Abstract
Promotion of nonfood species production to marginal, degraded lands abandoned by mainstream agriculture is affected by extremes of water availability (droughts and floods), which have increased in frequency and intensity and account for severe yield reduction. Arundo donax L., known as giant cane or giant reed, spontaneously grows in different kinds of environments with limitation to low temperature and is thus widespread in temperate and hot areas around the world. Moreover, this perennial rhizomatous grass has been recognized as a leading candidate crop in the Mediterranean for lignocellulosic feedstock due to its high C3 photosynthetic capacity, positive energy balance and low agroecological management demand. In this study, the photosynthetic performance and growth response of A. donax to waterlogging and submergence stress following a time course as well as their respective re-oxygenation were analyzed under reproducible and controlled environment conditions. Results of growth response showed that biomass production was strongly conditioned by the availability of oxygen. In fact, only waterlogged plants showed similar growth capacity to those under control conditions, while plants under submergence resulted in a dramatic reduction of this trait. The simultaneous measurements of both gas exchanges and chlorophyll fluorescence highlighted an alteration of both stomatal and non-stomatal photosynthetic behaviors during a short/medium period of oxygen deprivation and re-oxygenation. Photosynthetic CO2 uptake was strictly related to a combination of stomatal and mesophyll diffusional constrains, depending on the severity of the treatment and exposure time. Conditions of waterlogging and hypoxia revealed a slight growth plasticity of the species in response to prolonged stress conditions, followed by a fast recovery upon reoxygenation. Moreover, the rapid restoration of physiological functions after O2 deprivation testifies to the environmental plasticity of this species, although prolonged O2 shortage proved detrimental to A. donax by hampering growth and photosynthetic CO2 uptake.
Highlights
The use of marginal lands has gained attention as a sustainable strategy for bioenergy decreasing conflicts within food and fuel, and negative environmental impacts due to indirect land-use change (Gopalakrishnan et al, 2011)
Giant reed exhibited increasing susceptibility in terms of above-ground fresh weight (FW) as exposure time was prolonged, the differences were less pronounced for prolonged exposure times, and no significant differences were detected among the two low O2 treatments (Figure 1)
At 4 days of treatment (DOT), waterlogged plants exhibited rapid regrowth and gradually increased above-ground FW starting from 1 day of recovery
Summary
The use of marginal lands has gained attention as a sustainable strategy for bioenergy decreasing conflicts within food and fuel, and negative environmental impacts due to indirect land-use change (Gopalakrishnan et al, 2011) To accomplish this goal, it is essential to develop and adopt germplasms that are better able to tolerate abiotic threats, selecting non-food species based on their performance under less than favorable conditions. Hypoxia has recently shown to be a relevant environmental component, globally impacting on plant biodiversity and crop production (Pucciariello and Perata, 2017). Events such as strong and frequent precipitation, poor soil quality, slow drainage after over-irrigation, or winter ice encasement limit the oxygen (O2) in plants. Some grass species grown in waterlogged soils or poorly drained areas are susceptible to pests such as Pythium spp., Colletotrichum graminicola (Ces.) Wils., or Gaeumannomyces graminis var. graminis, which can develop perfectly under these environmental conditions (Pompeiano et al, 2017a)
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