Effects of phosphorous supply on growth, phosphate distribution and expression of transporter genes in tomato plants

Abstract

Phosphorus (P) is absorbed only as phosphate ions (Pi), which are often lower than the plant needs in cultivated soils. In this research, we have used various amounts of Pi for four weeks to feed hydroponically young tomato plants. Pi treatments influenced growth, biomass production, P levels in different tissues and the expression pattern of two Pi transporter genes, LePT1and LePT2. In a low Pi concentration density and length of root hairs, total root length, specific root length and root to shoot ratio increased while biomass, leaf area, and root density decreased. Root morphology was not changed significantly when the Pi supply was 0.5 mM or higher. The P level in roots or shoots did not increase significantly, when Pi level was above 1 mM. Correlation between roots, P content and two Pi transporter activities showed that transcription of LePT2 is induced at 0.2 g P/100g-1 dry weight in roots while LePT1expression remains high, up to 0.5 g P/100g-1 of dry weight. In total, these results showed that the P content of roots and shoots are strongly correlated with supplied Pi concentrations. Allocating more P in shoots than in roots indicated that leaves are cumulating organ for P distribution at high Pi condition.