Hypocotyl

(redirected from Mesocotyl)
Also found in: Dictionary, Medical.
Related to Mesocotyl: epicotyl

hypocotyl

[′hī·pə‚käd·əl]
(botany)
The portion of the embryonic plant axis below the cotyledon.

Hypocotyl

 

in sprouting plants, the section of the stem extending from the root collar (the zone between the main stem and the root) to the place of attachment of the cotyledons. In the embryo, the hopocotyl is the rudimentary stem. The sprouts of some plants have an elongate hypocotyl that bears assimilative cotyledons. This type of aboveground germination characterizes hornbeam. In other plants the hypocotyl is underdeveloped, and the cotyledons do not appear on the surface. Such underground germination is typical of the pea and the oak.

The anatomical structure of the hypocotyl retains its embryonic character. It may give rise to adventitious shoots, roots, or leaves (when the apex of the epicotyl is removed, as in cyclamen). In some plants the hypocotyl becomes the repository of nutrients (for example, the tuber in cyclamen). In many root crops, including the turnip, carrot, and sugar beet, the hypocotyl consists of the fleshy part of the storage organ, which is found between the stem base and the root proper.

L. V. KUDRIASHOV

References in periodicals archive ?
Key words: Garlic chive, mesocotyl axis, in vitro, micropropagation, rooting, acclimatization.
Phytoalexin synthesis by the sorghum mesocotyl in response to infection by pathogenic and nonpathogenic fungi.
In darkness, the coleoptile of LC germplasm was longer than that of EC germplasm, and the mesocotyl was shorter than that of EC germplasm.
Ten embryonic axes from samples preconditioned for 0, 24, and 48 h were excised and cut into three sections: mesocotyl, shoot, and radicle.
In the first phase, the relatively small coleoptile of panicoid seedlings is pushed to the soil surface by elongation of the mesocotyl (Ries and Hofmann, 1991) [sometimes called the subcoleoptile internode (Hyder et al., 1971)].
Briefly these criteria are (i) the tap root is the first root to emerge from the seed, (it) basal roots originate from the base of the hypocotyl or mesocotyl (frequently termed seminal roots in monocotylede not, s plants), and (iii) lateral roots are branches off of other roots (Fig.
Briefly these criteria are (i) the tap root is the first root to emerge from the seed, (ii) basal roots originate from the base of the hypocotyl or mesocotyl (frequently termed seminal roots in monocotyledenous plants), and (ii) lateral roots are branches off of other roots (Fig.
However, direct bombardment of oat immature embryos would be impractical because callus initiation arises from the mesocotyl of the immature embryo (Rines and McCoy, 1981; Bregitzer et al., 1989; 1995), a very small target for microprojectile bombardment.
Phenylalanine ammonia-lyase and hydroxy cinnamate: CoA ligase in maize mesocotyls inoculated with Helminthosporium maydis or Helminthosporium carbonum.
Changes in isozyme profiles of catalase, peroxidase and glutathione reductase during acclimation to chilling in mesocotyls of maize seedlings.