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Water Efficiency of Cassava. II. Differing Sensitivity of Stomata to Air Humidity in Cassava and Other Warm‐Climate Species 1
Author(s) -
ElSharkawy Mabrouk A.,
Cock James H.,
Held K. Alexander A.
Publication year - 1984
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/cropsci1984.0011183x002400030018x
Subject(s) - andropogon , biology , water use efficiency , stomatal conductance , amaranth , sorghum , transpiration , agronomy , phaseolus , eucalyptus , poaceae , amaranthaceae , botany , horticulture , photosynthesis
Measurements of CO 2 and H 2 0 exchange and the calculated leaf conductance of attached leaves in well‐watered plants were conducted over a range of leaf‐air vapor pressure differences (VPD) (1.0 to 4.0 kPa) to compare the response of cassava that of other warm‐climate species. Species tested were cassava ( Manihot esculenta Crantz), andropogon ( Andropogon gayanus Kunth), beans ( Phaseolus vulgaris L.), siratro [ Macroptilium atropurpureum (DC) urb], rice ( Oryza sativa L.), eucalyptus ( Eucalyptus deglupta Blume), amaranth weed ( Amaranthus retroflexus L.) and grain sorghum [ Sorghum bicolor (L) Moench]. Plants were grown in pots outdoors at the CIAT headquarters, Palmira, Colombia, South America. All except andropogon showed a decrease in leaf conductance with increase in VPD. The degree of stomatal sensitivity decreased as follows: cassava > siratro, amaranthus, eucalyptus, bean > sorghum, rice > andropogon. The greater sensitivity in cassava was associated with reduction in transpiration and stable leaf water potential (ψl) at large VPD. In other less sensitive species, transpiration increased and bulk leaf water potential decreased at large VPD. The response of cassava to changes in VPD resulted in higher water use efficiency (WUE = μmol CO 2 uptake per mmol H 2 O loss) compared with other C 3 species. This may contribute to the comparative advantage of cassava when grown under conditions of limited availability of water. The WUE of the C 4 species (sorghum, andropogon, amaranthus) were higher than those of the C 3 species. This greater WUE of C 4 species was attributed mainly to the higher photosynthetic rates of the C 4 species rather than to a lower transpiration rate.