natural, renewable, biodegradable and low pollution hemp fibers are an alternative to trees xylem and artificial fibers. in this study, xylem and bast fiber properties of six iranian hemp populations including length, width, wall thickness, lumen width and wall index were measured and compared. to this purpose, collected population seeds from different parts of iran were nursed in a controlled ...

Temporal and spatial patterns of stem and root radius changes were continuously measured on mature, subalpine Norway spruce (Picea abies (L.) Karst.) over 2 years. In addition, freezing experiments with stem segments of saplings were carried out in a climate chamber. The dynamics of the radius fluctuations were analyzed in relation to temperature profiles of air, bark, and soil. We found that b...

The vulnerability of plant water transport tissues to a loss of function by cavitation during water stress is a key indicator of the survival capabilities of plant species during drought. Quantifying this important metric has been greatly advanced by noninvasive techniques that allow embolisms to be viewed directly in the vascular system. Here, we present a new method for evaluating the spatial...

the vase life of cut flowers and foliage is often shortened by vascular occlusions that constrict vase solution supply. reduction in stem conductivity is typically caused by blockage of cut stem ends and xylem conduits by microbes, physiological plugging, and disruption of water columns in xylem vessels by cavitations and air emboli. cut flower and foliage longevity can be greatly affected by t...

The vascular system is organized throughout the plant body for transporting water, nutrients, and signaling molecules. During vascular development, xylem, phloem, and procambial/cambial cells are produced in a spatiotemporally organized manner. Several key regulators for xylem cell patterning and differentiation have been discovered, including auxin, cytokinin, CLE peptides, microRNAs, HD-ZIPII...

Progressive diebacks of outer canopy branchlets of Ceanothus crassifolius were repeatedly observed after rainless periods up to 9 mo in duration in the Santa Monica Mountains of southern California. Mean xylem pressures of branchlets near the end of drought were as low as -11.2 MPa (N = 22) with a mean of about 60 dead branchlets per shrub. Inoculation (N = 15) with three species of fungi previ...

This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering...

Calcium (Ca) uptake into fruit and leaves is dependent on xylemic water movement, and hence presumably driven by transpiration and growth. High leaf transpiration is thought to restrict Ca movement to low-transpiring tomato fruit, which may increase fruit susceptibility to the Ca-deficiency disorder, blossom end rot (BER). The objective of this study was to analyse the effect of reduced leaf tr...

Despite renewed interest in the nature of limitations on maximum tree height, the mechanisms governing ultimate and species-specific height limits are not yet understood, but they likely involve water transport dynamics. Tall trees experience increased risk of xylem embolism from air-seeding because tension in their water column increases with height because of path-length resistance and gravit...

This review emphasizes recent developments and controversies related to the uptake, transport and loss of water by trees. Comparisons of the stable isotope composition of soil and xylem water have provided new and sometimes unexpected insights concerning spatial and temporal partitioning of soil water by roots. Passive, hydraulic redistribution of water from moister to drier portions of the soi...