Phosphate-starvation response of cereal plants: add phosphatase activity and growth changes

摘要

Phosphate deficiency effects on the plant growth and acid phosphatase activities in the tissues of rye (Secale cereale L.), wheat (Triticum vulgare L.), oat (Avena sativa L.) and barley (Hordeum vulgare L.) were investigated. Plants were cultured hydroponically in a complete nutrient medium (+P, control) or without phosphate (-P). The growth in the -P nutrient medium significantly affected the inorganic phosphate (Pi) concentration in leaves and roots of all plants studied. Phosphate starvation decreased growth of shoots and often also the mass of the roots; however the root/shoot ratio was always higher for -P plants. The root elongation growth was enhanced under Pi deficiency conditions; in -P oat and barley, more intensive elongation of the roots was observed than in other plants, especially after 3 weeks growth on nutrient media, On the other hand, inhibition of the shoot growth was more pronounced for rye and wheat, cultured on a Pi-deficient medium. A decrease in the internal Pi status led to an increase of acid phosphatase activities both in extracts from the roots and in root exudates when compared to samples from the Pi-sufficient plants. An increase of activity of the root surface acid phosphatase was the highest for the Pi-deficient rye and wheat, after 2-3 weeks of culture in the -P medium. Increase of acid phosphatase activities secreted by the roots of -P cereal plants was higher than those of intracellular acid phosphatase. The comparison of the studied plant responses to Pi-starvation suggests that wheat is more sensitive to the lack of Pi at the early stages of growth, whereas oat (and perhaps barley) is more resistant to Pi deficiency than other plants. The results confirm the important role of root secretion of acid phosphatases in acquiring phosphorus from the nutrient-limited soil and in acclimation of cereal plants to moderate Pi deficiency.