Starch-Based Superabsorbent Enhances the Growth and Physiological Traits of Ornamental Shrubs

Periods of heat and water deficit often occur together and are especially dangerous for plants grown in pots, where the substrate volume for roots is limited. The purpose of the present research was to understand the response of shrubs planted in containers to the addition of a starch-based superabsorbent to their growing medium. The growth parameters, physiological conditions, and oxidative stress of Cornus alba ’Aurea’, Hydrangea paniculata ‘Limelight’, and Physocarpus opulifolius ‘Red Baron’ were assessed by adding a hydrogel (1, 2, or 3 g·dm −3 ) to their growing medium. The use of the superabsorbent improved the stomatal conductance and photosynthetic rate, resulting in better growth parameters. The application of 1 g·dm −3 hydrogel increased the chlorophyll content in hydrangea and ninebark leaves (8%) and increased the content of total soluble sugars in these plants (12% and 15%, respectively). The highest increase in reducing sugars was caused by a dosage of 3 g·dm −3 . The lowest dose of hydrogel resulted in a decrease in hydrogen peroxide content in the leaves of all the taxa. The relationship between the contents of biologically active components and oxidative stress proved ambiguous for all the taxa. Oxidative stress was reduced, as evidenced by lower hydrogen peroxide and an increase in pigment content. In summary, a hydrogel dosage of 2 g·dm −3 in the medium could be optimal in pot nursery production using 3 dm 3 pots.