Ultraviolet radiation effects on fruit surface respiration and chlorophyll fluorescence

• Published in: The journal of horticultural science & biotechnology 2008, Vol.83 (1), p.43-50
• Main Authors: Glenn, D.M, Wunsche, J, McIvor, I, Nissen, R, George, A
• Format: Article
• Language: English
• Subjects: apples; cell respiration; chlorophyll; fluorescence; fruit crops; fruit surface respiration; fruit surface temperature; fruits (plant anatomy); Malus domestica; photosynthesis; photosystem II; solar radiation; temperature; tropical and subtropical fruits; ultraviolet radiation
• ISSN: 1462-0316; 2380-4084
• DOI: 10.1080/14620316.2008.11512345

High-value fruit crops are exposed to a range of environmental conditions that can reduce fruit quality. Solar injury (SI) or sunburn is a common disorder in tropical, subtropical and temperate climates and is related to: 1) high fruit surface temperature, 2) high visible light intensity, and 3) ultraviolet radiation (UV). Positional changes in fruit due to increased weight or abrupt changes due to summer pruning, limb breakage or other damage to the canopy can expose fruit to high solar radiation levels, increased fruit surface temperature and increased UV exposure that are higher than the conditions to which they are adapted. In this work, we examined the interaction of high fruit surface temperature, saturating photosynthetically active radiation (PAR) and short term UV exposure on chlorophyll fluorescence, respiration, and photosynthesis of fruit peel tissues from tropical and temperate fruit as a simulation of these acute environmental changes. All tropical fruit (citrus, macadamia, avocado, pineapple and custard apple) and the apple cultivars: 'Gala', 'Gold Rush', and 'Granny Smith', increased dark respiration, Ao, when challenged with UV suggesting that UV repair mechanisms are induced. Maximum quantum efficiency of photosystem II ( FvFm ) and quantum efficiency of photosystem II ( Psi II ) were unaffected indicating no adverse effects on photosystem II (PSII). In contrast, 'Braeburn' apple had reduced Fv/Fm with no increase in Ao at all sampling dates. There was a consistent pattern in all studies: when Fv/Fm was unaffected by the UV treatment, Ao was significantly increased. Conversely, when Fv/Fm was reduced by the UV treatment, then Ao was unaffected. The pattern suggests that when UV repair mechanisms are effective, PSII is adequately protected and the protection occurs at the cost of higher respiration. However, when the UV repair mechanisms are ineffective, not only is PSII damaged, but there is additional short term damage to the repair mechanisms indicated by a lack of respiration to provide energy.