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Gaseous Exchange of Simmondsia chinensis (Jojoba) Measured with a Double Isotope Porometer and Related to Water Stress, Salt Stress, and Nitrogen Deficiency 1
Author(s) -
Adams J. A.,
Johnson H. B.,
Bingham F. T.,
Yermanos D. M.
Publication year - 1977
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1977.0011183x001700010004x
Subject(s) - transpiration , xylem , nitrogen fixation , stomatal conductance , photosynthesis , osmotic pressure , botany , biology , horticulture , conductance , nitrogen , salinity , chemistry , ecology , mathematics , organic chemistry , combinatorics
Gaseous exchange of Simmondsia chinensis [(Link) Schneider] (a desert shrub which may provide a substitute for sperm whale oil) was studied by exposing leaves simultaneously to radioisotopes of water ( 3 HHO) and CO 2 ( 14 CO 2 ) to determine conductances to water vapor and total conductances to CO 2 assimilation, respectively. Fixation rates of CO 2 and mesophyll conductances to CO 2 were calculated. Leaf conductance to water vapor and CO 2 fixation rates decreased markedly only at very low values of soil‐water and leaf‐xylem pressure potentials and recovered to maximum values after having been subjected to soil water potentials below ‐‐40 bars, indicating the extreme drought tolerance of S. chinensis . The ratios ofconductance to CO 2conductance to H 2 Oincreased as water stress became more intense, suggesting that transpiration was reduced relatively more than photosynthesis, which could have considerable value under drought stress. Plants under intense water stress generally had little or no reduction in mesophyll conductance to CO 2 . There was no significant decrease in conductance to water vapor, CO 2 fixation rate, or mesophyll conductance to CO 2 with increasing salinity down to root medium osmotic potentials as low as —9 bars. This is consistent with the reported high salt tolerance of S. chinensis . Nitrogen‐deficient plants had significant reductions in CO 2 fixation rate and mesophyll conductance to CO 2 but not in conductance to water vapor.