Tolerance to partial and complete submergence in the forage legume Melilotus siculus: an evaluation of fifteen accessions for petiole hyponastic response and gas-filled spaces, leaf hydrophobicity and gas films, and root phellem

COLMER TD; STRIKER GG; KOTULA L

ANNALS OF BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2019 vol. 123 p. 169 - 180

0305-7364

Background and Aims Submergence is a severe stress for most plants. Melilotus siculus is a waterlogging (i.e. root-zone hypoxia) tolerant annual forage legume, but data were lacking for the effects of partial and full submergence of the shoots. The aim was to compare the tolerance to partial and full submergence of fifteen M. siculus accessions and to assess variation in traits possibly contributing to tolerance. Recovery ability post-submergence was also evaluated. Methods A factorial experiment imposed treatments of water level (aerated root-zone with shoots in air - controls, stagnant root-zone with shoots in air, stagnant root-zone with partial (75%) or full shoot submergence) on fifteen accessions, for 7 days on 4-week-old plants in a 20/15oC day/night phytotron. Measurements included: shoot and root growth, hyponastic-petiole responses, petiole gas-filled spaces, leaflet sugars, leaflet surface hydrophobicity, leaflet gas film thickness, and phellem area near the base of the main root. Recovery following full submergence was also assessed.Key Results Accessions differed in shoot and root growth during partial and full shoot submergence. Traits differing among accessions and associated with tolerance were leaflet gas film thickness upon submergence, gas-filled spaces in petioles and phellem tissue area near the base of the main root. All accessions were able to re-orientate petioles towards the vertical both under partial and full submergence. Petiole extension rates were maintained during partial submergence, but decreased during full submergence. Leaflet sugars accumulated during partial submergence, but were depleted during full submergence. Growth resumption after full submergence differed among accessions and was positively correlated with the number of green leaves retained at desubmergence. Conclusions Melilotus siculus is able to tolerate partial and full submergence of at least seven days. Leaflet surface hydrophobicity and associated gas film retention, petiole gas-filled porosity and root phellem abundance are important traits contributing to tolerance. Post-submergence recovery growth differs among accessions. The ability to retain green leaves is essential to succeed during recovery.