| 单词 |
heliotropism |
| 释义 |
heliotropism Bot.|hiːlɪˈɒtrəʊpɪz(ə)m|
[mod. f. Gr. ἥλιος sun + -τροπος turning: see -ism. In F. héliotropisme (1832, De Candolle, Physiol. Végét. II. 844), mod.L. and Ger. heliotropismus.]
The property, exhibited by growing parts of plants, of bending or turning in a particular manner under the influence of light. The most usual case (to which some restrict the term) is that of bending towards the light (positive heliotropism); that of bending away from it is distinguished as negative heliotropism or apheliotropism; that of taking a direction at right angles to it, as transverse heliotropism or diaheliotropism.
1854Mayne Expos. Lex., Heliotropismus, term for that faculty by which certain plants constantly turn their flowers to the sun: heliotropism. 1875Bennett & Dyer Sachs' Bot. 677 Both positive and negative heliotropism occur not only in organs containing chlorophyll, but also in those that are colourless. Ibid. 775 The positive heliotropism of twining internodes is generally feeble. 1880Nature XXI. 438 The Electric Light..produced heliotropism in plants exposed to it. 1880C. & F. Darwin Movem. Pl. 5 Authors speak of positive and negative heliotropism..but it is much more convenient to confine the word heliotropism to bending towards the light. |
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