Volume : III, Issue : XII, December - 2014

Physiology of Temperate and Tropical Orchids–An Overview

L. C. De, N. Sailo, Deepak Rai

Abstract :

Epiphytic orchids are characterized by thick and succulent leaves with thick cell walls, cuticles and small substomatal chamber whereas those of terrestrial species are thin. Usually mature leaves are photosynthetically active. The base of the stem of sympodial epiphytes, or in some species essentially the entire stem, may be thickened to form what is called a pseudobulb that contains nutrients and water for drier periods. Terrestrial orchids may be rhizomatous or form corms or tubers which contain reserve carbohydrates. A marked increase in respiration following pollination has been observed in orchids. Activities of a number of enzymes like catalase, peroxidase, polyphenol oxidase, ascorbic acid oxidase and glycolic acid oxidase increased following pollination. All orchid species are mycoheterotrophic during germination and reliant upon fungi to complete their lifecycle. All thin leaved orchids fix CO2 via C3 pathway. C4 pathway occurs primarily in plants of tropical origin growing under high light and high temperature conditions, E.g, Arundina graminifolia. The majority of plants in the Orchid family uses Crassulacean Acid Metabolism or CAM photosynthesis to fixate carbon dioxide. In these plants, the carboxylating enzyme for dark fixation is phosphoenolpyruvate carboxylase (PEPCase). An orchid leaf will have greater rates of photosynthesis at higher levels of atmospheric CO2 concentration. In Cymbidium, the process from flower bud induction in the new growth to blooming can be divided into three stages, Flower Bud Initiation in the New Growth (Stage I), Flower Spike Initiation (Stage II) and Spike Elongation and Blooming (Stage III). Orchid pseudobulbs serve as water storage, carbohydrate storage and mineral storage organ.

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Article: Download PDF   DOI : 10.36106/ijsr  

Cite This Article:

L.C. De, N. Sailo, Deepak Rai Physiology of Temperate and Tropical Orchids-An Overview International Journal of Scientific Research, Vol : 3, Issue : 12 December 2014

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