叶斑病对白桦树干液流的影响

应用热扩散法，对白桦树干液流进行连续两个生长旺期测定。与健康白桦相比，患叶斑病的白桦树干液流格局发生明显改变。在晴天树干液流密度日变化由单峰曲线转变为双峰曲线，或单峰曲线峰值较光合有效辐射峰值显著提前或推后；液流密度峰值及全天均值远远低于同期的健康白桦，且晚上及凌晨输水比例明显升高，表明晚上主要靠根压输送水分，维持光合作用必需原料及生长所需的矿物质；并且此时树干液流密度变化受外界环境因子的决定比重减小或根本无相关显著的环境因子。叶感病白桦树干液流具有以上特点，是因为具有较强的蒸腾生理调控力，以适应叶部病害而求得生存。

Effect of leaf spot on the stem sap flow of Betula platyphylla

Thermal dissipation method was applied to study the stem sap flow of Betula platyphylla for two consecutive growing seasons. Compared to the healthy Betula platyphylla in the year 2000, diurnal stem sap flow pattern changed significantly after effecting the leaf spot in 2001 during its sunny diurnal process. Diurnal sap flow was two-peak or mono-peak patterns which maximum sap flow density of the day was not corresponding to photosynthetically active radiation, whereas mono-peak pattern in the year 2000. Diurnal maximum and mean sap flow density of the ailing Betula platyphylla were significantly less than the healthy one in 2000, whereas sap flow ratio of evening and morning to total sap flow of the whole day in 2001 was higher than 2000, showed that root pressure got into effect. Results of the regression analysis between diurnal sap flow density and environmental factors showed that adjust R~2 in 2001 was less than the value of 2000, even there was no significant correlative environmental factors. Stem sap flow density characteristics of ailing Betula platyphylla in 2001 was concerned with physiological control of transpiration.