Sun/shade conditions and seedling recruitment in a cactus
Early life-history stages of cacti can benefit from the facilitative effects of nurse plants that reduce solar radiation and water stress. Miranda-Jácome et al. conduct a reciprocal transplant experiment, coupled with the artificial manipulation of sun/shade conditions, to test for the effects of local adaptation on germination, seedling survival and growth of the columnar cactus Pilosocereus leucocephalus. They find that significant local adaptation is mainly detected under full sunlight conditions, indicating that sun/shade acts as a selective agent in water-limited environments. Facilitation provided by nurse plants in these environments can attenuate the patterns of local adaptation among plants benefiting from nurse plant effects.
Image: Tennessee Valley Authority, 1942/ Franklin D. Roosevelt Presidential Library and Museum.
This month’s winner in the ‘so simple it’s positively brilliant (but why did nobody think of it before?)’ category is Damar López-Arredondo and Luis Herrera-Estrella’s paper entitled, ‘Engineering phosphorous [sic.] metabolism in plants to produce a dual fertilization and weed control system’.
Apart from the unusual spelling of phosphorus in the title (it is correct in the body of the article – and this is important since the study deals with two similarly worded phosphorus compounds: phosphate and phosphite!), this is a most interesting piece of research. I can do no better than reproduce the paper’s own rather elegant summary of the work (from Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, México) here: ‘High crop yields depend on the continuous input of orthophosphate (PO43–)-based fertilizers and herbicides. Two major challenges for agriculture are that phosphorus is a nonrenewable resource and that weeds have developed broad herbicide resistance. One strategy to overcome both problems is to engineer plants to outcompete weeds and microorganisms for limiting resources, thereby reducing the requirement for both fertilizers and herbicides. Plants and most microorganisms are unable to metabolize phosphite (PO33–), so we developed a dual fertilization and weed control system by generating transgenic plants [arabidopsis and tobacco] that can use phosphite as a sole phosphorus source. Under greenhouse conditions, these transgenic plants require 30–50% less phosphorus input when fertilized with phosphite to achieve similar productivity to that obtained by the same plants using orthophosphate fertilizer and, when in competition with weeds, accumulate 2–10 times greater biomass than when fertilized with orthophosphate’. Or, and in summary, ‘the production of transgenic crop plants able to utilize phosphite, together with the application of phosphite as a source of phosphorus, might potentially become an effective phosphorus-fertilization and weed control scheme in the almost 67% of cultivated land with low orthophosphate availability’.
Whilst the authors are appropriately – and understandably – cautious about the significance of the results and how well they will scale-up to field-sized trials, this work – from the country whose CIMMYT (The International Maize and Wheat Improvement Center) was a major player in the Green Revolution of the last century – sounds like another agronomic development with tremendous potential. ¡Muchas gracias!