柑橘叶脉开裂症与矿质营养的关系

 柑橘叶脉开裂症属于多病因的病症，缺Mg或缺B均可导致发病。对‘纽荷尔’脐橙Citrus sinensis（L.）Osbeck‘Newhall’]的缺Mg叶脉开裂症病株，在生长季4月采用1.0%硝酸镁叶面喷施矫治2 ~ 3次，可有效降低病叶发生。通过福建柑橘产区普查，由缺Mg引起叶脉开裂症占86.2%，其次为B与Mg共同缺乏，缺B仅占2.3%。不同品种缺Mg叶脉开裂的感病顺序为：纽荷尔脐橙＞琯溪蜜柚，其它发病品种还有金柑、早熟温州蜜柑、瓯柑。采用易感品种纽荷尔脐橙与抗性品种椪柑互为中间砧高接比对发现，纽荷尔脐橙对Mg和B的吸收能力低于椪柑，对K的吸收高于椪柑，这可能是纽荷尔脐橙易患叶脉开裂症的原因。缺Mg和缺B病症的最显著的区别为，缺Mg叶脉开裂多位于叶片顶部“∧”形黄化部位；缺B叶脉开裂症病叶呈绿色不黄化；Mg、B缺乏症的病叶主脉和侧脉明显开裂与全叶黄化，或叶脉开裂达基部“∧”形绿色区域。

Relationship Between Leaf Vein Splitting and Mineral Nutrition of Citrus

This study confirmed that leaf vein splitting of citrus was multi-pathogeny caused by both Mg-deficiency and B-deficiency. Spraying 1.0% Mg(NO₃)₂ &;#8226; 6H₂O had significant effect on remedying leaf vein splitting of‘Newhall’Citrus sinensis（L.）Osbeck] caused by Mg-deficiency in April. According to the investigation in Fujian citrus orchards，86.2% of leaf vein splitting was suffered from Mg-deficiency，11.5% from Mg-deficiency and B-deficiency，only 2.3% from B-deficiency. Infection rates of leaf vein splitting caused by Mg-deficiency ranked in descending order was as follow：Newhall navel orange，‘Guanxi-miyou’C. grandis（L.）Osbeck]. Other infected varieties included‘Kumquat’（Fortunella crassifolia Swingle），Satsuma mandarin（C. unshiu Marc.‘Early variety’）and‘Ougan’（C. suavissima Hort. ex Tanaka）. Leaf vein splitting susceptible variety Newhall C. sinensis（L.）Osbeck] and resistant varieties Ponkan（C. reticulate Blanco）were used as intermediate stocks in graft of Ponkan or Newhall. Comparing with Ponkan，Newhall absorbed less Magnesium and Born，but more potassium，which may explain Newhall sensitive to leaf vein splitting. There was significant difference symptom between Mg-deficiency and B-deficiency. Infected leaf caused by Mg-deficiency had ∧-shaped etiolate in leaf top and vein splitting normally appeared in this part. Leaf caused by B-deficiency kept green. Infected leaf caused by Mg-deficiency and B-deficiency had symptom of full leaf etiolate，main and lateral veins splitting obviously or veins splitting to the leaf base with ∧-shaped green.