Absorption and Distribution of Calcium (45Ca) Applied to the Surface of Orange (Citrus sinensis) Fruits at Different Developmental Stages

Abstract

In this study, the rate of absorption and transport of calcium (Ca) in orange fruits (Citrus sinensis cv. Fukumoto) after surface treatment with 45Ca was evaluated by supplying treatments at different dates between fruit set and mid-phase II of growth (i.e., 30, 44, 66 and 99 days after full bloom, DAFB). 45Ca absorption was always detected, but 45Ca application at the fruit set was associated with the highest rates of Ca transport into the pulp (39%) compared to the other treatments (17–19%). Scanning electron microscopy SEM) images of the fruit surface showed the occurrence of stomata along with the entire rind at all the developmental stages evaluated. However, from the beginning of stage I, stomata began to collapse and develop plugs, and this became frequent as the fruit age increased. From 44 DAFB, oil gland density increased, and Ca oxalates (CaOx) were found in the fruit flavedo and albedo. Fruit Ca (not labeled) concentration increased from fruit set (30 DAFB) to 99 DAFB, although oil gland formation and rind growth and differentiation likely hindered Ca transport to internal fruit tissues (pulp). The total Ca concentration in the pedicel was always higher than that in the fruit, with no differences between the first three treatments. The information obtained in this study may be essential for improving Ca fertilizer efficacy in citrus by spray applications.

Effect of calcium on fruit quality: A review

“…The absorption peaks at 38 DAFB and may be antagonistic with nutrients such as potassium (K + ), ammonium (NH 4 + ), and magnesium (Mg 2+ ) at the early stage of fruit development. Similarly, Bonomelli et al (2022) find significant differences in calcium distribution in orange (Citrus sinensis) fruits cv. 'Fukumoto' with applications at various stages of development (30 DAFB, 44 DAFB, 66 DAFB, and 99 DAFB).…”

“…Additionally, the influence of Ca on the contents of endogenous growth substances, especially cytokinins, has been reported (Ali et al, 2021). In this context, Bonomelli et al (2022) found that early applications of Ca were more effective in increasing the dry mass of orange fruits.…”

“…Calcium is more abundant in older leaves, and a deficiency of calcium is common in fruits, young leaves, and storage organs (Prado, 2021). In fruits, a deficiency of calcium is attributed to the reduced number of stomata, impeding the transport of calcium through the xylem (Bonomelli et al, 2022). Plant absorption of Ca 2+ is faster during the initial stages of fruit growth (Casero et al, 2017), as it serves as an enzyme activator and an essential element for cell division, cell elongation, and growth (Prado, 2021).…”

Effect of Calcium Fertilization on Calcium Uptake and Its Partitioning in Citrus Trees

“…In these organs, the higher Ca concentration in T1-Ca resulted in significant variations in Ca content compared to T2 trees, with no differences in biomass among treatments. According to Bonomelli et al [35], during fruit set, more Ca transport to the fruit pulp occurs (up to 39% of applied 45 Ca). However, as the fruit grows, more Ca is retained in the calyx zone, which decreases the rise in Ca in fruit (between 17 and 19% of applied 45 Ca).…”

“…We are able to ascertain this based on the use of labeled fertilizers with 44 Ca. In citrus fruit, the uptake and distribution of Ca deriving from fertilizers in "Clemenules" and "Fukumoto" mandarin trees have been studied using the isotope labeling technique with radioactive isotope 45 Ca [34,35]. This approach opens new possibilities for gathering insights into calcium nutrition in crops, offering a valuable alternative to radioactive isotopes.…”