Plants of Agave spp. perform Crassulacean acid metabolism (CAM) and are highly drought-tolerant, but little is known concerning seed germination under low water availability. The aim of this study was to assess the effect of substrate water potential (ΨW) on seed germination and contrast hydrotime parameters of seven valuable and commercially-important Agave species from different geographical distributions and climatic regions of Mexico. Our hypothesis was that seed germination of Agave species is not affected by low water availability independently of seed biomass and the climate of their distribution area. Seed germination (at 25°C and in the dark) between 85 and 100% for all species occurred within 80–180 h at -0.03 MPa and 250–430 h at -1.0 MPa. Seed germination at -1.5 MPa declined to less than 50% (p < 0.05) for A. asperrima and A. cupreata but did not change significantly for A. americana var. marginata, A. lechuguilla and A. striata, although they showed the lowest mean base water potential (-2.01 to -2.64 MPa). Seed germination of 40% Agave species, from arid and semi-arid climates in this study, was not affected by the lower ΨW. Germination of seeds of Agave species is moderately affected by low water availability, is partially dependent of their ecological distribution, and is independent of seed mass.

Warmer temperatures predicted as a result of climate change will have an impact on milpa. An experiment was carried out with induced passive heat with the objective of simulating the increase in temperature on the physiological, morphological, and yield parameters of milpa from different climates of San Luis Potosí, Mexico. Two different environments, Open-top chambers (OTC) and control, and three milpas, from warm–dry, temperate, and hot and humid climates, were studied. A total of 12 experimental units of 13.13 m² were used in the random design, with a factorial arrangement of 2 × 3 and two replications. Abiotic variables (minimum, maximum, and mean daily temperatures and accumulated heat units) were determined and compared between the two environments and confirmed that the OTC increased the abiotic variables. The growth and development parameters increased under the warming effect. Furthermore, the milpa from hot and humid climate was the least affected. In contrast, the warming considerably delayed yield parameters. The squash suffered the most, while the bean benefited the most. The warming affected the chlorophyll fluorescence and gas exchange differently for each crop. However, at an early stage, the maximum photochemical efficiency (Fv/Fm) and non-photochemical quenching (qN) for bean and maize were reduced, while at a late stage, they were Fv/Fm, photochemical quenching (qP), and qN for maize; stomatal conductance and transpiration rate of the squash were improved under the warming treatments. In conclusion, the warming delayed the yield and photosynthetic parameters, while growth and development benefited. The milpa systems were differently affected by warming.

The present study aimed to evaluate the effect of copra meal (the waste coconut of the oil industry) on in vitro ruminal kinetic and greenhouse gases production and on in vivo lamb performance. Twenty-eight male Rambouillet sheep (initial body weight 24.5 ± 3.9 kg) were randomly assigned to one of the four treatments: 0, 50, 100, and 150 g of copra meal/kg in their diet (dry matter basis). Final weight, weight gain, and feed intake were not affected (p > 0.05) by the copra meal addition. The gas production volume (V) decreased, and the gas production rate increased, in a linear trend (p < 0.05) as copra meal was added to the diet. In contrast, methane and CO₂ production showed an opposite quadratic trend (p < 0.05), with the highest and lowest values reported at 100 g/kg DM of copra meal, respectively. The addition of copra meal in the lambs’ diet decreases the volume of gas production and is a strategy to decrease methane and carbon dioxide production in feeding without affecting animal performance.