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South African Journal of Botany
Elsevier
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Abstract: |
Honey, pomegranate juice, and lemon juice are natural plant growth biostimulators that contain many bioactive substances that play essential roles in many plants’ physio-biochemical processes, and development. The
objectives of this research were to explore how foliar spraying with a 5 % or 10 % diluted pomegranate juice
solution (DPJS), a 5 % or 10 % diluted lemon juice solution (DLJS), or a 5 % or 10 % diluted honey solution
(BHS), versus a control (distilled water; D-H2O), positively influenced the growth, pharmaceutical, and ornamental qualities of calendula (Calendula officinalis L.) plants in both the 2021/2022 and 2022/2023 seasons.
Foliar spraying with 5 %- or 10 %-DPJS, 5 %- or 10 %-DLJS, or 5 %- or 10 %-BHS significantly increased photosynthesis-related assessments (total chlorophyll and carotenoid contents, the maximum quantum efficiency
of photosystem II (Fv/Fm), and net CO2 assimilation), water use efficiency, RubisCO content and activity,
RubisCO gene expression, and sugar fraction (glucose, sucrose, and starch contents). Also, osmoregulatory
compounds (K+, total soluble sugars, and glycine betaine contents), antioxidant capacity (in terms of total flavonoid, anthocyanin, proline, ascorbate, and glutathione contents), nutrient and hormonal contents were significantly increased by foliar spraying of all the above-mentioned treatments. These positive findings were
noticeably reflected in improved growth (fresh and dry plant weights), inflorescence traits (number of inflorescences on plant, fresh and dry petal weights, petal content of soluble sugars, ß-carotene, and total carotenoids), and longevity of inflorescence (vase life and water uptake by inflorescences), while electrolyte
leakage and abscisic acid were noticeably decreased compared to foliar spraying with D-H2O. The secondbest treatment was 5 %-DPJS or 10 %-BHS, and they were preceded by 5 %-BHS as the best treatment, which
the research results recommended applying in the field to obtain the best pharmaceutical and ornamental
qualities of calendula
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