Diurnal Variation in Root Respiration

Abstract

The existence of a diurnal fluctuation in root metabolism can be deduced from several studies. While studying root respiration, Harris (13) noted a diurnal variation in the rate of CO2 production by roots of tomatoes and certain deciduous fruit trees. Cannon (5) found oxygen consumption of roots to be increased in light under conditions conducive to high transpiration. Grossenbacher (7) (16) believes may be associated with increased transpiration during the period of illumination. Went (26) observed that the accumulation of p32 in the shoots of tomato plants was more rapid during the day.These diurnal fluctuations in root activity could be a reflection of a diurnal variation in respiration rate, as suggested by the experiments of Harris (13). However, Grossenbacher (7) were propagated in a sand bed. After 4 weeks, uniformly rooted cuttings were transplanted to culture containers patterned after the root respiration apparatus described by White and Childers (27). Culture containers were 19-liter glass bottles with a 2.5 cm diameter hole drilled in the bottom. The bottles were inverted, filled with pea-sized gravel and the plant inserted through the hole. The woody stem of this species allowed the culture vessel to be completely sealed except for inlet and outlet tubes. Nutrient solution (Shive's R5C,, complete with iron and micronutrients) (21) was supplied by sub-irrigation. The containers were immersed in separate water baths which were controlled by individual thermostats to provide 15.6, 21.1, 26.7, and 32.2 C temperatures about the root systems. The shoots, however, were exposed to the normal greenhouse environment.Since the primary purpose of the Derris experiment was to study the long-term effect of root temperature on the synthesis of rotenone, the respiration studies were made just prior to harvest when the plants were 28 months old.Respiration measurements were made by periodically displacing the total volume of air from the gravel-filled bottles with nutrient solution. Aliquots of the displaced gas mixture were assayed for CO2 and 02 content by the procedure of Haldane (10). Measurements were made on duplicate plants for each of the four temperature treatments. Air samples were taken at 6-hour intervals, beginning at 6 AM for 5 days. Air volume was corrected to standard temperature and pressure.-

The Effect of Photoperiod Duration Upon the Respiratory Activity of the Roots of Wheat Seedlings

“…Consequently it might be expected that the normal diurnal cycle of light and dark would affect root growth rates and root metabolism. Head (1965) has demonstrated a diurnal fluctuationt in the growth rate of the roots of cherry trees growing naturally in soil; and Huck, Hageman, and Hanson (1962) examined the respiratory activity of the roots of three species of plant growing in sand and nutrient culture solution and concluded that diurnal fluctuations in root respiration rate did occur.…”

“…However, with one exception, the experiments of Huck, Hageman, and Hanson (1962) were not done in a controlled environment, and root temperatures differed by 5 degC from day to night. Also the contribution of microorganism respiration in the root containers was not estimated, although the plants in one experiment were in the same container for 28 months.…”

“…roots of wheat seedlings held under controlled conditions. The periodic gas-sampling technique that Huck, Hageman, and Hanson (1962) used in the measurement of root respiration rates was replaced by a continuous gas-sampling method, in which a CO 2 infrared gas analyser was used.…”

“…The consistency of timing of these peaks and troughs in root respiration rate is indicated by their small standard error (Table 2). Huck, Hageman, and Hanson (1962), who made no measurements of the effects of the respiratory activity of microorganisms in the rooting medium and who used a greenhouse environment without controlled temperatures in all except one of their experiments, also concluded that light-controlled fluctuations in root respiration rate occurred in Derris elliptica (Wall), Zea mays (L.), and Glycine max (L.). However, they give only one plot of root respiration rates, continuously recorded, and this was for plants growing in a greenhouse under natural photoperiods, when in two out of the three 24-hr cycles followed, there was only a single peak in the root respiration rate.…”

Carbohydrate Partitioning and the Capacity of Apparent Nitrogen Fixation of Soybean Plants Grown Outdoors

“…These results are similar to a controlled-environment study (29) but differ from the results of Huck et al (1 1) where dirunal changes in root respiration occurred despite controlled root-zone temperature. Huck et al ( 11) and others (20,23) have suggested that the acetylene reduction and respiratory activity of nodules also responds to shoot temperature, perhaps resulting from temperature effects on vein loading and carbohydrate translocation from the shoot to nodules. Vein loading and translocation in the phloem ofwheat plants, however, is largely unaffected by temperatures from 20 to 40C (26).…”