Valutazione dell'efficienza d'uso dell'acqua in nuove specie ornamentali per ambienti urbani
Author(s)
Cacini, Sonia
Date Issued
March 19, 2010
Type
Doctoral Thesis
Abstract
The aim of this research was to evaluate the effects of drought and saline stress on two broadleaf hedge shrubs species, Photinia x fraseri ‘Red Robin’ and Viburnum odoratissimum, in order to assess their adaptability to these typical stress conditions of Mediterranean landscape. In a first experiment plants were grown inside a greenhouse during summer-autumn season, in pots filled with mineral soil, with different irrigation frequencies and volumes. Treatments consisted in irrigation regimes differentiated by water restitutions until container capacity (CC), when substrate
moisture reached values of 70% (control), 63% (FR) and 54% (FRR) of (CC), or when moisture of
control reached values of 70% of CC, but providing restitutions equal to 73% (VRR) and 60%
(VRR) of the control. Irrigation was managed gravimetrically. Biometric parameters and gas
exchange parameters (net photosynthesis, transpiration, stomatal conductance, internal
concentration of C02) and water use efficiency of photosynthesis were periodically monitored.
In a second experiment plants were grown inside a greenhouse during summer-autumn season, in
pots filled with peat and pumice (1:1), with different irrigation frequencies and volumes.
Treatments consisted in irrigation regimes differentiated by water restitution, when substrate moisture reached values of 66%, 73% or 80% of container capacity, or maintaining moisture constantly at 73%. Irrigation was managed automatically by FDR sensors. biometric parameters, gas exchange parameters (net photosynthesis, transpiration, stomatal conductance, internal concentration of C02), water use efficiency of photosynthesis and chlorophyll a (Chl a) fluorescence were periodically monitored.
In a third experiment plants were grown in pots filled with peat and pumice (1:1) inside a
greenhouse during summer-autumn season. Treatments consisted in four irrigation solutions
containing 0 mM, 20 mM, 40 mM and 60 mM NaCl.
Biometric parameters were periodically monitored during the experiment, together with water
relations (predawn (.PD), and midday leaf water potential (.MD), and leaf osmotic potential (.p)), gas exchange parameters (net photosynthesis, transpiration, stomatal conductance, internal concentration of C02) and Chl a fluorescence. Ions concentration of Na+, K+, Cl-and NO3 in plants was determined at the end of the trial.
In a fourth experiment plants were grown in open as hedges; treatments consisted in three irrigation regimes: hedges irrigated every 7 days, every 21 days or every 42 days. Climatic and biometric parameters and stomatal conductance were periodically monitored.
Results showed a higher adaptability of P. x fraseri ‘Red Robin’ to water stress when cultivated in pots, especially when water supply was reduced in terms of irrigation frequency. On the contrary, in open field this species showed a significant lower plant growth with the lower frequencies, even if the ornamental quality was not affected. V. odoratissimum showed tolerance to water stress when grown in pot, only after long periods of exposure. In fact, less stressed plants showed higher development with respect to the other . On the contrary, in open fields it didn’t show significant differences in growth and quality of the product.
These trials suggested that, to optimize water use and obtain high quality, it’s necessary to adapt different irrigation regimes to the different species behaviours during the cultivation in pots and after transplanting in urban condition.
In respect to salt stress experiment, P. x fraseri ‘Red Robin’ didn’t show any tolerance, with a reduction in growth, necrosis on leaf margins, strong filloptosis and reduction in .PD, .MD and .p following salt treatments. Analysis of gas exchange parameters and Chl a fluorescence didn’t show significant differences. No photodamage effects were recorded on new leaves.
Viburnum showed a great adaptability to salt stress, without phytodamage effects, but significant lower plant growth. Gas exchange parameters decreased in all treatments, while .PD, .MD and .p decreased after 90 days, but only in treatments with 40 and 60 mM NaCl. Chl a fluorescence didn’t show significant differences among treatments and no photodamage effects were registered.Concentration of Na+ and Cl-increased with increasing salinity in both species, while concentration of K+ decreased with increasing salinity; concentration of NO3 decreased with increasing salinity in P. x fraseri ‘Red Robin’, while any significant difference was observed in V. odoratissimum. The trial showed that salt stress affects strongly growth and ornamental quality of P. x fraseri ‘Red Robin’, while in V. odoratissimum also the highest concentrations of NaCl in irrigation water do not affect ornamental quality of plants.
Additional information
Dottorato di ricerca in Ortoflorofrutticoltura
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