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Changes in root hydraulic conductance (KR) of Olea oleaster seedlings following drought stress and irrigation

Published online by Cambridge University Press:  01 September 1998

MARIA A. LO GULLO ,
ANDREA NARDINI ,
SEBASTIANO SALLEO  and
MELVIN T. TYREE
MARIA A. LO GULLO
Affiliation:
Istituto di Botanica, Università di Messina C.P. 58, I-98166, Messina, S. Agata, Italy
ANDREA NARDINI
Affiliation:
Dipartimento di Biologia, Università di Trieste, via L. Giorgieri 10, I-34127, Trieste, Italy
SEBASTIANO SALLEO
Affiliation:
Dipartimento di Biologia, Università di Trieste, via L. Giorgieri 10, I-34127, Trieste, Italy
MELVIN T. TYREE
Affiliation:
USDA Forest Service, Northeastern Experiment Station, 705 Spear Street, Burlington, VT 05402-0968, USA
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Abstract

Quasi-steady-state measurements of root hydraulic conductance (KR) of Olea oleaster Hoffmgg. et Link potted seedlings were performed using a pressure chamber with the aim of: (a) measuring the impact of different water-stress levels on a KR; (b) measuring the kinetics of KR recovery several days after soil rewetting; (c) relating changes in KR to changes in root anatomy and morphology. Increasing water-stress was applied in terms of ratio of leaf water potential (ΨL) measured at midday to that at zero turgor (ΨTLP), i.e. ΨL/ΨTLP=0·5, 1·0, 1·2, 1·6; KR was measured initially and at 24, 48, 72, 96 h after irrigation.

Values of KR in seedlings stressed to ΨL/ΨTLP=1·2 increased for 48 h after irrigation from 0·23 to 0·97×10−5 kg s−1 m−2 MPa−1 i.e. from 16% to 66% of that measured in unstressed seedlings. A marked shift of the x-axis intercept of the straight line relating flow to pressure (zero flow at non-zero pressure) was recorded initially after irrigation and persisted up to 48 h. Recovery of KR occurred within 24 h after irrigation in seedlings at ΨL/ΨTLP=0·5 and 48 h later in those at ΨL/ΨTLP=1·0.

Severe drought stress (ΨL/ΨTLP=1·6) caused anatomical changes to roots which formed a two-layered exodermis with thicker suberized walls and a three- to four-layered endodermis with completely suberized tangential walls. Recovery of KR in these roots required resumed growth of root tips and emergence of new lateral roots.

Keywords

Root hydraulic conductancepressure chamberwater stress
Type
Research Article
Information
The New Phytologist , Volume 140 , Issue 1 , September 1998 , pp. 25 - 31
Copyright
© Trustees of New Phytologist 1998

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