不同基因型柱花草的根系构型差异及其磷效率

柱花草是华南坡地果园生草栽培的重要草种,为减轻柱花草与果树的根系养分竞争,有必要筛选根系构型适宜的基因型柱花草。本试验在正常供磷条件下研究了7个基因型柱花草的根系构型特征,发现存在显著的差异,且总根长、主根长和根系表面积与生物量存在显著正相关。根据生物量和根系构型将其分为3类,选择生物量高但基根角度差异大的2个基因型(‘格拉姆’和‘184号’)进行进一步的磷效率比较研究,结果表明基根角度小的‘184号’在高磷条件下具有较高的磷吸收效率,但在低磷条件下的磷吸收效率较低,从而导致其磷效率较低。本研究表明,基根角度是影响磷吸收效率的重要因子,但是磷效率还取决于低磷条件下的生长表现;‘格拉姆’可能比‘184号’更适于用作果园间作。

Differences in root architecture of several Stylosanthes genotypes and their phosphorus efficiency

Stylosanthes is an important species for sod culture in orchards in south China. To alleviate nutrient competition by roots between Stylosanthes and fruit trees, it is necessary to screen Stylosanthes genotypes with appropriate root architecture. One experiment was conducted in specially designed rhizoboxes and another in pots. In the first experiment, the root architectures of seven Stylosanthes genotypes were investigated at normal P levels, and in the second experiment, P uptake efficiencies of two Stylosanthes genotypes with contrasting basal root angle were compared. Root architecture was characterized using scanning and WinRhizo analysis. There was a significant difference in root architecture among the seven genotypes. Plant biomass showed significant and positive relationships with total root length, tap root length, and root surface area. Based on plant biomass and root architecture, seven Stylosanthes genotypes were categorized into three classes. Two genotypes (‘Graham’ and ‘CIAT 184’) with high biomass and contrasting basal root angle were chosen for a further comparison of P efficiency. ‘CIAT 184’ had smaller basal root angles and a higher P uptake efficiency at high P level. However, at a low P level, P uptake efficiency was lower leading to a lower P efficiency. This study suggests that basal root angle is an important factor affecting P uptake efficiency, however, P efficiency also depends on plant growth performance at a low P level. ‘Graham’ is probably more suitable for inter-planting in orchards than ‘CIAT 184’.