Effect of water salinity and osmolytes application on growth and ornamental value of Viburnum lucidum L.

The scarcity of good quality water frequently led to the use of saline water for the irrigation of ornamental shrubs. Therefore, their salt tolerance needs to be investigated, along with the possibility to counteract the effect of salinity exposure on plant growth and ornamental quality, possibly due to reduced growth, and nutritional imbalances. Under salt stress conditions, plants can activate mechanisms helping to withstand it, such as the production of several organic solutes that play a role in the osmotic adjustment. Aiming to this extent the exogenous application of osmolytes, such as glycine betaine (GB) and L-proline (L-P), has been tested on potted plants of Viburnum lucidum L. grown under saline irrigation. The experiment was designed as a factorial combination of two nutrient solutions (non-salt control, or 200 mM NaCl) and three osmoprotectant treatments (untreated, GB 2.5 mM, or L-P 5 mM application). Shoot and root biomass were negatively affected by salinity (-37 and 
-29%, respectively), but not the shoot/root ratio. A significant and positive effect of osmolytes application was found on the shoot biomass of plants treated with GB (+46%). Lateral sprouting total length per plant was also reduced by saline irrigation (-60%), but the GB application resulted in a significant increase (+102%). A positive effect of GB application was also found on the total leaf area (LA) per plant that was increased by 182% under saline conditions. Root/shoot ratio did not change with salinity. L-P application resulted in a significant increase of both shoot and root biomass per unit of LA (+40 and +85%, respectively) in comparison with the untreated control and GB.