Physiology of flowering in Citrus species

Abstract

An experiment was conducted on the trees 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) during 2017-18 with the objectives to understand the relationship of seasonal changes in physio-biochemical traits with the flowering behaviour of citrus species. Sweet oranges and Hill lemon expressed flowering once in a year (February to March), while lemons and acid limes bloomed almost round the year. The flowering genotypes showed lower value of photosynthetic rate (A) than non-flowering genotypes. C:N ratio ≥ 5.57 could initiate the flowering in lemon (except Hill lemon) and limes, while in other genotypes, it was ≥ 13.39 for flowering. In sweet orange and Hill lemon, GA3 followed an upward trend till January, and declined thereafter, however, the trend was reverse in other genotypes till December. During spring season, the trees having GA3 ranging between 0.12-0.93 mg g-1 FW showed the flowering. The content of free amino acids (FAA) increased till February and declined thereafter. Overall the level of FAA ≥ 10 mg g-1 FW proved to be the critical level to induce flowering in all the genotypes tested. The level of total antioxidant capacity (TAC) ≥ 18.12 μmol g-1 FW favoured the flowering in all citrus genotypes tested. Overall low level (96.45-108.27 mmol H2O2 mg-1 FW) of hydrogen peroxide (H2O2) favoured the flowering.