Differential responses of oat cultivars to phosphatase deprivation: plant growth and acid phosphatase activities

The effect of phosphate starvation on growth and acid phosphatases (APases) localization and activity in oat tissues was investigated. Oat cultivars (Avena sativa L.— Arab, Polar, Szakal) were grown for 1–3 weeks in complete nutrient medium (+P) and without phosphate (-P). Pi concentration in plant tissues decreased strongly after culturing on -P medium. Pi deficit reduced shoot growth, stimulated root elongation and increased ratio of root/shoot in all oat cultivars. Pi deficit had a greater impact on growth of oat cv. Polar than other varieties. A decrease in the internal Pi status led to an increase of acid phosphatase activities in extracts from shoots and roots, and in root exudates.The highest activity of secreted APaseswas observed for oat cv. Arab, during the thirdweek of growth under Pi-deficient conditions. The activity of extracellular APase was high in young, growing zones of roots of -P plants.Histochemical visualization indicated high activity of APases in the epidermis and vascular tissues of -P plants. Pi deficiency increased intracellular APase activity in shoot mainly in oat cv. Polar,whereasAPase activity in rootswas the highest in oat cv. Szakal.Protein extracts fromroots and shoots were run on native discontinuous PAGE to determine which isoform(s) may be affected by Pi deficiency. Three major APase isoforms were detected in all oat plants; one was strongly induced by Pi deficit. The studied oat cultivars differed in terms of acclimation to deficiency of phosphate—used various pools of APases to acquire Pi fromexternal or internal sources.

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