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Lemon (Citrus limon L.) is one of the most cultivated citrus fruit in South Africa. In citrus packhouses, fruit are coated with commercial synthetic waxes to enhance shelflife. However, the use of waxes has been linked to peteca spot (PS) incidence in lemons. This study evaluated the efficacy of chitosan (CH) and carboxymethyl cellulose (CMC) incorporated with moringa leaf extracts (M) on reducing peteca spot incidence on 'Eureka' lemon. A total of 500 'Eureka' lemons were harvested from outside and inside canopy positions from a commercial orchard in KwaZulu-Natal, South Africa. Fruit were assigned to five coating treatments, namely; control, 1% M + CMC, 1% CMC, 1% CH and 1% M + CH. After coating, fruit were transferred into a cold room with delivery air temperature set at 3 °C for 12 weeks to induce the disorder. At each sampling week, peteca spot incidence, fruit physicochemical and phytochemical properties including color, mass, vitamin C, carotenoids, TSS, TA and phenolics were measured. The results showed that coating treatments and canopy position significantly affected PS incidence. Fruit coated with M + CMC, CMC, CH were less susceptible to PS development in both inside and outside canopy compared to the control and M + CH coated fruit. Coating treatments significantly affected phenolic and flavonoid concentration. Moreover, coating treatments significantly reduced mass loss, ascorbic acid loss and delayed color change of fruit. The results found in this study demonstrated the ability of either M + CMC, CMC, or CH as coating treatments for reducing PS in 'Eureka' lemon. [ABSTRACT FROM AUTHOR]

Key message: Across sites in Brazil and Hawaii, LMA and N were strongly correlated with height and shade index, respectively, which may help simplify canopy function modeling of Eucalyptus plantations. Abstract: Within tree canopies, leaf mass per area (LMA) and leaf nitrogen per unit area ( N) commonly increase with height. Previous research has suggested that these patterns occur as a strategy to optimize carbon gain by allocating available resources to upper canopy leaves that are exposed to greater light availability. We tested three hypotheses about the influences of height, shade index (a proxy for light), and stand age on LMA and leaf nitrogen for even-aged Eucalyptus saligna and Eucalyptus grandis × urophylla plantations in Brazil and Hawaii, USA, spanning most of the environmental conditions found across 19.6 million ha of Eucalyptus spp. plantations around the world. Shade index was developed by incorporating canopy depth (inner-crown shading) and a tree height ratio relative to neighbor trees (shading from other trees). Across all sites and ages, leaf height accounted for 45 % of the variation in LMA, whereas shade index accounted for only 6 %. A combination of both factors was slightly better in accounting for LMA variation than height alone. LMA-height relationships among sites were strongest under greater light availability and in older stands. Leaf nitrogen per unit mass ( N) consistently decreased with shade index, whereas N showed no consistent pattern with height or shade index. These relationships indicate that N is primarily driven by light, while height is the primary driver for LMA. The general relationships between LMA and leaf N across all sites may simplify canopy function modeling of E. saligna and E. grandis × urophylla plantations. [ABSTRACT FROM AUTHOR]

We investigated the seasonal variation in the gas exchange of current and 1-year-old needles in the upper sun and lower shade crown of adult Pinus canariensis trees. In general, current year needles displayed lower gas exchange rates than the 1-year-old needles. In both needle age classes, gas exchange was significantly lower in the shade than in the sun crown. However irrespective of crown position and needle age, maximum daily net photosynthesis, transpiration, and stomatal conductance for water vapour were generally higher during the wet and cold winter as compared to the dry and hot summer. These higher gas exchange values obtained during the cold and wet season can mainly be explained by higher soil-water availability and lower evaporative demand as compared to the warm and dry seaon. In addition, we also observed a displacement in the temperature optimum of net photosynthesis towards lower temperatures during the cold and wet season as compared to the warm and dry season. The observed gas exchange characteristics indicate a conservative water saving strategy and thus allowing P. canariensis needles to maintain a positive carbon gain even at periods of high evaporative demand and low soil-water availability. [ABSTRACT FROM AUTHOR]