Submergence tolerance in Melilotus siculus accessions concerning variation in petiole hyponastic response and gas-filled spaces, leaf hydrophobicity and root phellem

COLMER TD; KOTULA L; STRIKER GG

Taipei

Conferencia; 13th International Society for Plant Anaerobiosis Conference; 2019

Submergence is a severe stress for most plants. Melilotus siculus is a waterlogging tolerant annual legume, but data were lacking for the effects of partial and full submergence of shoots. The aim was to compare the tolerance to partial and full submergence of fifteen M. siculus accessions and to assess variation in traits contributing to tolerance. 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 main root. Recovery following full submergence was assessed. The 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, gasfilled spaces in petioles and phellem tissue area near the base of main root. All accessions were able to reorientate 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. We conclude that M. siculus can tolerate partial and full submergence of at least 7 days, and that accessions differ in tolerance. Leaflet surface hydrophobicity and associated gas film retention, petiole gas-filled porosity and root  phellem abundance are traits contributing to tolerance. Post-submergence recovery growth differs among accessions and the ability to retain green leaves is essential to succeed during recovery.