Relationship between photosynthetic efficiency and maturity of ‘Lamb Hass’ avocado fruit

S. Mwelase, A. Mditshwa, L.S. Magwaza, S.Z. Tesfay, J. Mashilo
Individual avocado fruit requires high energy input during growth and development for the biosynthesis of the fruit’s high oil content and dry matter. This energy is provided by carbohydrates derived from photosynthesis. Therefore, changes in leaf photosynthetic capacity may directly affect avocado fruit maturity. The objective of this study was to evaluate the differences in photosynthetic efficiency of outside and inside canopy leaves of ‘Lamb Hass’ avocado and how such changes are associated with fruit maturity. The experiment was carried out during the 2018/2019 growing season at Everdon Estates, a commercial avocado orchard of Westfalia fruit in KwaZulu-Natal Midlands, South Africa. Gas exchange and chlorophyll fluorescence parameters such as photosynthetic rate (A), stomatal conductance (gs), transpiration rate (T), effective quantum efficiency of photosystem II photochemistry (ΦPSII), electron transpiration rate (ETR), photochemical quenching (qP), non-photochemical quenching (qN), and fruit maturity parameters including the mesocarp moisture content (MC), mesocarp dry matter content (DM) and mesocarp oil content (OC) were evaluated during the season. Results showed that leaves from the outside canopy position had higher A (25.17 μmol CO2 m‑2 s‑1), gs (3.76 mmol m‑2 s‑1), qP (0.54), ФPS II (0.30) than leaves inside the canopy (A=17.44 μmol CO2 m‑2 s‑1, gs=2.17 mmol m‑2 s‑1, qP=0.07 and ФPSII=0.04. Fruit maturity also differed significantly with canopy position, with the outside canopy fruit having higher DM, OC, and lower MC (20.96, 6.50 and 79.04%, respectively) than the inside canopy fruit (19.23, 5.25 and 80.77%, respectively). qP, ФPSII and ETR positively and significantly correlated with DM and OC but negatively and significantly correlated with MC. Further, qN was negatively and significantly correlated with DM and OC but positively and significantly correlated with MC. These findings indicate that the high photosynthetic capacity of the outside canopy is likely to result in more DM accumulation and oil synthesis in the outside canopy fruit than inside the canopy.
Mwelase, S., Mditshwa, A., Magwaza, L.S., Tesfay, S.Z. and Mashilo, J. (2022). Relationship between photosynthetic efficiency and maturity of ‘Lamb Hass’ avocado fruit. Acta Hortic. 1349, 85-94
DOI: 10.17660/ActaHortic.2022.1349.13
https://doi.org/10.17660/ActaHortic.2022.1349.13
maturity, physiology, photochemistry, canopy position
English

Acta Horticulturae