Juan Ángel Larrinaga-Mayoral

Preliminary compositional nutrient diagnosis norms for cowpea (Vigna unguiculata (L.) Walp.) grown on desert calcareous soil

This study calculated the compositional nutrient diagnosis (CND) norms of cowpea (Vigna unguiculata (L.) Walp.), as well as identified significant nutrient interactions of this crop growing in an irrigated calcareous desert soil. Three genotypes were distributed in rows in a 2-ha field. The soil showed high heterogeneity in its chemical properties. For statistical analysis, 86 foliar composite samples from healthy plants were used. Preliminary CND norms were developed using a cumulative variance ratio function and the χ2 distribution function. Means and standard deviations of row-centered log ratios VX of five nutrients (N, P, K, Ca, and Mg) and a filling value R, which included all nutrients not chemically analyzed. Preliminary CND norms are: VN*=0.174±0.095, VP*=−2.172±0.234, VK*=−0.007±0.267, VCa*=−0.022±0.146, VMg*=−1.710±0.132, and VR5*=3.728±0.084. These CND norms are associated with dry bean yields higher than 1.88 t ha−1, and are associated with the following foliar concentrations: 26.2 g N kg−1, 2.5 g P kg−1, 22.9 g K kg−1, 21.6 g Ca kg−1, and 4 g Mg kg−1. Cowpea plants growing in desert calcareous soils took up lower amounts of N, P, and K than those considered as optimum in a previous report. Six interactions were strongly indicated for cowpea through principal component analyses: positive for Ca–Mg, and negative for N–Ca, N–Mg, Ca–P, Mg–P, and K–P. Furthermore, two interactions were identified using simple correlations, negative N–P and positive K–Ca.

Differential responses of Jatropha species on growth and physiological parameters to salinity stress at seedling plant stage.

The effect of salinity on Jatropha curcas (J. curcas), native to nonsaline humid areas, and Jatropha cinerea (J. cinerea), native to saline dry areas, was compared to assess the potential of cultivating J. curcas for biodiesel production in saline soils that are not suitable for food production. Growth parameters, water relations, chlorophyll content, and stomatal conductance of both species under salinity were measured. Dry weight of both species decreased with increasing concentrations of salt; however, both species can grow at salinities up to ˜100 mM sodium chloride (NaCl). Decline of stomatal conductance was one of the main factors causing reduction in growth of Jatropha spp. Growth of J. curcas was inhibited more than that of J. cinerea by decline in growth parameters and chlorophyll content, but J. curcas shows sufficient hardiness to be cultivated in moderately saline soils with more favorable water relations.

Differential responses of Chiltepin (Capsicum annuum var. glabriusculum) and Poblano (Capsicum annuum var. annuum) hot peppers to salinity at the plantlet stage

Poblano (Capsicum annuum var. annuum) and Chiltepin pepper (Capsicum annuum var. glabriusculum) are considered closely related parent species. Poblano pepper is a cultivated species that has lost stress tolerance attributes, and Chiltepin is a wild species adapted to adverse environmental conditions, such as salinity stress. Differential physiological responses between the wild and cultivated species were compared in order to study the physiological and biochemical mechanisms of Chiltepin’s salinity tolerance. Salt stress treatments were applied to Chiltepin and Poblano and their growth, chlorophyll content, transpiration rate, and concentrations of anions and cations in leaves, stem and roots were measured. Dry weight and relative growth index decreased significantly with salt stress in Poblano, chlorophyll-a decreased significantly in both peppers and transpiration decreased in Chiltepin, with no significant changes evidenced by Poblano. Concentrations of Na