Abstract
We describe the responses of Impatiens walleriana to polyethylene glycol (PEG)-induced physiological drought and the potential of exogenous salicylic acid (SA) as stress-ameliorating agent. Impatiens shoot culture was established on 16 different media containing 0–3% PEG and 0–3mM SA. After prolonged drought (60days), water relation parameters, oxidative stress indicators, and growth responses of the shoots to PEG and/or SA were recorded. PEG reduced growth, fresh weight, the number of developed leaves and shoots (proliferation rate, PR), relative water content, and chlorophyll content. PEG increased leaf water loss (LWL) and caused accumulation of proline, H2O2, and malondialdehyde. The activities of catalase, superoxide dismutase, and peroxidase were increased in response to PEG in a dose-dependent manner, with specific peroxidase isoforms induced by drought. Exogenous SA counteracted the effects of PEG on growth, physiological and biochemical parameters, except on proline accumulation. SA was particularly effective in enhancing PR, preserving LWL, and protecting photosynthetic pigments and membranes from oxidative damage. Proline accumulation was strongly enhanced by both PEG and SA. SA had differential effects on different peroxidase isoforms. SA may be safely used in 2–3mM concentration for drought protection of Impatiens with no negative effects.
Highlights
Genus Impatiens (Balsamiaceae) includes over 900 species of annual or perennial herbs (Grey-Wilson, 1980)
Plants grown on 3% polyethylene glycol (PEG) were smaller in comparison to the control plants, whereas 3 mM salicylic acid (SA) had no apparent effects on growth of the unstressed plants (Fig. 1)
When exposed to 3% PEG, plants were 50.2% shorter, had 54.0% less leaves, 85.7% lower Proliferation rate (PR), and their Fresh weight (FW) was reduced to 61.1% that of control (Fig. 2)
Summary
Genus Impatiens (Balsamiaceae) includes over 900 species of annual or perennial herbs (Grey-Wilson, 1980). Due to their beauty and long flowering period, many Impatiens species are cultivated worldwide as bedding or potted plants. I. walleriana is the most popular among the Impatiens species, having fleshy, succulent leaves and a variety of flower colors. Prolonged water deficit in potted I. walleriana plants reduced height, shoot number, dry weight, and flower number (Blanusa, 2009), while osmotic stress in hydroponically grown I. walleriana reduced height and width of the plantlets, as well as their root length. Physiological and biochemical responses to water stress in Impatiens have not been studied
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