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Effect of Root Cooling on Photosynthesis of Artemisia tridentata Seedlings under Different Light Levels
Author(s) -
BassiriRad H.,
Caldwell M. M.,
Mott K. A.
Publication year - 1993
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1993.tb00744.x
Subject(s) - photosynthesis , stomatal conductance , shoot , chemistry , respiration , horticulture , water content , botany , respiration rate , agronomy , biology , geotechnical engineering , engineering
Abstract Root chilling has been shown to inhibit shoot photosynthesis yet the mechanism for such an action is not clearly understood. A study was designed to elucidate the mechanism by which root cooling may affect net photosynthesis. Roots of Artemisia tridentata seedlings were cooled from 20°C to 5°C while their shoot temperature remained at 20°C. This was conducted at two light levels (700 and 1300 μmol m −2 s −1 ). The time course of shoot net photosynthesis (A), stomatal conductance to water vapor (g s ), intercellular CO 2 concentration (C i ) and root respiration (R s ) were determined on a whole‐plant basis. Root cooling caused a 25% reduction in A at high PPFD, which was preceded by more than 50% reduction of g s and about 10% reduction in C i . A versus C i curves for single branches showed no difference between cold and warm soil temperatures, although stomatal conductance was lower for the lower soil temperature. This suggests that a stomatal limitation may have been involved in the inhibition of A. Furthermore, a concomitant decrease of as much as 23% in leaf relative water content (RWC) indicated that root cooling affected stomatal closure due to decreased water supply to the foliage. At lower PPFD, root cooling did not cause a decrease in A of the whole plant despite a moderate drop in g s , C i and RWC. Cold soil also led to a substantial and rapid reduction in root respiration rate (R s ) regardless of the light level.