Search

* Premise of the study: Border cells, which separate from the root cap, can comprise >90% of carbon-based exudates released into the rhizosphere, but may not provide a general source of nutrients for soil microorganisms. Instead, this population of specialized cells appears to function in defense of the root tip by an extracellular trapping process similar to that of mammalian white blood cells. Border cell production is tightly regulated, and direct tests of their impact on crop production have been hindered by lack of intraspecies variation. * Methods: Border cell number, viability, and clumping were compared among 22 cotton cultivars. Slime layer "extracellular trap" production by border cells in response to copper chloride, an elicitor of plant defenses, was compared in two cultivars with divergent border cell production. Trapping of bacteria by border cells in these lines also was measured. * Key results: Emerging roots of some cultivars produced more than 20000 border cells per root, a 100% increase over previ ously reported values for this species. No differences in border cell morphology, viability, or clumping were found. Copper chloride-induced extracellular trap formation by border cells from a cultivar that produced 27921 ±2111 cells per root was similar to that of cells from a cultivar with 10002 ±614 cells, but bacterial trapping was reduced. * Conclusions: Intraspecific variation in border cell production provides a tool to measure their impact on plant development in the laboratory, greenhouse, and field. Further research is needed to determine the basis for this variation, and its impact on rhizosphere community structure. [ABSTRACT FROM AUTHOR]

Here we describe the use of Pisum sativum L. as a model system to measure how short-term treatment of root tips with soluble metabolites can influence root growth and release of root exudates. The results revealed that even a 3-minute exposure of root tips to metabolites normally released from roots into the rhizosphere (e.g. rhamnose, ferulic acid, salicylic acid) can significantly influence root growth without affecting production of border cells and associated exudates. Conversely, products including caffeine, saccharide lactone, and pisatin alter production of border cells, without affecting root growth. Understanding how root-derived and exogenous metabolites can selectively impact root function may yield benefits in crop production, especially in greenhouse agriculture systems where growing roots can be exposed to a significant accumulation of plant exudates. [ABSTRACT FROM AUTHOR]