In
plant biology, the hyponastic response is a
nastic movement characterized by an upward bending of
leaves
A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
or other
plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
parts, resulting from accelerated growth of the lower side of the
petiole in comparison to its upper part. This can be observed in many terrestrial plants and is linked to the
plant hormone
Plant hormones (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis, the regulation of Organ (anat ...
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
.
The plant’s root senses the water excess and produces
1-Aminocyclopropane-1-carboxylic acid which then is converted into ethylene, regulating this process.
[(Manual interactivo de fisiología vegetal;Facultad de Agronomía;Montevideo)]
Submerged plants often show a hyponastic response, where the upward bending of the leaves and the elongation of the
petioles might help the plant to restore normal gas exchange with the atmosphere.
Plants that are exposed to elevated ethylene levels in experimental set-ups also show a hyponastic response.
References
Plant physiology
Botany
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