Physiological aspects of sainfoin regrowth and persistence

dc.contributor.committeeChairMahan, James R.
dc.contributor.committeeMemberBritton, Carlton M.
dc.contributor.committeeMemberRichardson, C. Reed
dc.contributor.committeeMemberZartman, Richard E.
dc.creatorKallenbach, Robert L.
dc.description.abstractPoor summer regrowth and stand persistence limit sainfoin's (Onobrychls viciifolia Scop.) usefulness. The objective was to determine the effects of photoperiod, temperature, and clipping height on sainfoin growth, taproot metabolites, enzyme activity, and metabolism following defoliation. Renumex sainfoin plants clipped to 2 cm were grown in chambers under photoperiods of 10, 13, and 16 h of light d""*. Although photoperiod had some effects on sainfoin growth form (i.e., plant height and reproductive structures), the vegetative growth and metabolism of sainfoin was unaltered (p>0.05) by photoperiod. Plants were grown at air temperatures of 15, 25, or 35°C with soil temperatures of 10, 20, or 30°C. After clipping to 2 cm, plants regrew for 35 d. Increasing air temperature was negatively correlated (p<0.05) with leaves plant'1, leaf area planf"* and shoot mass plant'"* (R2's>0.75). Increasing air or soil temperature was negatively correlated (p<0.05) with crown, taproot, and fineroot mass (R2's>0.88). Increasing air temperature was positively correlated (p<0.05) with dead plants treatment""* (R2 0.90): nearly all plants died at 35°C. In the field, sainfoin plots were clipped to heights of 5, 15 or 25 cm every 35 d during the growing season. Harvested herbage mass for the 5 cm treatment was greatest, averaging 313 g m2 across harvests. Herbage mass was 170 and 241 g m2 lower (p<0.05) in the 15 and 25 cm treatments, respectively. Stands of the 5 cm treatment were only 81% of original stands in mid-July and declined to 63% by mid September. Stands in the 15 and 25 cm treatments did not change (p>0.05) throughout the study. Predicted metabolic heat rates of sainfoin increased linearly (r2 0.99) with temperature. Taproot carbohydrates did not differ among treatments, but nonreducing sugars showed seasonal fluctuations (16.5 to 100.9 g kg""*) and were lowest in summer. Sainfoin growth is limited by high metabolic rates and low taproot carbohydrates when temperatures are warm. Severe defoliation during periods of high temperatures may cause plant death because increased metabolic rates cannot be supported by existing leaf area or taproot carbohydrates.
dc.subjectSainfoin -- Growth
dc.subjectSainfoin -- Physiology
dc.titlePhysiological aspects of sainfoin regrowth and persistenceen_US
dc.typeDissertation[unknown] Tech University of Philosophy


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