plastochronn.

Brit.

/ˈplastəkrɒn/, U.S.

/ˈplæstəˌkrɑn/

Forms: 1900s– plastochron, 1900s– plastochrone.

Origin: A borrowing from German. Etymon: German Plastochron.

Etymology: < German Plastochron (E. Askenasy 1878, in Verhandl. Naturhist.-Medic. Vereins zu Heidelberg 2 76) < ancient Greek πλαστός formed, moulded (see plastic n.) + χρόνος time (see chronic adj.).

Botany.

The interval of time between the initiation of leaf growth at two consecutive nodes in a growing shoot apex.

ΘΚΠ

the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > [noun] > parts of > stamen or pistil > stamen(s) > anther > interval between formations of leaves in

plastochron1929

1929 New Phytologist 28 41 These differences may partly be accounted for by the fact that an interval elapses—called by some authors the ‘plastochron’—between the initiation of successive primordia.

1938 J. H. Priestley & L. I. Scott Introd. Bot. xiii. 173 In the ²/ ₅ system it will be noted..that each primordium is three plastochrones removed from its one neighbour, two from the other.

1965 K. Esau Plant Anat. (ed. 2) v. 106 In Zea mays..the successive plastochrons in the embryo lengthen from 3.5 to 13.5 days, whereas those in the seedling shorten from 3.6 to 0.5 days.

1999 Internat. Jrnl. Plant Sci. 160 Suppl. 76/2 The median leaf trace extends acropetally into the ventral leaf primordium during the first plastochron of leaf development.

Compounds

plastochron index n. an index for measuring the developmental age of a shoot, based on the number of leaves that are not less than some stated length, plus a fractional adjustment so calculated that the value of the index changes smoothly as the shoot grows.

ΘΚΠ

the world > plants > botany > [noun] > ratio or index of development of shoots

plastochron ratio1948

plastochron index1955

1955 F. J. Michelini (title of Ph.D. diss., Univ. of Pennsylvania) The use of the plastochron index in studies of morphological and physiological development in Xanthium italicum Moretti.

1980 Sci. Amer. May 113/1 The plastochron index..is a continuous developmental scale that can be employed to draw conclusions indirectly about the growth of the apical meristem of the shoot..when direct observations are not feasible.

plastochron ratio n. the ratio between the length of successive leaves in the apex of a growing shoot.

ΘΚΠ

the world > plants > botany > [noun] > ratio or index of development of shoots

plastochron ratio1948

plastochron index1955

1948 F. J. Richards in Symp. Soc. Exper. Biol. 2 226 The differences between the various orders of phyllotaxis have been referred to differences in the ratio of the distances of two successive primordia from the apical centre... The ratio will be referred to as the ‘plastochrone ratio’.

1980 Sci. Amer. May 112/3 When the lengths of successive leaves are measured..it is found that the ratio of the length of a leaf to the length of the next-youngest one is reasonably constant for leaves that are growing rapidly. This relation can be called the plastochron ratio, and can be interpreted as the ratio by which a typical leaf increases in length per plastochron.

Derivatives

plastoˈchronic adj. of or relating to a plastochron or plastochrons.

ΘΚΠ

the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > [adjective] > having or relating to parts > of or having stamens or pistils > of or having stamens or male > of or having anthers and related parts > of interval between formations of leaves in

plastochronic1946

1946 Amer. Jrnl. Bot. 33 290 In the orderly plastochronic succession of young leaves, a transverse section just above the stem apex shows progressive stages of development in the successive leaf primordia.

1957 Amer. Jrnl. Bot. 44 302/1 Much would be gained by determining the precise plastochron age of each apex, rather than..judging the plastochronic phase subjectively.

1980 Sci. Amer. May 113/1 This plastochronic rhythm of growth processes that are repeated in time and displaced in space is characteristic of the growth of a shoot.

This entry has been updated (OED Third Edition, June 2006; most recently modified version published online March 2022).

