Relative humidity around the fruit influences the mineral composition and incidence of blossom-end rot in sweet pepper fruit

Sweet pepper plants of cultivar Domino were grown using the hydroponic reci rculating nutrient film technique (NFT) at an EC of 2 dS m(-1) during the a utumn season. Two experiments examined the effects of relative humidity (r. h.) around the fruit on the accumulation of Ca, Mg and K on fruit of known age from date of anthesis. The humidity treatments used in the first experi ment were on average 30%, 50% and 80% and an ambient humidity achieved by c overing sweet pepper fruit with polyethylene bags containing 50 g each CaCl 2, NaCl or polyethylene bags without salts. The second experiment used an a irflow system to generate average r.h. levels of 20%, 40% and 80%. In both experiments high r.h. levels reduced the accumulation of Ca by the fruit. T he r.h. treatments particularly reduced the Ca concentration in the distal end of the fruit, which resulted in a higher incidence of blossom-end rot i n experiment I, and with no statistically significant effect in experiment II. The incidence appears to be related to the Ca concentration as well as the ratio of this element to Mg and K at the distal end. On the other hand, low r.h. promoted the accumulation of Ca in fruit particularly towards fru it maturity. R.h. had little effect on accumulation of Mg and K in sweet pe pper fruit and affected fruit mass only at maturity.