Afghanistan 1999 stamps Orchids/Flowers/Plants/Nature full set MNH

Afghanistan 1999 stamps Orchids/Flowers/Plants/Nature full set MNH**

Orchids represent one of the most diverse and highly evolved families of flowering plants, boasting a wide array of species with unique floral features such as morphology, color, size, and fragrance. These characteristics make orchids highly sought after in horticultural markets as potted plants and cut flowers. The process of orchid flowering is influenced by both environmental signals like temperature and internal developmental programs controlled by genetic factors, similar to many other flowering plant species.

Understanding the molecular mechanisms underlying orchid floral transition and flower development has been greatly enhanced by advancements in molecular and genetic technologies. Researchers have focused on commercially important orchid species such as Phalaenopsis, Dendrobium, and Oncidium to unravel the genetic networks and representative genes involved in floral transition and flower development.

The flowering of orchids can be divided into two main steps: floral transition and flower development. Floral transition is influenced by factors like juvenility, temperature, and photoperiod, which determine when orchids initiate flowering in relation to their ontogeny and the season. Molecular studies in model plants like Arabidopsis and rice have shed light on the genetic mechanisms underlying floral transition, but orchid flowering remains less understood.

Once flowering is initiated, specific genes known as flowering time genes regulate the transition from vegetative meristem to floral meristem. Subsequently, floral meristem identity genes govern flower formation, while cadastral genes regulate the formation of floral whorls. Homeotic genes play a role in determining the structure and position of floral organs within the whorls. Despite the diverse floral morphology found in orchids and other flowering plants, the establishment and maintenance of floral organ specification are governed by an interactive network of MADS-box transcription factors, as explained by the ABCDE model primarily based on studies in Arabidopsis.

Orchids exhibit remarkable adaptability and can thrive in a wide range of environments, spanning from sea level to elevations as high as 4,600 meters (15,000 feet). However, the highest diversity of orchid species is typically found in cloud-forest habitats in tropical regions.

Cloud forests are characterized by their unique atmospheric conditions, where clouds envelop the mountain slopes day and night. These forests are often situated on mountainsides, allowing clouds to brush against them regularly. As a result, these environments are characterized by high humidity and moisture levels.

The dense vegetation in cloud forests, including mosses and lichens, contributes to the high humidity levels. Additionally, the inclination of the ground allows sunlight to penetrate through the canopy, reaching the forest floor. This combination of factors creates a perfect habitat for a variety of plants, including epiphytic orchids, members of the Gesneriaceae and Araceae families, ferns, and numerous other epiphytic species.

Epiphytic orchids, in particular, thrive in cloud-forest environments. These orchids have adapted to grow on other plants or surfaces without being parasitic, using their specialized roots to absorb water and nutrients from the air and surrounding debris. The abundance of moisture and filtered sunlight in cloud forests provides optimal conditions for orchids and other epiphytes to grow and flourish.