Although cavitation and refilling cycles could be common in plants, it is unknown whether these cycles weaken the cavitation resistance of xylem. Stem or petiole segments were tested for cavitation resistance before and after a controlled cavitation-refilling cycle. Cavitation was induced by centrifugation, air drying of shoots, or soil drought. Except for droughted plants, material was not sig...

Recent work has suggested that the large earlywood vessels of ring-porous trees can be extraordinarily vulnerable to cavitation making it necessary that these trees maintain a consistent and favorable water status. We compared cavitation resistance, vessel refilling, transport capacity and water status in a study of ring-porous Quercus gambelii Nutt. (oak) and diffuse-porous Acer grandidentatum...

For terrestrial plants, maintenance of the integrity of the rootto-leaf water transport pathway is essential for sustaining photosynthetic 9as exchange and growth. The problem of maintaining long-distance water transport is especially challengin9 in trees because path-length resistances and gravity can result in steep gradients of increasing xylem tension from roots to terminal branches, potent...

In higher plants the pH of the xylem sap plays an important role in drought signaling, growth regulation, and plant nutrition. However, the interpretation of the data is very controversial. The main reason for this is that the xylem pH in intact plants was not directly accessible hitherto. We present here a novel, minimally-invasive probe based on the xylem pressure-potential probe (used for me...

The xylem vessels of trees constitute a model natural microfluidic system. In this work, we have studied the mechanism of air flow in the Populus xylem. The vessel microstructure was characterized by optical microscopy, transmission electronic microscopy (TEM), and atomic force microscopy (AFM) at different length scales. The xylem vessels have length ≈15 cm and diameter ≈20μm. Flow from one ve...

changes during shrinkage, aquaporin activity and/or changes in the vapor phase transport. The application of models calibrated with anatomy will be an essential approach to determining the drivers of K ox decline. Finally, speculation that K ox decline may protect the xylem in the leaf and throughout the rest of the plant from tensions that induce embolism needs to be validated using models and...

Experiments were conducted to test whether the facultatively phytophagous predator Orius insidiosus (Say) (Heteroptera: Anthocoridae) ingested phloem, xylem or mesophyll contents from soybean plants (Glycine max L.). Potential uptake of phloem sap was examined by radiolabeling photosynthate with CO2 and then measuring the accumulation of radiolabeled metabolites in feeding animals. Most O. insi...

A temperature-dependent xylem occlusion was found in cut chrysanthemum stems (Dendranthema grandiflora, cv. Viking) which were placed for 24 h in air at 5°C prior to vase life evaluation. The response was inhibited by a 5-h treatment, prior to placement in air, with aqueous solutions at low initial pH or solutions containing near-neutral antioxidants (n-propylgallate, phloroglucinol, butylated ...

Recent work suggests that hydraulic mechanisms, rather than cambium necrosis, may account for rapid post-fire tree mortality. We experimentally tested for xylem cavitation, as a result of exposure to high-vapour-deficit (D) heat plumes, and permanent xylem deformation, as a result of thermal softening of lignin, in two tree species differing in fire tolerance. We measured percentage loss of con...

The effects of time, rate of the water flow, and ambient pH on centripetal passage of radiophosphorus across intact bean roots to the xylem were studied. Isotope which completed passage and entered the xylem stream, as well as amounts delivered to the plant top, served to measure centripetal passage.Centripetal passage of radiophosphorus increased parabolically reaching a maximum after 1 hr and...