Influence of Primary and/or Adventitious Root Systems on Wheat Production and Nutrient Uptake 1

Spring wheat ( Triticum aestivum “Thatcher”) was grown under greenhouse conditions to evaluate the importance of individual root systems under two levels of P and two soil water regimes in the fertilizer zone. A technique was developed whereby plants could be grown with complete root systems (primary plus adventitious), with only primary roots, or with only adventitious roots. Plants that developed only primary or only adventitious roots initiated late tillers just before reaching maturity. Since plants utilizing both root systems failed to initiate late tillers, it appears that late tillering is related to root development rather than to a soil water or P fertility factor. Early tillering under P fertilization was significantly greater when plants developed both root systems than when only primary or only adventitious roots were utilized. Phosphorus fertilization did not increase tiller formation unless both root systems were present. Grain yields were significantly greater when plants developed both root systems than when either individual root system was utilized. Plants with only adventitious roots yielded significantly more grain than those with primary roots only. This suggests that adventitious roots are more physiologically active than primary roots. Phosphorus fertilization significantly increased grain yields, irrespective of root development. The dry fertilizer zone resulted in decreased wheat yields when plants developed both root systems, but yields from plants with only primary roots were not affected by the dry fertilizer zone. Nitrogen and P translocation into the grain was significantly greater when plants developed both root systems than when plants were grown with incomplete root systems.