Phenolic compounds in young developing kiwifruit in relation to light exposure: Implications for fruit calcium accumulation

Abstract

The interaction between light availability and the biosynthesis of phenolic compounds in fruit of kiwifruit (Actinidia deliciosa var. deliciosa , C.F. Liang et A. R. Ferguson) was investigated. Fruits were exposed either to natural light or were artificially shaded while growing on mature vines and were analysed weekly during the first 11 weeks of development. Phenols were identified and quantified by using High Performance Liquid Chromatography (HPLC). Results showed that the predominant phenolic compounds were hydroxycinnamic acids (HCAs), flavonols and the flavan 3-ol epicatechin. Calcium (Ca 2' ), the main mineral nutrient involved in fruit quality was also determined. Light significantly increased the accumulation of both phenols and Ca 2' into the fruit. This work expands the list of known phenolics in kiwifruit and provides a possible explanation for the seasonal pattern of Ca 2' import into the fruit. Results on light Áphenol interaction being apparently beneficial for fruit Ca 2' accumulation, suggest that accurate canopy management could enhance fruit quality.

Characterisation of the Polyphenol Content in the Kiwifruit (Actinidia deliciosa) Exocarp for the Calibration of a Fruit‐sorting Optical Sensor

“…In particular, considering the mean values, the flavonols in fruits under full sun were 63.5% and 38.5% higher than the shade and mid‐shade samples, respectively, as expected on the basis of their protective role in plants (Agati and Tattini, ). A light‐induced increase in phenolic compounds of kiwifruit stalk was previously observed, but unfortunately the authors did not analyse the phenolic content in the fruit exocarps (Montanaro et al ., ). It is well known that the activity of the key enzymes in the polyphenol biosynthetic pathway is stimulated by light exposure.…”

“…The kiwifruit quality depends on several factors such as ripening time, genotype, cultivation techniques and environmental conditions (Kempler et al ., ; Snelgar et al ., ; Ferguson, ). The polyphenol content of kiwifruits was also influenced by light exposure, harvest time and storage conditions during the post‐harvest (Montanaro et al ., ; Tavarini et al ., ).…”

Fruit Calcium: Transport and Physiology

“…CME induced reductions in basipetal IAA efflux were only observed in tomato fruit grown under high salinity conditions where calcium uptake was reduced ( Brown and Ho, 1993 ). In kiwifruit, light induction of higher levels of auxin-protecting hydroxycinnamic acids decreased auxin degradation, resulting in increased calcium uptake ( Montanaro et al, 2007 ). These results suggest that tomato susceptibility to blossom end rot may be determined not just by differences in capacity for calcium uptake and distribution, but also by related factors such as auxin transport and metabolism, and rate of cell enlargement ( Bangerth, 1976 ).…”

Internal versus external control of calcium nutrition in kiwifruit

“…The beneficial effect of higher irradiance on Ca nutrition has been attributed to a light‐induced increase in vascular development within the fruit pedicel and berry ( Biasi and Altamura , 1996) possibly due to increased concentration of some secondary metabolites involved in the xylogenesis pathway ( Montanaro et al, 2007). However, the direct role of light as a driving force for fruit transpiration (see Nobel , 2005) in kiwifruit was examined in a modeling exercise and found to be not significant because most of transpiration changes are related to variations of air temperature and relative humidity to which light is intimately correlated ( Montanaro et al, 2012).…”

“…, Italy), conventional orchard management includes frequent tillage to minimize competition for water between the crop and the spontaneous weeds ( Testolin and Ferguson , 2009). This practice causes a reduction in root density in the upper soil layer ( Montanaro et al, 2007) where available Ca is higher ( Jobbágy and Jackson , 2001), hence, tillage may have a negative impact on Ca absorption. Calcium may also be accumulated at the root apex in specialized cells that serve initially as a Ca sink and then by remobilization as a Ca source, thereby accommodating Ca demand from cell differentiation and root elongation ( Storey et al, 2003).…”