Koller, D. (The Hebrew U., Jerusalem.2) Preconditioning of germination in lettuce at time of fruit ripening. Amer. Jour. Bot. 49(8): 841–844. 1962.—The effects of controlled environments during maturation on subsequent germination response of the seed were investigated with the light‐sensitive lettuce ‘Grand Rapids.‘ The plants matured under a variety of temperature/photoperiod combinations, after completing vegetative growth and flower initiation under identical conditions. Good seed set was obtained only at night temperatures between 17 and 23 C, under short‐day (8‐hr) conditions. Seed germination was tested at 20, 23 and 26 C, in continuous dark and after a light‐break, respectively. The conditions under which the seed had ripened brought about quantitative changes in the germination response. The stimulating effects of a light‐break on germination at high temperatures did not change, but maturation under high temperatures or in continuous light increased the high‐temperature tolerance of seed germination both in continuous dark and after a short light‐break.
Abslract-The palmatcly-compound leaf lamina o f Lupirius pulaesrinnc Hoiss. tracks the sun by independent diaphototropic movements of its individual leaflets. operated hy the appropriate flcxing o f their pulvinules. The lamina also exhibits two additional. light-dependent nastic movements, that can operate concurrently with the diaphototropic response: (1) a nyctinastic response to lightidark transitions by which all the leaflets fold down simultaneously and at equal rates. and which is reversed by a photonastic response to darkilight transitions by which all the leaflets unfold into a co-planar configuration;(2) 21 photonastic upward folding (*.cupping"), which all the leaflets exhibit simultaneously and at equal rates in response to high irradiance. thereby modulating their diaphototropic response to reduce light interception and evade over-exposure. Although the individual leaflets canx n s c all these light-signals and respond to them independently, they do so simultaneously. so that the entire lamina responds in a co-ordinated manner, as a unit. The photoreceptors for the two nastic responscs arc localized in the individual pulvinules and may or may not be the same. The photorcceptorc for thc diaphototropic perception are localized in thc proximal segmcnt of the lamina o f the individual Icaflets. adjacent to but outside the pulvinule. The separation of the sites o l perception for the tropic and nastic responses allows these responses to operate concurrently. The capacity of the diaphototropic rcsponsc to occur concurrently with one or the other of the two nastic responses may bc accounted for by its inductive nature 187
Koller, D. (Hebrew U., Jerusalem, Israel), H. R. Highkin, and O. H. Caso. Effects of gibberellic acid on stem apices of vernalizable grasses. Amer. Jour. Bot. 47(6) : 518–524. Illus. 1960.—Gibberellic acid was found to have distinct morphogenic effects on the stem apices of 3 vernalizable but unvernalized grasses: Hordeum vulgare var. ‘Kentucky,’ Hordeum bulbosum and Secale cereale var. ‘Winter Petkus.’ In these 3 species, GA caused the activation of lateral meristems on the embryonic nodes of the stem apices, under both short‐ and long‐day conditions. These lateral meristems differentiated into either flower primordia or vegetative shoots. The flower primordia developed almost invariably in Hordeum, while in Secale they seldom did, the apical meristem usually resuming normal vegetative growth after treatment. Despite the occurrence of flowering, it is concluded that the role of GA in this phenomenon is restricted to the activation of lateral meristems in the apex.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.