Waterlogging effects on physiological and growth responses in forage grasses with differential tolerance

PLOSCHUK, EL; GRIMOLDI, AA; PLOSCHUK, RA; STRIKER, GG

Elsinore

Congreso; 12th Conference International Society for Plant Anaerobiosis; 2016

ISPA. International Association of Plant Anaerobiosis

Waterlogging tolerance differs among forage species. The grasses Dactylis glomerata and Bromus unioloides are regarded as relatively sensitive to soil oxygen deficiency while Festuca arundinacea and Phalaris aquatica are considered tolerant. So far, these reputations are mostly based on dry mass responses at the end of a waterlogging period. However, the physiological performance associated with differential responses among species and the ability to recover from waterlogging after water subsides have not been addressed. To expand our knowledge, during 15 days, 42-day-old plants of these species growing in 0.6L pots with top soil of a natural grassland (3.3% organic carbon) and sand (1:1 v/v) were subjected to: (i) well drained conditions (i.e. field capacity) and (ii) waterlogging (1-2 cm water above soil). After the waterlogging period, plants were allowed to grow for 15 days in well drained conditions to assess the recovery degree. Plant physiological responses, including net photosynthesis, stomatal conductance and transpiration rate of fully expanded leaves of similar age/position were measured at the beginning of the experiment (day 0), and at 2, 7 and 15 days of waterlogging. Plant morphology was characterized by examining the number of tillers per plant and green leaves per tiller at days 0, 5, 12 (during waterlogging), 19 and 26 days (during recovery). Dry mass accumulation was assessed by harvesting plants at the beginning of experiment (day 0) and at the end of waterlogging (day 15) and recovery (day 30) periods. Results showed that, under waterlogging conditions, the species D. glomerata and B. unioloides showed progressive reductions in net photosynthesis (20-36% respectively) and stomatal conductance (29-32%, respectively) compared with their controls (P0.3). Along the experiment, the number of tillers per plant was not affected by waterlogging in any of these grasses (P>0.6), while the number of green leaves per tiller was reduced (23%; P=0.03) by the end of waterlogging only in the sensitive species D. glomerata. Plant dry mass accumulation during the waterlogging period was slightly reduced (22-11%; marginally significant with P=0.1) in D. glomerata, B. unioloides and F. arundinacea, mainly due to root growth arrestment, and it was increased by 39% in the waterlogging tolerant P. aquatic (P