Pattern of Respiration of a Perennial Ryegrass Crop in the Field |
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Authors: | JONES M B; LEAFE E L; STILES W; COLLETT B |
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Institution: | The Grassland Research Institute Hurley, Maidenhead, Berkshire, SL6 5LR |
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Abstract: | Dark respiratory losses of CO2 were measured ona one year old sward of S24 perennial ryegrass (Lolium perenneL.) at intervals during a 74 day reproductive growth period,between April and June, and a 21 day vegetative growth period,in July and August. Part of the sward was shaded for one weekbefore measure ments commenced. Measurements of darkrespiration continued for 46 hand it was possible to distinguishtwo components which are designated maintenanceand synthetic Maintenance respiration was taken to be the meanrate of CO2 efflux after 4046 h darkness. When calculatedon a plant d. wt basis at 15°C it ranged between 6 to 32mgCO2 g-1 day-1 during reproductive growth and 1014 mgCO2 g-1 day-1 during vegetative growth. During reproductivegrowth, sward protein content ranged between 723 percent and when maintenance respiration was recalculated on thebasis of protein content it changed relatively little throughoutthe growth period (90140 mg CO2 g pro tein-1 day-1);the value for vegetative growth ranged between 70100mgCO2 g protein-day-1. Total synthetic CO2 flux was determined duringreproductive growth and a rate of synthetic CO2flux was determined during both reproductive and vegetativegrowth. Between 15 and 35 per cent of the CO2 fixed in the previousphotoperiod was lost in synthetic respirationof above-ground material in reproductive swards. Previous shadingincreased the proportion of synthetic CO2 lossfrom above ground. The rate of synthetic CO2 outputduring the first hours of darkness increased with amount ofCO2 fixed in the previous photoperiod, although it was not proportionalto it. There is some evidence that assimilate is carried-overfrom one photoperiod to the next. |
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