Hollow Stems in Amaryllis belladonna

August 30, 2022

Menashe_Stems

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Photographer: Menashe Davidson menashe.davidson@gmail.com

Summary Author: Menashe Davidson menashe.davidson@gmail.com

While in my home-garden (in Rishon LeZion, Israel), I observed the erect hollow leafless stems of Amaryllis belladonna plant, also known as the Amaryllis lily and the August lily. Carrying inflorescences they bear showy funnel-shaped flowers (1st photo). I questioned the purpose of why there are hollow stems in some plants. Stems of course provide a transport system, mechanical support, and a primary growth point for plant. They also improve the presentation of the plant’s sexual organs, thereby increasing the plant's chance of reproduction.

The common misconception was to believe that the hollow stem is solely for nutrient or water transport. But when I cut the stem in various heights, I learned that the hollow stem holds water only in the bottom 4 or 5 inches (12 cm) -- most of the stem contains air (2nd photo).  

Scientists In University of Guelph (Ontario) studied differences in plant stem type, and how effectively they regulate their temperature. They found that the stem lumen (hollow portion of the stem) allows the plant to maintain a distinct internal microclimate and in the present of sunlight, the temperature in the lumen was slightly above that of the ambient air. Increases in temperature encourages growth of sexual organs in plants, which in turn helps the flower to develop quickly, becoming more prominent to pollinators. And this effect is exactly what I observed in Amaryllis flowers. (Below)

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Rishon LeZion, Israel Coordinates: 31.9730, 34.7925

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