Abstract
Winter oilseed rape (Brassica napus L.) is a major crop in the middle and lower Yangtse river basin, China, where boron (B) deficient soils are widespread. Appearance of B deficiency in oilseed rape often coincides with cold weather during its winter growth. To understand effects of cold weather on plant response to low soil B, a field experiment with oilseed rape cv. Zheyouyou 2 grown in a red soil with low B availability was conducted in Zhejiang province, China. Canopy covers made from transparent plastic sheets were used only at night to modify the microclimate during the early reproductive growth between pre-exposure of flower buds and green bud stage. Canopy treatment (T) increased the minimum air temperature inside the cover by up to 1.5°C when the minimum air temperature in the open was below O°C in early February. Covering plants for 15 days in early February strongly increased shoot dry weight at all levels of B supply. That covering plants increased shoot dry weight of B deficient plants without increasing their leaf B concentration suggests that internal B requirements were decreased. However, because later plant responses at maturity gave contradictory responses, it was concluded that further study of low temperature X B interactions need to be done in controlled environments.