Increased transpiration is correlated with reduced boron deficiency symptoms in the maize tassel-less1 mutant

Loss-of-function mutations of the tassel-less1 (tls1) gene in maize, which is the co-ortholog of the Arabidopsis boron (B) importer NIP5;1, leads to the loss of reproductive structures (tassels and ears). The tls1 phenotypes can be rescued by B supplementation in the field and in the greenhouse. As the rescue with B supplementation is variable in the field, we investigated additional abiotic factors, potentially causing this variation in controlled greenhouse conditions. We found that the B-dependent rescue of the tls1 mutant tassel phenotype was enhanced when plants were grown with a mix of high pressure sodium (HPS) and metal halide (MH) lamps. Normal and tls1 plants had a significant increase in transpiration and increased B content in the leaves in the greenhouse with the addition of MH lamps. Our findings imply that B transport to the shoot is enhanced through increased transpiration, which suggests that the xylem transpiration stream provides a significant supply of B in maize.