|Shields Jr, Fletcher|
Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2005
Publication Date: 3/28/2006
Citation: Li, S., Pezeshki, S.R., Shields, F.D., Jr. 2006. Partial flooding enhances aeration in adventitious roots of black willow (Salix nigra) cuttings. Journal of Plant Physiology 163(12):619-628.
Interpretive Summary: Planting cuttings from willow trees is an effective and economical approach for re-establishing woody vegetation within eroding channels. However, willow plantings often fail to survive in extremely wet soils, which frequently occur at the bank toe where erosion protection is badly needed. A laboratory study was conducted to measure the effects of soil flooding on two adaptations that willow exhibit to flooded conditions: the formation of aerenchyma, or porous root tissue that serves as a conduit for air from the surface to the root zone, and the rate of movement of oxygen from roots into the surrounding soil. Two situations were compared to a well-drained control: the soil was flooded completely, with water standing above the soil surface, and soil was flooded only up to 10 cm below the surface. The partially flooded plants developed more aerenchyma and pumped more oxygen into the soil around their roots than either the control plants or the completely flooded plants. These results will guide future research on pre-planting treatments for willow cuttings and reinforce earlier empirical findings about the unsuitability of willow cuttings for stabilizing extremely wet sites.
Technical Abstract: Black willow (Salix nigra) cuttings are widely used for streambank stabilization. Flooding has been shown to adversely impact cutting performance, and improved understanding of natural adaptations to flooding might suggest handling and planting techniques to enhance success. This experiment was designed to examine the effects of continuous and partial flooding of young willows grown from cuttings on aerenchyma formation and radial oxygen loss. Photosynthetic and growth responses to these conditions were also investigated. Under laboratory conditions, replicated potted cuttings were subjected to three treatments: no flooding (control, C), continuous flooding (CF) and partial flooding (PF). Water was maintained above the soil surface in CF and at 10 cm below the soil surface in PF. Results indicated that after the 28-day treatments, root porosity ranged between 28.6% and 33.0% for the CF and C plants but was greater for the PF plants (39.2% for the drained and 37.2% for the flooded portions). A similar response pattern was found for radial oxygen loss. Neither CF nor PF treatments had any detectable adverse effects on plant gas exchange or photosystem II functioning. S. nigra cuttings exhibited avoidance mechanisms in response to flooding, especially the partially flooded condition which is common in riparian habitats.