Abstract: Due to a plenty of staminate flower differentiation, Zanthoxylum planispinum var. dintanensis, mainly reproduced by apomixis, was declined in the karst rocky desertification area of southwest Guizhou Province. However, the mechanisms involved in growth, fruiting, and nutrient characteristics of Z. planispinum var. dintanensis remain unclear. Here, we investigated the characteristics of shoot growth, biomass, nutrient contents of different organs in normal plants with pistillate flower (Np) and declined plants with staminate flower (Dp), to analyze the effects of plant decline on resource allocation among growth, nutrient storage, and reproduction. The results showed that fruit biomass of Np was significantly higher than that of Dp (P<0.05), whereas shoot and leaf biomass of Np was significantly lower than that of Dp. The contents of nitrogen, phosphorus, calcium, and soluble protein in staminate flower buds were significantly lower than those in pistillate flower buds (P<0.05), while the contents of calcium in flower buds were negatively correlated with the contents of nitrogen, phosphorus, potassium, and magnesium (P<0.01). Moreover, the length of pistillate inflorescence was significantly longer than that of staminate inflorescence, but shoot length and shoot number per bearing base branch in Np were significantly reduced. Although nutrient contents in root and stem of Np were significantly increased, crude protein content in seed was significantly lower than that of Dp. Our results indicated that Z. planispinum var. dintanensis with staminate flowers significantly altered resource allocation among growth, fruiting and nutrient storage, reflecting its adaptation to the nutrient stress environment in rocky desertification regions.

Key words: Zanthoxylum planispinum var. dintanensis, decline, staminate flower, resource allocation, nutrient characteristics