The effect of selenium on growth, photosynthesis and activity of acid phosphatase in garlic (Allium sativum L.) plants under phosphorus deficiency and mycorrhizal colonization

Garlic (Allium sativum L.) is susceptible to phosphorus (P) deficiency and because of coarse root system with low branching rate, this species is highly dependent on mycorrhizal symbiosis. As a beneficial element for higher plants, selenium (Se) improves nutritional and pharmaceutical quality of this species. In this research, the effect of Se (at 0, 20 and 80 µg L–1 of substrate as Na2SeO4) was investigated in garlic plants grown under adequate (2 mM) and low P (without P supply for six weeks) in the absence or presence of arbuscular mycorrhizal fungus (AMF), Diversispora versiformis in perlite as substrate and irrigated with Hoagland nutrient solution for six weeks. Results showed that, P deficiency caused reduction of shoot growth and leaf photosynthesis while AMF inoculation results in the improvement of growth, photosynthesis and sugars content. Selenium augmented the effect of AMF inoculation leading to the highest dry biomass, photosynthesis and sugars content under the combination of both treatments irrespective the P supply level. The root activity of acid phosphatase (APase) was not affected by low P or +AMF as single treatments, while Se alone or in combination with low P and +AMF significantly increased the APase activity. The optimum Se concentration on the biomass, root colonization rate, photosynthesis and APase activity was 80 µg L–1. This is the first report on the synergistic effect of Se on AMF symbiosis on the adaptive response of plants to P deficiency.