Donald’s ideotype and growth redundancy: a pot experimental test using an old and a modern spring wheat cultivar

Human selection for high crop yield under water-limited conditions should have led modern cereal cultivars to invest less in root biomass, be it unconsciously. To test this hypothesis we conducted a pot experiment with two spring wheat cultivars, one old and one modern, both widely grown in the semi-arid regions of China. Using the replacement series method introduced by de Wit, we showed that the older landrace (Monkhead) was significantly more competitive than the more-modern cultivar (92-46). However, when grown in pure stand, old Monkhead had grown root biomass 3.5 times modern 92-46, whereas modern 92-46 gained a 20% higher grain yield. We also found modern 92-46 significantly increased root biomass per plant and root allocation (i.e., root biomass/total individual biomass) as its frequency in mixtures decreased, whereas old Monkhead did not respond in a similar way. This result suggests that the roots of modern cultivars may have gained an ability to recognize neighboring root sys...在水分受限条件下为追求作物高产而进行的人工选育，可能已在无意识间促使现代谷类作物品种减少了对根系生物量的投入。为验证这一假说，我们开展了盆栽试验，供试材料为两个在中国半干旱地区广泛种植的春小麦品种：一个为古老地方品种，另一个为现代栽培品种。采用de Wit提出的替代系列试验法，我们发现古老地方品种（Monkhead）的竞争能力显著强于现代栽培品种92-46。不过，在单一种植模式下，古老品种Monkhead的根系生物量是现代品种92-46的3.5倍，而现代品种92-46的籽粒产量却高出20%。我们还发现，随着现代品种92-46在混植群体中的占比降低，其单株根系生物量及根系分配比例（即根系生物量/单株总生物量）显著提升，而古老品种Monkhead并未出现类似响应。本研究结果表明，现代谷类品种的根系或许已演化出识别邻近根系的能力……