Applications in sustainable production

Abstract

Low root temperature has previously been reported to induce boron (B) deficiency in some species but the mechanism is not entirely clear. Using B‐specific resin to buffer B concentrations in solution, we found that decreasing root zone temperature (RZT) from 27 to 12°C for 6 days depressed sunflower (Helianthus annuus L.) dry matter, root length, root to shoot ratio and B uptake. Boron uptake into the shoots was depressed at 12°C RZT to a greater relative extent than dry matter. Furthermore, B partitioning to young leaves decreased with low RZT, particularly at 12°C RZT. The external B requirement for shoot growth increased with low RZT. Leaf functioning was impaired by low B supply as measured by K+ leakage from the youngest mature leaf blade, whereas it was much less affected by RZT, and there was no effect of RZT on B ‐ adequate plants. By contrast, root function was impaired more by low RZT than low B. Therefore, we predict that higher rates of B application will be required for plant growth when soil temperature is below a critical threshold, which for sunflower was about 17°C. Conversely, practices which increase soil temperature above the threshold may also improve plant B nutrition.