Abstract:

The formation and development of fruit eyes were observed,the dynamic changes of tissues and organs related to fruit eyes were measured and analyzed by histological section and anatomy,using the crown,flower and fruit from different pineapple germplasm as the research materials. Three stages for the developmental of pineapple fruit eye,including antrum differentiation,antrum development and fruit eye development were divided,according to the formation processes.The flower cavity is the early morphology of fruit eye,and its differentiation and development lead to the formation of fruit eye,which takes about 70 days（d）,and the fruit setting is the sign for the beginning of fruit eye development stage. The morphological differentiation of flower cavity begins with calyx differentiation and ends with disk（receptacle and ovary）differentiation. 14 days after the flower induction,the calyx primordium differentiation is firstly observed in the bractus axils at the base of flower buds,from bottom to top. All the antrum differentiation in the inflorescence was finished until 35 days after the flower induction,while the antrum morphological differentiation of the florets at the top of inflorescence was about 7 d later than that at the base. The size,morphology and structure of the flower cavity are changed by the growth and development of flower organs during the flowering process. The peak period of the flower cavity enlargement is the first week after the completion of the morphological differentiation（36 to 42 d after flower induction）. At this time,significant differences for the depth of the flower cavity were found between the pineapple varieties with deep and shallow fruit eyes,and then the expansion slows down gradually. There was no significant difference in the absolute growth of flower disc among different cultivars,so the deepening of flower cavity mainly depended on the growth of calyx. The fruit eyes start to develop after the fruit setting. With the rapid expansion of fruit,the growth of the dorsal and ventral sides of calyx tube is unbalanced,and the persistent calyx curves inward. However,the bending speed and growth stop time are associated with the variety types. The mass growth of calyx for ‘MD-2’was few and internal bending was rapid,while for ‘Jintong’was large and slow. The eye deepened mainly within 14 days after fruit setting,and the shape and size of the eye no longer changed about 70 d after fruit setting. According to the depth of eye in the middle of ripe fruit,pineapple germplasm could be divided into three types：shallow eye depth < 0.9 cm,medium eye depth 0.9-1.2 cm,and deep eye depth > 1.2 cm. There was no significant difference in disc depth（about 0.29 cm）among different types of cultivars. The difference in fruit eye depth was mainly associated with the height of calyx,and the bending degree and growth of calyx were the main reasons for the difference in height of calyx and protrusion of small fruit. Therefore,the formation of fruit eyes begins with the differentiation of flower buds,in which calyx growth and development have a significant impact on the morphology and depth of fruit eyes. The morphological differences of fruit eyes among cultivars are mainly caused by the unbalanced growth of the dorsal and ventral sides of calyx tube within 14 d after the fruit setting,while the differences of fruit eye depth mainly occur in the first week of calyx development（36-42 d after flower induction）.

Key words: pineapple, floral cavity differentiation, pineapple’s eyes, calyx