Carbohydrate activity regulation of floral quantity during the juvenile phase in black pepper (Piper nigrum L.)

Black pepper plants maintain synchronous vegetative growth and flowering during their lifetimes, even in the juvenile phase. How to limit the duration of flowering, facilitate a return to vegetative development should be studied. Light intensity has been reported to affect the levels of stored carbohydrates in some horticultural trees. However, it is unclear whether increased flowering intensity in adaptable light intensity is due to the regulation of carbohydrates in black pepper. Here, we report the characterization of carbohydrates and enzyme turnover in major source leaves under shading treatments during the juvenile phase of pepper. In addition to the previous finding that carbohydrate levels are correlated with flowering time, we report the novel finding that carbohydrate contents in the leaves control floral quantity. To gain insights into the underlying physiological mechanisms, we analyzed the effect of shading on sugar contents and floral transition, which revealed that shading regulated carbohydrate levels, an increase in starch accumulation improved floral quantity, and sucrose-starch ratio played a negative role in inflorescence quantity. Based on this analysis, we characterized the changes in enzyme activities in the leaves that affect carbohydrate dynamics and identified the key indicator enzymes and optimal shading intensity for the five developmental periods.