Long-term drought stress alters nitrogenase activity and carbon translocation in split-root cultured Alnus incana

Abstract

K. 1995. Long-term drought stress alters nitrogenase activity and carbon translocation in split-root cultured Alnus incana. -Physiol. Plant. 94: 181-186.Split-root cultured grey alder, Ainus incana (L.) Moench., was grown in sand in cuvettes with a continuous supply of nutrient solution. During the drought treatment for up to 9 days the supply of solution was withheld from one of the split-root halves. After 2-3 days of treatment, soil water became depleted and the unwatered root halves were at a constant drought stress, water potential (W,^ui,J = -1.1 to -1.6 MPa. Nitrogenase activity in the drv' half decreased to about 70% of the initial value during the first 2-3 days and then stayed al this level. The water supply to the shoot from the wet root half was high and only a temporary slight decrease in photosynthesis and stomata! conductance was found in drought-stressed split-root plants. Labelling studies showed a reduced translocation of phoioassimilates to the dry nodules. The fixation of CO, in the nodules seemed to be more tolerant to drought than nitrogenase activity. During the drought treatment there was an osmotic adjustment from -0.9 to -1.7 MPa. but no change in the storage of starch in tbe nodules. In alders where parts of the root system is kept dry these roots acclimate and continue a persistent nitrogenase activity.

Actinorhizal symbioses and their N2 fixation

“…In the split-root system, ARA decreased rapidly after 2-3 d when the roots had drained the surrounding sand, and then ARA stayed at this level for at least 1 wk. The watered root half had to supply the dry half with water via the shoot, and neither photosynthesis nor stomatal conductance were affected (Sundstrom & Huss-Danell, 1995). The decreased but stable ARA in nodules on the dry half was in agreement with a low but stable supply of^C from the shoot, whereas ^*CO2 fixation in the nodules seemed unaffected by the drought treatment (Sundstrom & Huss-Danell, 1995).…”

“…The watered root half had to supply the dry half with water via the shoot, and neither photosynthesis nor stomatal conductance were affected (Sundstrom & Huss-Danell, 1995). The decreased but stable ARA in nodules on the dry half was in agreement with a low but stable supply of^C from the shoot, whereas ^*CO2 fixation in the nodules seemed unaffected by the drought treatment (Sundstrom & Huss-Danell, 1995). In the field, it is often observed that some roots on a plant experience drought whereas others do not.…”

“…W^hen alders were acclimated to drought, nitrogenase activity was not significantly affected at this water potential (Hennessey et al, 1989;Seiler & Johnson, 1984). More detailed information was obtained from experiments in which different parts of a root system were subjected to different degrees of drought, either by keeping the upper part of the root system dry and the lower part watered (Harrington & Seiler, 1988) or by using a split-root system (Sundstrom & Huss-Danell, 1995). In the horizontally divided system, no significant effect on ARA and transpiration was found in the stressed nodules.…”

Volatile organic compound emissions from Alnus glutinosa under interacting drought and herbivory stresses

“…altering their survival, growth and even reproduction, thereby influencing the composition of early successional alder dominated ecosystems. So far, only a few studies have investigated stress induced by herbivore attack (e.g., Blande et al 2010; Dolch and Tscharntke 2000; Giertych et al 2006; Tscharntke et al 2001) or by drought (Arbellay et al 2010; Francis et al 2005; Hacke and Sauter 1996; Sundstrom and Hussdanell 1995) in Alnus spp, but the combined stress has not been studied in alder to our knowledge.…”