单词	plastochron
释义	plastochronn. Brit. /ˈplastəkrɒn/, U.S. /ˈplæstəˌkrɑn/ Forms: 1900s– plastochron, 1900s– plastochrone. Origin: A borrowing from German. Etymon: German Plastochron. Etymology: < German Plastochron (E. Askenasy 1878, in Verhandl. Naturhist.-Medic. Vereins zu Heidelberg 2 76) < ancient Greek πλαστός formed, moulded (see plastic n.) + χρόνος time (see chronic adj.). Botany. The interval of time between the initiation of leaf growth at two consecutive nodes in a growing shoot apex. ΘΚΠ the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > [noun] > parts of > stamen or pistil > stamen(s) > anther > interval between formations of leaves in plastochron1929 1929 New Phytologist 28 41 These differences may partly be accounted for by the fact that an interval elapses—called by some authors the ‘plastochron’—between the initiation of successive primordia. 1938 J. H. Priestley & L. I. Scott Introd. Bot. xiii. 173 In the ²/ ₅ system it will be noted..that each primordium is three plastochrones removed from its one neighbour, two from the other. 1965 K. Esau Plant Anat. (ed. 2) v. 106 In Zea mays..the successive plastochrons in the embryo lengthen from 3.5 to 13.5 days, whereas those in the seedling shorten from 3.6 to 0.5 days. 1999 Internat. Jrnl. Plant Sci. 160 Suppl. 76/2 The median leaf trace extends acropetally into the ventral leaf primordium during the first plastochron of leaf development. Compounds plastochron index n. an index for measuring the developmental age of a shoot, based on the number of leaves that are not less than some stated length, plus a fractional adjustment so calculated that the value of the index changes smoothly as the shoot grows. ΘΚΠ the world > plants > botany > [noun] > ratio or index of development of shoots plastochron ratio1948 plastochron index1955 1955 F. J. Michelini (title of Ph.D. diss., Univ. of Pennsylvania) The use of the plastochron index in studies of morphological and physiological development in Xanthium italicum Moretti. 1980 Sci. Amer. May 113/1 The plastochron index..is a continuous developmental scale that can be employed to draw conclusions indirectly about the growth of the apical meristem of the shoot..when direct observations are not feasible. plastochron ratio n. the ratio between the length of successive leaves in the apex of a growing shoot. ΘΚΠ the world > plants > botany > [noun] > ratio or index of development of shoots plastochron ratio1948 plastochron index1955 1948 F. J. Richards in Symp. Soc. Exper. Biol. 2 226 The differences between the various orders of phyllotaxis have been referred to differences in the ratio of the distances of two successive primordia from the apical centre... The ratio will be referred to as the ‘plastochrone ratio’. 1980 Sci. Amer. May 112/3 When the lengths of successive leaves are measured..it is found that the ratio of the length of a leaf to the length of the next-youngest one is reasonably constant for leaves that are growing rapidly. This relation can be called the plastochron ratio, and can be interpreted as the ratio by which a typical leaf increases in length per plastochron. Derivatives plastoˈchronic adj. of or relating to a plastochron or plastochrons. ΘΚΠ the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > [adjective] > having or relating to parts > of or having stamens or pistils > of or having stamens or male > of or having anthers and related parts > of interval between formations of leaves in plastochronic1946 1946 Amer. Jrnl. Bot. 33 290 In the orderly plastochronic succession of young leaves, a transverse section just above the stem apex shows progressive stages of development in the successive leaf primordia. 1957 Amer. Jrnl. Bot. 44 302/1 Much would be gained by determining the precise plastochron age of each apex, rather than..judging the plastochronic phase subjectively. 1980 Sci. Amer. May 113/1 This plastochronic rhythm of growth processes that are repeated in time and displaced in space is characteristic of the growth of a shoot. This entry has been updated (OED Third Edition, June 2006; most recently modified version published online March 2022). < n.1929
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