Stimulation of the ionic transport system in Brassica napus by a plant growth-promoting rhizobacterium (Achromobacter sp.).
A plant growth-promoting rhizobacterium belonging to the genus Achromobacter was isolated from the oil-seed-rape (Brassica napus) root. Growth promotion bioassays were performed with oilseed rape seedlings in a growth chamber in test tubes containing attapulgite and mineral nutrient solution, containing NO3- as N source. The presence of this Achromobacter strain increased shoot and root dry weight by 22-33% and 6-21%, respectively. Inoculation of young seedlings with the Achromobacter bacteria induced a 100% improvement in NO3- uptake by the whole root system. Observations on the seminal root of seedlings 20 h after inoculation showed that there was an enhancement of both the number and the length of root hairs, compared to non-inoculated seedlings. Electrophysiological measurements of NO3- net flux with ion-selective microelectrodes showed that inoculation resulted in a specific increase of net nitrate flux in a root zone morphologically similar in inoculated and non-inoculated plants. The root area increased due to root hair stimulation by the Achromobacter bacteria, which might have contributed to the improvement of NO3- uptake by the whole root system, together with the enhancement of specific NO3- uptake rate. Moreover, inoculated plants showed increased potassium net influx and proton net efflux. Overall, the data presented suggest that the inoculation of oilseed-rape with the bacteria Achromobacter affects the mineral uptake.
Bertrand
H
H
Laboratoire des Symbioses Tropicales et Méditerranéennes, Laboratoire commun ORSTOM/ CIRAD-Forêt /INRA /ENSA-M, Montpellier, France.
Plassard
C
C
Pinochet
X
X
Touraine
B
B
Normand
P
P
Cleyet-Marel
J C
JC
D000421:Alcaligenes / Q000502:physiology*; D001937:Brassica / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology*; D004275:DNA, Ribosomal / Q000032:analysis / Q000235:genetics; D004594:Electrophysiology; D020459:Genes, rRNA; D017136:Ion Transport; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D011522:Protons; D012336:RNA, Ribosomal, 16S / Q000235:genetics
D004275:DNA, Ribosomal; D009566:Nitrates; D011522:Protons; D012336:RNA, Ribosomal, 16S; D011188:Potassium