Abstract: Hypocotyl is a unique propagator of viviparous mangrove species such as Kandelia obovata. Understanding the geographical variations in the phenotypic traits of hypocotyls and seedlings of K. obovatawith different provenances, as well as the differences in nutrition requirements is critical for both conservation and genetic breeding of this valuable mangrove species. In this study, we collected mature hypocotyls of K. obovata of 11 provenances from five provinces in China. Based on their hypocotyl traits, we planted seedlings from 11 provenances at the Jingshanexperimental testing site in Zhejiang Province, and monitored their growth traits. Geographic variations of hypocotyls and seedlings were quantitatively analyzed through ANOVA, correlation analysis, and cluster analysis. We found that the phenotypic traits and nutrient contents of hypocotyls among the provenances were significantly different. In addition to carbon content and basal diameter, the coefficient of variations for various traits among the provenances was higher than those within the provenances, with the repeatability of the trait being higher than 85%. Hypocotyl length, height growth and biomass showed significant negative correlations with latitude and longitude, while they were positively correlated with mean annual temperature. Nitrogen and phosphorus contents showed opposite trends. There were positive correlations between: top diameter of hypocotyl and annual mean temperature, basal diameter of hypocotyl and annual mean temperature, and hypocotyl length and mean annual rainfall. Hierarchical cluster analysis further revealed that the 11 provenances could be classified into three groups: (1) HK and ZJ; (2) FD, YQ and CN; (3) BH, FCG, SZ, YX, LH and QZ. Clearly, there were large variations in phenotypic traits in K. obovata provenances, with each trait being subjected to strong genetic control. The 11 provenances of K. obovata were also clustered into three groups with distinct geographic features. The hypocotyl size and seedling growth were negatively correlated with the nitrogen and phosphorus contents of hypocotyl.

Key words: tillage practice, nutrient management, weed community, biodiversity.