Search

Elongation-induced leaf emergence is one wayfor plants to deal with complete submergence by 'escaping' from water. This growth strategy is hypothesised to be more beneficial under single long-term submergence than under repeated short-term submergence events (i.e.fluctuating environment), as costs of repeated plant 'adjustment' would exceed the initial benefits of shoot elongation. To test this idea, 2-week-old plants of Chloris gayana Kunth. cv. Fine Cut (a submergencetolerant cultivar first selected by a screening experiment) were grown for 4 weeks under (i) control conditions, (ii) two 1-week submergence cycles, or (iii) one 2-week submergence cycle. Additionally, a set of plants were placed below nettings to assess the cost of remaining forcedly submerged. Impeding leaves emergence through nettings did not compromise survival when submergence was 1-week long, but determined the death of all plants when extended to 2 weeks. Growth as affected by flooding regime revealed that under one 2-week submergence event, plants accumulated a 2.9-fold higher dry mass than when they experienced the same submergence duration in separate events along 1week. The 'escape' strategy in the grass C. gayana, by which leaf contact with air is re-established, is essential for its survival, and it is more beneficial for plant growth under long-term submergence than under repeated short-term submergence cycles. [ABSTRACT FROM AUTHOR]

Three plant communities positioned along a subtle topographic gradient, referred to as upland, intermediate, and lowland positions, characterize the landscape of the Flooding Pampa grasslands of Argentina. Although it is believed that the structure and functioning of the plant communities at each position are in close relationship with their hydric regime, this has never been quantified. More than 800 measurements of soil water content during four years, along with soil water retention curves, and physical and chemical parameters of soils were assessed at each position. Results showed that water availability during the year varied among the positions in accordance with differences in hydrological balance and soil water retention capacity of each of them. Water retention increased in relation to clay and organic matter content from the upland to the lowland position. The upland position, with more soil sand content, registered severe drought events during late spring and summer, without flooding periods in any season. The intermediate and lowland positions, with more soil clay content, remained flooded for several weeks during winter and spring, and they manifested less severe summer droughts than the upland position. Moreover, the lowland position was more hydromorphic than the intermediate one. These spatial and temporal variations of water regime and soil parameters characterizing the upland, intermediate, and lowland positions concur with different plant communities associated with each of them. [ABSTRACT FROM AUTHOR]

Highlights: [•] Spartina densiflora dominates along topographical gradients of salt marshes. [•] Responses of upland and lowland plants to tidal flooding were assessed. [•] Lowland plants performed better in leaf length, ion regulation, and leaf span. [•] Acclimation of characters of S. densiflora plants to their habitat were found. [ABSTRACT FROM AUTHOR]