Escape from water or remain quiescent? Lotus tenuis changes its strategy depending on depth of submergence.
OBJECTIVE
Two main strategies that allow plants to cope with soil waterlogging or deeper submergence are: (1) escaping by means of upward shoot elongation or (2) remaining quiescent underwater. This study investigates these strategies in Lotus tenuis, a forage legume of increasing importance in areas prone to soil waterlogging, shallow submergence or complete submergence.


METHODS
Plants of L. tenuis were subjected for 30 d to well-drained (control), waterlogged (water-saturated soil), partially submerged (6 cm water depth) and completely submerged conditions. Plant responses assessed were tissue porosity, shoot number and length, biomass and utilization of water-soluble carbohydrates (WSCs) and starch in the crown.


RESULTS
Lotus tenuis adjusted its strategy depending on the depth of submergence. Root growth of partially submerged plants ceased and carbon allocation prioritized shoot lengthening (32 cm vs. 24.5 cm under other treatments), without depleting carbohydrate reserves to sustain the faster growth. These plants also developed more shoot and root porosity. In contrast, completely submerged plants became quiescent, with no associated biomass accumulation, new shoot production or shoot elongation. In addition, tissue porosity was not enhanced. The survival of completely submerged plants is attributed to consumption of WSCs and starch reserves from crowns (concentrations 50-75 % less than in other treatments).


CONCLUSIONS
The forage legume L. tenuis has the flexibility either to escape from partial submergence by elongating its shoot more vigorously to avoid becoming totally submerged or to adopt a non-elongating quiescent strategy when completely immersed that is based on utilizing stored reserves. The possession of these alternative survival strategies helps to explain the success of L. tenuis in environments subjected to unpredictable flooding depths.
Manzur
M E
ME
IFEVA-CONICET, Facultad de Agronomía, Universidad de Buenos Aires, Avenida San Martín 4453, CPA 1417 DSE Buenos Aires, Argentina. mmanzur@ifeva.edu.ar
Grimoldi
A A
AA
Insausti
P
P
Striker
G G
GG
D000388:Air; D018533:Biomass; D002241:Carbohydrates / Q000032:analysis; D055868:Floods; D000070116:Lotus / Q000502:physiology*; D009928:Organ Specificity; D018515:Plant Leaves / Q000502:physiology; D018517:Plant Roots / Q000502:physiology; D018520:Plant Shoots / Q000033:anatomy & histology; D016062:Porosity; D012987:Soil; D012995:Solubility; D014867:Water / Q000502:physiology*
D002241:Carbohydrates; D012987:Soil; D014867:Water
Ann Bot. 2005 Sep;96(4):581-9
16024559
Ann Bot. 2003 Jan;91 Spec No:227-41
12509343
Ann Bot. 2008 Jan;101(2):229-48
17956854
Trends Plant Sci. 2004 Sep;9(9):449-56
15337495
Ann Bot. 2009 Jan;103(2):359-76
19001429
Plant Physiol. 1990 Nov;94(3):1071-7
16667798
J Exp Bot. 2001 Nov;52(364):2213-25
11604461
Ann Bot. 2003 Jan;91(1):75-84
12495922
Funct Plant Biol. 2003 Aug;30(7):813-819
32689065
Planta. 1992 Nov;188(4):611-8
24178396
Annu Rev Plant Biol. 2008;59:313-39
18444902
Plant Cell Physiol. 2006 Jan;47(1):128-40
16284407
Ann Bot. 2008 Aug;102(2):247-54
18499769
New Phytol. 2008;177(4):918-926
18086222
Plant Physiol. 1983 Jun;72(2):441-6
16663022
New Phytol. 2006;170(2):213-26
16608449
Biochem J. 1954 Jul;57(3):508-14
13181867