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Changes in root hydraulic conductivity for two tropical epiphytic cacti as soil moisture varies
Author(s) -
North Gretchen B.,
Nobel Park S.
Publication year - 1994
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1994.tb15407.x
Subject(s) - xylem , desiccation , hydraulic conductivity , mucilage , epiphyte , biology , water content , transpiration , botany , water transport , horticulture , soil water , agronomy , soil science , environmental science , ecology , water flow , photosynthesis , geotechnical engineering , engineering
The tropical epiphytic cacti Epiphyllum phyllanthus and Rhipsalis baccifera experience extreme variations in soil moisture due to limited soil volumes and episodic rainfalls. To examine possible root rectification, whereby water uptake from a wet soil occurs readily but water loss to a dry soil is minimal, responses of root hydraulic conductivity (L p ) to soil drying and rewetting were investigated along with the underlying anatomical changes. After 30 d of soil drying, L p decreased 50%–70% for roots of both species, primarily because increased suberization of the periderm reduced radial conductivity. Sheaths composed of soil particles, root hairs, and mucilage covered young roots and helped reduce root desiccation. Axial (xylem) conductance increased during drying due to vessel differentiation and maturation, and drought‐induced embolism was relatively low. Within 4 d of rewetting, L p for roots of both species attained predrought values; radial conductivity increased for young roots due to the growth of new branch roots initiated during drying and for older roots due to the development of radial breaks in the periderm. The decreases in L p during drought reduced plant water loss to a dry soil, and yet maximal water uptake and transpiration occurred within a few days of rewetting, helping these epiphytes to take advantage of episodic rainfalls in a moist tropical forest.