Effects of sheath tube length on leaf development in perennial ryegrass (Lolium perenne L.)

Abstract

Position in and contribution of leaf laminae to the canopy of forage grasses are important both in determining herbage growth rates and intake rate by grazing animals. These canopy characteristics are controlled by the way dry matter is apportioned between sheath and lamina in growing leaves. The objective of this work was to determine how the development of individual leaves is affected by altering the effective length of the psuedostem tube, on the assumption that the light environment within the tube varied. The development of a leaf from initiation at the apex to maturity was followed by successive destructive dissections of tillers. Vertical incisions were made in the pseudostem of each tiller to three different depths. The three treatments imposed wereno incision (control), moderate and severe incision of the sheath length. Destructive harvests of tillers followed 3, 6, 12 and 24 days after imposition of treatments. Incision resulted in the length of the monitored leaf being reduced significantly at all harvests, and differentiation of the sheath beginning earlier. The length reduction reflected a reduction in both cell size and cell number and the effects were evident at the earliest harvest. The data support the theory that leaf size and timing of onset of sheath development are influenced by the environment of the developing leaf. The present results indicate that sheath tube length affects leaf development and suggests that the effects are substantially explained by a direct light effect on the location and depth of the elongation zone.

Defoliation, Shoot Plasticity, Sward Structure and Herbage Utilization in Pasture: Review of the Underlying Ecophysiological Processes

“…The physiological determinants are more obscure for LED than for LER. Several earlier studies have indicated that the sheath length of a mature leaf affects the final length of the following subtended leaf, and reduction in sheath tube length due to defoliation was the cause of the reduction in leaf length [47,64,102,103]. These studies suggest that the decrease in leaf length was associated with a decrease in LED.…”

Leaf Length Variation in Perennial Forage Grasses

“…It appears that these cellular processes are under the influence of the length of the enclosing sheaths both directly and indirectly. Experimental modifications to incise or artificially increase the pseudostem tube length directly affected the length of the leaf elongation zone and the final length of the cells [63,64]. Furthermore, modification of the pseudostem tube length with, for example, an opaque plastic tube, could also indirectly affect cell dynamics via control of the timing of leaf tip emergence [65].…”

“…Furthermore, modification of the pseudostem tube length with, for example, an opaque plastic tube, could also indirectly affect cell dynamics via control of the timing of leaf tip emergence [65]. Delaying or anticipating this event could modify both the placement of the sheath-blade boundary and the total cell number, as cessation of cell division at the base of the leaf could be triggered at the moment of leaf tip emergence from the previous sheath [63,64]. These effects may be light mediated.…”

“…Nevertheless, this trait displays high plasticity that could be mediated by self-regulatory processes. Thus, leaf length is directly affected by the sheath length of the preceding leaf on the same tiller [61,63,64] in a sort of recursive loop ( Figure 5). These concepts were integrated into a cybernetic framework [66].…”

Effects of Nitrogen Levels on Anatomy, Growth, and Chlorophyll Content in Sunflower (Helianthus annuus L.) Leaves

“…However, 60 kg N ha -1 extended epidermal cell size but number of photosynthetic cells were reduced in comparison to control leaf. Longer leaves and carbon partitioning in cell wall contents has been reported in grasses (Casey et al, 1999). The leaf size and weight relationship may discard the incorporation of nitrogen into protein thereby diverting into the structural components of leaf, cell walls and new cell formation in the lower epidermis to provide the support at the horizontal axis of stem with increasing supply of nitrogen.…”