Biological characteristics and fruit drop of Carya illinoensis ‘Mahan'
The flowering and fruiting habits of ‘Mahan' pecan were observed to study its biological characteristics and physiological fruit drop. The results showed that the pecan buds on the fruiting spur are usually mixed buds in near-round shape and tightly packed with scales. After germination, fruit bearing-branches elongated and compound leaves appeared. The male inflorescence was developed from the lateral buds on the low portion of the branch and the female inflorescence was developed from the proximal top of the branch. From mid to late March, buds swelled and their outer scales shed. The inner scales split and the male inflorescence appeared and bloomed on an extended fruiting branch from the apical bud in late March. In early April, leaves expanded and reached the maximum size after 20-d growth. The growth patterns of the fruit-bearing branch, compound leaf, leaf length and leaf width all showed an "S" curve, which highly fit in the logistic growth model. A correlation analysis indicated a significantly positively correlation between the growth and the effective accumulated temperature. The first time of the fruit dropping occurred at early to late June with a fruit dropping rate of 16.27%. The second time of the fruit dropping occurred from early to mid July with a fruit dropping rate of 68.75%. The third fruit dropping time was in August with a fruit dropping rate of 2.2%.