potexperiment with l-year-old rcoted cuttings。Berolinensis was the most tolerant to air drought be-cause its stomata were insensitive to low air humidity,allowing for a keeping relatively high stom-atal conductance for gas exchange.However,it was the least tolerant to excessive soil water,I-talica and Rdssta were very responsive to soil droughtmand when soil moisture was lowered to40%FFC(full field capacity)a significant reduction of net photosynthetic rate(Pn),appeared。After suUected to severe soil drought(30%FFC)mabout one quarter of the leaves of droughtedplants of these two genotypes were shed and the growth of expanding leaves was dramaticallysuppressed,whereas only a moderate effect on growth was found,there was no leaf abscission atall for Berolinensis and Popularis. Although the severe soil drought significantly decreased Pn ofBerolinensts and Popularis as well in the first several days,an obvious recovery of Pn displayed in the 8th day of exposure to water shortage.Results showed that Berolinensis and Popularis weremore tolerant to soil drought than lsalica and Redusta。Consequently,tolerance of poplar geno-types to soil drought was ranked as follows,POpularis>Berolinensis>Robusta>Italica.