Phalaenopsis

Phalaenopsis (), also known as moth orchids, is a genus of about seventy species of plants in the family Orchidaceae. Orchids in this genus are monopodial epiphytes or lithophytes with long, coarse roots, short, leafy stems and long-lasting, flat flowers arranged in a flowering stem that often branches near the end. Orchids in this genus are native to Asia, New Guinea, and Australia, but mostly occur in Indonesia and the Philippines.

Description

Orchids in the genus Phalaenopsis are monopodial epiphytic, sometimes lithophytic herbs with long, coarse roots with pneumatodes (which allow for gaseous exchange of the photosynthetic roots), and short leafy stems hidden by overlapping leaf bases. The leaves are usually arranged in two rows, relatively large and leathery, oblong to elliptic and sometimes succulent. A few to many, small to large, long-lasting, flat, often fragrant flowers are arranged on erect to hanging racemes or panicles. The sepals and petals are free from and spread widely apart from each other. The lateral sepals are usually larger than the dorsal sepal and the petals much wider than the sepals. The labellum is joined stiffly to the column and has three lobes. The side lobes are erect and more or less parallel to each other and the middle lobe sometimes has a pair of appendages or antennae.

Reproduction

Unlike most other angiosperms, the development of the ovules is triggered by pollination. Therefore a temporal mismatch of male and female gametes exists (i.e. the male structures are ready but the female structures have not yet been fully developed). In orchids, fertilisation occurs within days or months after the pollination event. After pollination occurs, the stigmatic cavity is often closed through swelling of the column. As a result, the pollinia are completely enclosed. The pollen germinates after enclosure and tubes are produced. In Phalaenopsis aphrodite, pollen tubes entered the ovary within 3 days after pollination. Within 15 days, pollen tubes evenly spread throughout the placental cavities. Within 60 days after the pollination event, 30.6% of the tips of the pollen tubes started to enter the micropyles (i.e. entry points) of the ovules. Finally, 65 to 70 days after the pollination event, fertilisation occurred.