Bimodal pattern of allometric scaling along grapevine shoots.

Background And Aims: Each branch internode, with the organs growing on it, can be seen as a single morphological phytomer subunit made of structurally and functionally interrelated components. However, allometric relationships between the anatomy and morphology of these subunits remain unclear, particularly in the axial context. The aim of this study was to address this knowledge gap by measuring morpho-anatomical parameters and their allometric relationships along grapevine shoots.

Rapid leaf xylem acclimation diminishes the chances of embolism in grapevines.

Under most conditions tight stomatal regulation in grapevines (Vitis vinifera) avoids xylem embolism. The current study evaluated grapevine responses to challenging scenarios that might lead to leaf embolism and consequential leaf damage. We hypothesized that embolism would occur if the vines experienced low xylem water potential (Ψx) shortly after bud break or later in the season under a combination of extreme drought and heat.

Seasonal adjustment of leaf embolism resistance and its importance for hydraulic safety in deciduous trees.

Embolism resistance is often viewed as seasonally stable. Here we examined the seasonality in the leaf xylem vulnerability curve (VC) and turgor loss point (Ψ ) of nine deciduous species that originated from Mediterranean, temperate, tropical, or sub-tropical habitats and were growing on the Volcani campus, Israel. All four Mediterranean/temperate species exhibited a shift of their VC to lower xylem pressures (Ψ ) along the dry season, in addition to two of the five tropical/sub-tropical species.

Productivity versus drought adaptation in olive leaves: Comparison of water relations in a modern versus a traditional cultivar.

The physiological traits that set the tradeoff between productivity and drought adaptation in plants are still under debate. To reveal these traits, we compared the water relations of two olive (Olea europaea) cultivars: "Barnea"-a highly productive modern cultivar; and "Souri"-a drought-adapted traditional cultivar. We hypothesized that Souri has lower hydraulic conductivity and lower hydraulic vulnerability.

An increase in xylem embolism resistance of grapevine leaves during the growing season is coordinated with stomatal regulation, turgor loss point and intervessel pit membranes.

Although xylem embolism resistance is traditionally considered as static, we hypothesized that in grapevine (Vitis vinifera) leaf xylem becomes more embolism-resistant over the growing season. We evaluated xylem architecture, turgor loss point (Ψ ) and water potentials leading to 25% of maximal stomatal conductance (g ) or 50% embolism in the leaf xylem (P ) in three irrigation treatments and at three time points during the growing season, while separating the effects of leaf age and time of season. Hydraulic traits acclimated over the growing season in a coordinated manner.

Shoot stem cell specification in roots by the WUSCHEL transcription factor.

The WUSCHEL homeobox transcription factor is required to specify stem-cell identity at the shoot apical meristem and its ectopic expression is sufficient to induce de novo shoot meristem formation. Yet, the manner by which WUS promotes stem-cell fate is not yet fully understood. In the present research we address this question by inducing WUS function outside of its domain.