Thermal buffering capacity of the germination phenotype across the environmental envelope of the Cactaceae.

Recruitment from seeds is among the most vulnerable stage for plants as global temperatures change. While germination is the means by which the vast majority of the world's flora regenerate naturally, a framework for accurately predicting which species are at greatest risk of germination failure during environmental perturbation is lacking. Taking a physiological approach, we assess how one family, the Cactaceae, may respond to global temperature change based on the thermal buffering capacity of the germination phenotype. We selected 55 cactus species from the Americas, all geo-referenced seed collections, reflecting the broad environmental envelope of the family across 70° of latitude and 3700 m of altitude. We then generated empirical data of the thermal germination response from which we estimated the minimum (Tb ), optimum (To ) and ceiling (Tc ) temperature for germination and the thermal time (θ50 ) for each species based on the linearity of germination rate with temperature. Species with the highest Tb and lowest Tc germinated fastest, and the interspecific sensitivity of the germination rate to temperature, as assessed through θ50 , varied tenfold. A left-skewed asymmetry in the germination rate with temperature was relatively common but the unimodal pattern typical of crop species failed for nearly half of the species due to insensitivity to temperature change at To . For 32 fully characterized species, seed thermal parameters correlated strongly with the mean temperature of the wettest quarter of the seed collection sites. By projecting the mean temperature of the wettest quarter under two climate change scenarios, we predict under the least conservative scenario (+3.7°C) that 25% of cactus species will have reduced germination performance, whilst the remainder will have an efficiency gain, by the end of the 21st century.

Producción de celulasas por hongos: estudios cinéticos en hongos silvestres / Production of cellulase by fungi: kinetic studies on wild fungi

The kinetics of cellulase production of six fungal production of six fungal strain isolated from soils of the Lomas de Lachay (Lima), was studiend and compared with that of the hypercellulolytic mutan T. reesei QM-9414. Submerget batch conditions and lactose (1%) as inducer were used. Increment velocities of enzyme activity were comparable with those of the mutant and a significant correlation between the highest endoglucanase activity and the diameter of hydrolisis on swollen cellulose plates was found. Likewise, all fungal strains overcame the mutant in specific activity (fivefold), productivity (twofold), and B-glucosidase titer (threefold9).

Seis diferentes hongos aislados de las Lomas de Lachay (Lima, Perú) fueron estudiados en su cinética de producción de celulosas y comparados con el mutante hipercelulotítico T. reesei QM-9414. Trabajando en cultivo sumergido utilizando lactosa al 1% como inductor, se detecto velocidades de incremento de la actividad enzimatica entre otros.