HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Cobb, A. R. Articles by Holbrook, N. M. Search for Related Content PubMed Articles by Cobb, A. R. Articles by Holbrook, N. M. Agricola Articles by Cobb, A. R. Articles by Holbrook, N. M.

Dynamics of freeze–thaw embolism in Smilax rotundifolia (Smilacaceae)¹

²Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138 USA; ³Department of Viticulture & Enology, University of California, One Shields Avenue, Davis, California 95616 USA

ABSTRACT

Freeze–thaw cycles pose a major physiological challenge for all temperate perennial plants, but monocotyledonous vines face a still greater risk because their few large vessels are especially susceptible to embolism and are not replaced by secondary growth. The genus Smilax is particularly remarkable because it is widespread in the tropics but includes species that survive the hard frosts of New England winters. Smilax rotundifolia was monitored for a year for evidence of stem xylem freeze–thaw cavitation and refilling. Embolism of metaxylem was complete by late November and was completely reversed by late April, when root pressures rose as high as 100 kPa. Protoxylem remained full of sap throughout the year in cryogenic scanning electron micrographs. Three methods were used to quantify embolism: percent loss conductivity (PLC), gravimetric air fraction (GAF: mass of water in stem xylem relative to capacity), and cryogenic scanning electron microscopy (cryo-SEM). The three methods corroborated one another well and gave quantitatively similar results. Osmolality of xylem sap extracted from exuding stems was 64 mol/kg (±7.0, N = 8), consistent with the root pressures observed. Strong root pressure can account for Smilax's survival in temperate regions with severe frosts, where few monocots with persistent aboveground organs are found.

Key Words: Bedford, Massachusetts • cryo-SEM • embolism reversal • gravimetric air fraction • percent loss conductivity • root pressure • Smilacaceae • vine