Premium
Physiological Ecology of Three Codominant Successional Annuals
Author(s) -
Wieland N. K.,
Bazzaz F. A.
Publication year - 1975
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1935502
Subject(s) - abutilon , photosynthesis , biology , setaria viridis , setaria , botany , ecology , agronomy , weed
Setaria faberii, Abutilon theophrastii, and Polygonum pensylvanicum growing together in a 1—yr successional field exhibit differing daily patterns of leaf water potential; S. faberii develops and maintains more negative water potentials than A. theophrasti, and P. pensylvanicum maintains much less negative water potential than either species. Setaria faberii and P. pensylvanicum do not light—saturate at 1.1 x 10 5 lx irradiance while A. theophrasti approaches light saturation at 8 x 10 4 lx, indicating that the species are adapted to high light intensities of the open field. In the field, leaf temperatures are maintained appreciably below air temperatures and are in the range of temperatures consistent with near—maximal photosynthetic rates. Under optimal conditions the rates of photosynthesis are 38, 24, and 18 mg CO 2 °dm — 2 °h — 2 respectively for S. faberii, A. theophrasti, and P. pensylvanicum. Setaria faberii maintains near—maximum photosynthesis down to water potential of —12 bars, photosynthesizes at 30% of maximum at —24 bars, and recovers from potentials of —50 bars. In A. theophrasti photosynthesis remains unchanged to —10 bars, and becomes negligible at °—26 bars. In P. pensylvanicum photosynthesis begins to decline sharply at potentials of —6 bars; it becomes negligible at —18 bars; and the plants die at —20 bars. The root systems of the three species grow in different parts of the soil resource; the root system of S. faberii is fibrous and shallow; the tap root of A. theophrasti is sparsely branched and extends to intermediate depths; the tap root system of P. pensylvanicum is moderately branched in the upper soil layers and proliferates mostly below the rooting zone of the other two species. The three species have evolved differing intercompenstory mechanisms for habitat exploitation. One apparent niche difference among the species that allows for their coexistence is the exploitation of various levels of the soil and consequently different moisture resources.