核桃叶片早衰与叶片矿质元素含量的关系

Relationship of Presenility Pathogenesis and Mineral Elements Contents of Walnut Leaves

核桃（Juglans regia）是重要的经济树种之一。我国是世界上核桃产量最多的国家，但由于栽培的大部分是实生繁殖的普通核桃，后代分离变异甚大，从产量到品质，株间均表现出很大差异（段红喜等，2004）。因而造成商品质量混杂，无力参与国际竞争。为了提高我国的核桃品质，近年来我国广泛推行了早实核桃良种化栽培。在早实核桃栽培过程中，出现了叶片早衰现象，影响核桃的产量和质量。有些学者（郑进光，1995；杨家彦，2001；栾峰，2002）认为叶片早衰可采用外观诊断法作为叶片生理性病害进行诊断；核桃叶片早衰的外观症状与缺锰造成的最新成熟叶片脉间失绿（李玉敏，2005）相似。但是，对核桃叶片早衰的发生机理，未见前人报道。为此，我们于2003-2004年，在河北省临城县绿岭果业公司核桃生产基地，对核桃叶片早衰与叶片矿质元素含量的关系进行了初步探讨。

In order to study the presenility pathogenesis of walnut leaves, changes of main mineral elements contents in presenility leaves at different stages and healthy leaves at the. same stages were measured. The results showed that N contents in healthy leaves at different stages were 23.4,21.4,22.9,19.8 g·kg^-1 respectively, but in presenility leaves were 22.3,18.2, 18.6,17.6 g·kg^-1 respectively. N contents in healthy leaves were higher than that of presenility leaves except at the initial stage of the disease. P contents in healthy leaves at different stages were 1.3,1.5,1.5,1.4 g·kg^-1 respectively, but in presenility leaves were 1.1,1.4,0.6,0.6 g·kg^-1 respectively, P contents in healthy leaves were significant higher than that of presenility leaves, in the later stage of the disease P content in healthy leaves was very significant higher than that of presenility leaves. Mn contents in healthy leaves were very significant higher than that of presenility leaves after middle stage of the disease. Ca contents in healthy leaves at different stages were 34.7,30.9,34.1,35.5 g·kg^-1 respectively, but in presenility leaves were 33.3,34.3, 37.9,43.3 g·kg^-1 respectively, Ca content in presenility leaves was very significantly higher than that of healthy leaves in the later stage of the disease. Fe contents in healthy leaves were very significant higher than that of presenility leaves in the middle and later stage of the diseases. There exited significant negative correlations between Mn contents and disease process, the correlation coefficient was - 0. 975 0. There exited significant positive correlation between Ca contents and disease process, the correlation coefficient was 0.952 6. There exited very significant negative correlations between the ratios of MrdCa and MrdFe, the correlation coefficients were - 0.993 4 and - 0.991 4. The path coefficients showed that the direct path coefficient of Ca was - 3.921 ,and it was the largest; next was Mn, that was -2.959; total N was the lowest, only -0.249.