1. Impact of high or low levels of phosphorus and high sodium in soils on productivity and stress tolerance of Arundo donax plantsClaudia Cocozza, Federico Brilli, Laura Miozzi, Sara Pignattelli, Silvia Rotunno, Cecilia Brunetti, Cristiana Giordano, Susanna Pollastri, Mauro Centritto, Gian Paolo Accotto, Roberto Tognetti, Francesco Loreto, 2019, original scientific article Abstract: The potential of Arundo donax to grow in degraded soils, characterized by excess of salinity (Na+), and phosphorus
deficiency (-P) or excess (+P) also coupled with salinity (+NaP), was investigated by combining in vivo
plant phenotyping, quantification of metabolites and ultrastructural imaging of leaves with a transcriptome-wide
screening. Photosynthesis and growth were impaired by+Na, -P and+NaP. While+Na caused stomatal
closure, enhanced biosynthesis of carotenoids, sucrose and isoprene and impaired anatomy of cell walls, +P
negatively affected starch production and isoprene emission, and damaged chloroplasts. Finally, +NaP largely
inhibited photosynthesis due to stomatal limitations, increased sugar content, induced/repressed a number of
genes 10 time higher with respect to+P and+Na, and caused appearance of numerous and large plastoglobules
and starch granules in chloroplasts. Our results show that A. donax is sensitive to unbalances of soil ion
content, despite activation of defensive mechanisms that enhance plant resilience, growth and biomass production
of A. donax under these conditions. Keywords: Abiotic stress
Giant reed
Isoprene emission
Phosphorus
Salinity
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2. The excess of phosphorus in soil reduces physiological performances over time but enhances prompt recovery of salt-stressed Arundo donax plantsClaudia Cocozza, Federico Brilli, Sara Pignattelli, Susanna Pollastri, Cecilia Brunetti, Cristina Gonnelli, Roberto Tognetti, Mauro Centritto, Francesco Loreto, 2020, original scientific article Abstract: Arundo donax L. is an invasive grass species with high tolerance to a wide range of environmental stresses. The
response of potted A. donax plants to soil stress characterized by prolonged exposure (43 days) to salinity (+Na),
to high concentration of phosphorus (+P), and to the combination of high Na and P (+NaP) followed by 14 days
of recovery under optimal nutrient solution, was investigated along the entire time-course of the experiment.
After an exposure of 43 days, salinity induced a progressive decline in stomatal conductance that hampered A.
donax growth through diffusional limitations to photosynthesis and, when combined with high P, reduced the
electron transport rate. Isoprene emission from A. donax leaves was stimulated as Na+ concentration raised in
leaves. Prolonged growth in P-enriched substrate did not significantly affect A. donax performance, but decreased
isoprene emission from leaves. Prolonged exposure of A. donax to + NaP increased the leaf level of
H2O2, stimulated the production of carbohydrates, phenylpropanoids, zeaxanthin and increased the de-epoxidation
state of the xanthophylls. This might have resulted in a higher stress tolerance that allowed a fast and full
recovery following stress relief. Moreover, the high amount of ABA-glucose ester accumulated in leaves of A.
donax exposed to + NaP might have favored stomata re-opening further sustaining the observed prompt recovery
of photosynthesis. Therefore, prolonged exposure to high P exacerbated the negative effects of salt stress
in A. donax plants photosynthetic performances, but enhanced activation of physiological mechanisms that allowed
a prompt and full recovery after stress. Keywords: Arundo donax
Phosphorus
Salinity
Stress tolerance
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