Typical and extremely hot summer conditions trigger a diverse response of phenolic metabolism in apple peel

摘要

The reaction of two apple cultivars ('Braeburn' and 'Golden Delicious') on dissimilar temperature conditions (SD1 - extremely high temperatures and SD2 - regular summer temperatures) was evaluated in terms of their phenolic accumulation. Total and photosynthetically active radiation as well as air and fruit temperatures were higher on SD1. Fruit temperature was approx. 10 degrees C higher on SD1 in comparison to SD2. Significant differences in phenolic content levels were detected between the two sampling days. Higher amounts of hydroxycinnamic acids, flavonols, flavanols and dihydrochalcones were measured in sunburned (SB) and healthy sun exposed (HS) 'Golden Delicious' apples on SD1 compared to SD2. The differences in phenolic content were less prominent in `Braeburn' peel sampled on both sampling dates. Differences in phenolic accumulation were also determined between morning (7 am) and afternoon (1 pm) samplings but the changes were less uniform and only significant in 'Braeburn' HS peel and 'Golden Delicious' SB peel. No changes in phenolic content levels have been detected in apples inside the tree crown on different sampling dates and hours of the day.