Sun Woo Chung

Changes in anthocyanidin and anthocyanin pigments in highbush blueberry ( Vaccinium corymbosum cv. Bluecrop) fruits during ripening

We monitored accumulation in terms of different types of anthocyanidin, in association with fruit skin coloration, in ‘Bluecrop’ highbush blueberry (Vaccinium corymbosum L.) at three stages of ripening: pale green, ca. 30 days after full bloom (DAFB); reddish purple, ca. 40 DAFB; and dark purple, ca. 50 DAFB. Total anthocyanin contents increased during ripening, while fruit skin color steadily became darker and bluer, as reflected in decreasing L* (a color space coordinate describing lightness) and b* (describing blue-yellow coloration). Of the six anthocyanidins commonly found in fruits, pelargonidin was absent throughout the ripening process. Cyanidin was first detected at the pale green stage. Peonidin, delphinidin, petunidin, and malvidin were first detected after fruits had passed through the reddish purple stage. The contents of delphinidin and malvidin increased more rapidly than those of other anthocyanidins, and were closely correlated with changes in fruit skin color, demonstrating that the types and quantities of anthocyanidins, which in turn form anthocyanins, were major determinants of fruit skin coloration. Four anthocyanins were detected at the reddish purple stage, and 22 were identified at the dark purple stage. All anthocyanins detected were glycosylated with glucose, galactose, or arabinose.

Photosynthetic acclimatisation of leaves in response to a shade-to-sun transition following summer pruning in peach (Prunus persica cv. Changhoweonhwangdo) trees

Summary Photosynthetic characteristics and the capacity for adaptation were examined in those leaves near to fruit that changed from shade to a high-light environment (shade-to-sun leaves) following summer pruning in 7-year-old ‘Changhoweonhwangdo’ peach (Prunus persica L.) trees. The shoots of the trees were topped, with a thinning-out of fruit in early-June, then 50% of the vigorous shoots were thinned-out between late-July and early-August, at the end of the rainy season. Summer pruning increased the penetration of light, subsequently increasing air and leaf temperatures, and decreasing the relative humidity in the lower parts of the canopy. The new high-light environment created by summer pruning did not affect the structural characteristics or pigment concentrations in shade-to-sun leaves. However, shade-to-sun leaves had a higher total carotenoid:total chlorophyll ratio compared to sun leaves, whereas this ratio decreased continuously in shade leaves. Shade-to-sun leaves required a period of time to adapt photosynthetically to the new high-light environment. Shade leaves had a lower photosynthetic capacity than sun leaves. The apparent quantum yield (Φpsii) and electron transport rate (ETR) of photosystem II (PSII), stomatal conductance (gs), and net CO2 assimilation rate (An) were lower in shade leaves than in sun leaves at the higher photosynthetic photon flux density. Shade-to-sun leaves did not recover, in terms of An, within 1 week from photo-inhibition caused by a lower Φpsii and ETR, although gs was higher in shade-to-sun leaves than in shade leaves. Four weeks after summer pruning, however, shade-to-sun leaves recovered in terms of their Φpsii, ETR, and An, all of which were higher than in shade leaves. Consequently, summer pruning in ‘Changhoweonhwangdo’ peach trees affected the photosynthetic rate and capacity of shade-to-sun leaves through a change in pigment composition rather than through structural adaptation to an improved light environment within the canopy, thereby influencing the characteristics of tree growth and fruit quality.