Anatomical and physiological characteristics of the petiole of Abutilon theophrasti in relation to circadian leaf movements

Abstract

W. L. 1981. Anatomical and physiological characteristics of the petiole of Abutilon theophrasti in relation to circadian leaf movements. -Physiol. Plant. 51: 309-313.Leaf movements in Abutilon theophrasti Medic, were monitored manually and by a continuous electronic recording device. Plants entrained to a daily regime of a 15 h light span followed by 9 h of darkness showed rhythmic movements that persisted under conditions of continuous illumination and constant temperature with a circadian period. The rhythmic change in orientation of the leaf from a near horizontal (day) to a near vertical (night) position was attributed to movement of the blade and not the petiole. The end of the petiole next to the blade functions as a joint or pulvinus. Anatomical confirmation of the existence of a pulvinus in the Abutilon leaf was provided by light microscopy. Vascular tissue in this region forms a solid cylinder with no pith, and the cortex is parenchymatous. In the main part of the petiole, the vascular tissue is arranged in four to six bundles, a pith is present, and the cortex contains a sub-epidermal ring of collenchyma. Both the functional and anatomical evidence indicate the presence of a pulvinus that functions in circadian leaf movements of Abutilon,

Leaf movements and their relationship with the lunisolar gravitational force

“…80 % increase in cell elongation in the first millimetre of the abaxial petiole (Rauf et al, 2013). In some types of nonarticulated leaves, although there may be no external indication of a distinct articulation at the proximal zone of the petiole, nevertheless they may have a zone with a particular vascular anatomy which facilitates movement of the lamina, such as was described for the photonastic leaves of Malva neglecta (Yin, 1938) and of Abutilon theophrasti (Fuhrman and Koukkari, 1981).…”

Compensatory Responses of Common Cocklebur (Xanthium strumarium) and Velvetleaf (Abutilon theophrasti) to Partial Shading

“…Of particular interest is the pronounced change in upper leaf angle observed in velvetleaf when lower leaves were shaded. Velvetleaf exhibits circadian leaf movements, with leaves held horizontally during the day and vertically at night (8). Movement of velvetleaf leaves is by means of a pulvinus at the junction of the petiole with the leaf blade (8).…”

“…Velvetleaf exhibits circadian leaf movements, with leaves held horizontally during the day and vertically at night (8). Movement of velvetleaf leaves is by means of a pulvinus at the junction of the petiole with the leaf blade (8). A change in leaf angle such that the leaf is held in a position more perpendicular to the light source increases total light interception by the leaf, thereby increasing photosynthesis for light levels below saturation (13).…”