ABSTRACT
BACKGROUND: Conservation tillage promotes the accretion of soil organic matter and often leads to improved soil fertility and moisture availability. However, few studies have looked at the physiological response of crop plants to different tillage practices. It was therefore hypothesised that measuring the nutrient concentrations and stable isotope composition (δ(13)C, δ(18)O, δ(15)N) of shoots could help evaluate the physiological response of common bean (Phaseolus vulgaris L.) to different tillage treatments (no tillage (NT) and mouldboard ploughing (MP)) in a rain-fed farming system in northern Mexico. RESULTS: NT significantly enhanced shoot phosphorus concentration in bean plants. Tillage exerted a negative effect on the extent of root colonisation (%) by arbuscular mycorrhizal fungi (AMF). Lower shoot δ(18)O but unchanged δ(13)C values in plants from the NT system suggest enhanced stomatal conductance but also enhanced photosynthetic rate, which overall resulted in unchanged water use efficiency. Bean plants in the NT system showed lower shoot δ(15)N values, which suggests that a larger proportion of total plant nitrogen was obtained through atmospheric nitrogen fixation in this treatment. CONCLUSION: Greater diversity of AMF soil communities and heavier colonisation of roots by AMF in the NT compared with the MP system appeared to contribute to improved crop nutrition, water relations and yield in this rain-fed agroecosystem.
Subject(s)
Agriculture/methods , Isotopes/metabolism , Mycorrhizae , Nitrogen/metabolism , Oxygen/metabolism , Phaseolus/physiology , Phosphorus/metabolism , Biomass , Carbon/metabolism , Conservation of Natural Resources , Crops, Agricultural/microbiology , Crops, Agricultural/physiology , Mexico , Nitrogen Fixation , Phaseolus/microbiology , Photosynthesis , Plant Structures/metabolism , Plant Structures/microbiology , Rain , Soil Microbiology , Water/physiologyABSTRACT
Se reportan 124 casos de pilomatricoma diagnosticados en el HGZ Núm. 14 del Instituto Mexicano del Seguro Social (IMSS)-Guadalajara, en el periodo comprendido de 1986 a 1995. El tumor afectó principalmente a niños y adultos jóvenes y su prevalencia fue de 3.26 casos por 100,000 derechohabientes. Se hace una revisión del tema y se mencionan los principales hallazgos histopatológicos del tumor