Biochemical changes during flowering in Citrus species

The present experiment was conducted during 2017–2018 with the objective to understand the relationship of seasonal changes in biochemical traits with the flowering behaviour of acid limes (Pusa Udit, Pusa Abhinav and ALC-29), lemons (Konkan Seedless, Kagzi Kalan and Hill lemon) and sweet oranges (Pusa Sharad, Pusa Round and Mosambi). Sweet oranges and Hill lemon expressed flowering once (February to March), and lemons and Acid limes bloomed almost round the year. In all lemons (except Hill lemon) and limes, protein level ≥ 9.30 mg g⁻¹ FW promoted the flowering, however, it was ≥ 19.3 mg g⁻¹ FW in Hill lemon and sweet oranges. In lemons and limes, superoxide dismutase (SOD) activity ≥ 9.88 Unit mg⁻¹ min⁻¹ TSP expressed the association with flowering except Pusa Abhinav lime. Hill lemon and sweet oranges bloomed at the activity of SOD ≥ 13.77 Unit mg⁻¹ min⁻¹ TSP. The catalase (CAT) activity did not follow a systematic pattern in most of the cultivars. In limes and lemons (except Hill lemon), the plants showing POX activity ≥ 17.77 μmol min⁻¹ mg⁻¹ total soluble proteins (TSP) showed flowering, while in rest of the genotypes, its level was ≥ 52.45 μmol min⁻¹ mg⁻¹ TSP to initiate the flowering. In most of the limes and lemons during August to February, ascorbate peroxidase (APOX) activity ≥ 0.20 μmol min⁻¹ mg⁻¹ TSP favoured the flowering, however, in Hill lemon and sweet oranges, it was ≥ 0.220 μmol min⁻¹ mg⁻¹ TSP. The lower activity of O₂⁻(0.91–1.76 μmol g⁻¹ FW) between August to January in limes and lemons (except Hill lemon) promoted the flowering.