Torus-Margo Pits Help Conifers Compete with Angiosperms
نویسندگان
چکیده
منابع مشابه
Torus-margo pits help conifers compete with angiosperms.
The unicellular conifer tracheid should have greater flow resistance per length (resistivity) than the multicellular angiosperm vessel, because its high-resistance end-walls are closer together. However, tracheids and vessels had comparable resistivities for the same diameter, despite tracheids being over 10 times shorter. End-wall pits of tracheids averaged 59 times lower flow resistance on an...
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because of slow growth rates caused by an inefficient transport system and low leaf photosynthetic capacity, gymnosperm seedlings are weak competitors with angiosperms in productive habitats. We measured component (shoot, leaf, and root) and whole-plant hydraulic conductances of sapling-sized tropical plants growing on nitrogen-poor white sand in Borneo. After accounting for size effects, there...
متن کاملPit membrane structure is highly variable and accounts for a major resistance to water flow through tracheid pits in stems and roots of two boreal conifer species.
The flow of xylem sap in conifers is strongly dependent on the presence of a low resistance path through bordered pits, particularly through the pores present in the margo of the pit membrane. A computational fluid dynamics approach was taken, solving the Navier-Stokes equation for models based on the geometry of pits observed in tracheids from stems and roots of Picea mariana (black spruce) an...
متن کاملAnalysis of circular bordered pit function II. Gymnosperm tracheids with torus-margo pit membranes.
A model of xylem conduit function was applied to gymnosperm tracheids with torus-margo pit membranes for comparison with angiosperm vessels. Tracheids from 17 gymnosperm tree species with circular bordered pits and air-seed pressures from 0.8 to 11.8 MPa were analyzed. Tracheids were more reinforced against implosion than vessels, consistent with their double function in transport and support. ...
متن کاملNew insights into the mechanisms of water-stress-induced cavitation in conifers.
Cavitation resistance is a key parameter to understand tree drought tolerance but little is known about the mechanisms of air entry into xylem conduits. For conifers three mechanisms have been proposed: (1) a rupture of pit margo microfibrils, (2) a displacement of the pit torus from its normal sealing position over the pit aperture, and (3) a rupture of an air-water menisci in a pore of the pi...
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ژورنال
عنوان ژورنال: Science
سال: 2005
ISSN: 0036-8075,1095-9203
DOI: 10.1126/science.1120479