Standing crops and nutrient attributes of litchi (Litchi chinensis) floral nectar in response to the removal of inflorescences

Litchi inflorescences bear hundreds of small flowers, but most flowers need to be removed to reduce the consumption of carbohydrates and increase fruit setting. The production and secretion of nectar are largely affected by the availability and metabolism of carbohydrates. However, the secretion pattern and constituents of litchi nectar in response to the removal of inflorescences are unclear. Here, we showed that the litchi nectar secretion amount ranged from 4 to 10 mg per flower with the cultivar ‘Nuomici’ having the strongest secretion ability. The concentration of total soluble solids in litchi nectar was approximately 30%. Fructose was present in the highest concentration in nectar, followed by glucose and sucrose. Cultivar, flower sex and inflorescence-removal treatment had no significant main effect on soluble sugars but had two-way interaction effects on sucrose. Twenty-seven amino acids were detected, including seven essential amino acids. The concentration of amino acids was significantly affected by cultivar and flower sex, with nectar from the cultivar ‘Guiwei’ and male flowers having a significantly higher concentration. Removal of inflorescences did not show the main effect on the nectar amount, total soluble solids, or protein contents, but had interactive effects on the concentration of sucrose and amino acids.