Abstract
We studied the effect of differential phosphorus (P) supply on the development of oat seedlings (<em>Avena sativa</em> L. ‘Arab’) as well as localization and activity of acid phosphatases in tissues and root exudates. Plants were grown for 1–3 weeks on nutrient media with inorganic phosphate (+P, control), reduced Pi (0.1 P), phytic acid (PA) as organic P source, and without P addition (−P), in standard conditions or in a split-root culture system. Phosphate starvation reduced shoot growth but increased root elongation and root/shoot ratio, whereas 0.1 P and PA oat plants had similar growth parameters to +P plants. The growth on −P medium significantly decreased Pi content in all tissues, but only a slight Pi decrease was observed in plants grown on 0.1 P and PA media or various split-root system conditions. Pi starvation led to an increase in acid phosphatase (APase) activity in root exudates when compared to +P, 0.1 P, and PA plant samples. APase activity was especially intensive in root cross sections in rhizodermis and around/in vascular tissues of −P plants. For plants grown on 0.1 P medium and on phytic acid, APase activity did not change when compared to the control. Three major isoforms of APases were detected in plant tissues (similar in all studied conditions, with a higher activity of one isoform under Pi deficit). Generally, lowered Pi content (0.1 P) was not stressful to oat plants for up to 3 weeks of culture. Oat plants grew equally well on nutrient media with Pi and on media with phytate, although phytate was considered not available for other plants. The oat plants activated mainly extracellular APases, but also intracellular enzymes, rather via nonlocal signals, to acquire Pi from external/internal sources under Pi deficiency.
Highlights
Phosphorus is a critical macronutrient required for plant development and metabolism, including processes such as organic compound biosynthesis, photosynthesis, respiration, energy transfer, coordination of gene expression and enzymes activity, or signal transduction [1,2,3,4,5]
Oat culture in split-root system conditions, when half of the root system was exposed to −P nutrient medium, while other part of the root system was in +P solution, did not significantly affect the activity of extracellular acid phosphatase (APase), which can suggest that the induction and secretion of APases from oat roots is not a local response to Pi depletion in the ground
Our study indicates that phytate can provide a good source of P for sustained growth of oat (Avena sativa L.) in phytate-rich environments
Summary
Phosphorus is a critical macronutrient required for plant development and metabolism, including processes such as organic compound biosynthesis, photosynthesis, respiration, energy transfer, coordination of gene expression and enzymes activity, or signal transduction [1,2,3,4,5]. The P availability is one of the most limiting factors for crop plant growth and yield production, mainly due to its immobilization. Phosphorus in soil exists predominantly as sparingly soluble inorganic phosphates and insoluble organic phosphates, which are not directly available to plants. The available forms of P are H2PO4− and HPO3− ions (Pi), usually present in the soil solution in very small concentrations [6]. Plants have evolved various morphological, physiological, and biochemical adaptations to counteract phosphate deficiency.
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