Growing and Flowering in a Changing Climate: Effects of Higher Temperatures and Drought Stress on the Bee-Pollinated Species Impatiens glandulifera Royle

Drought and higher temperatures caused by climate change are common stress conditions affecting plant growth and development. The reproductive phase is particularly sensitive to stress, but plants also need to allocate their limited resources to produce floral traits and resources to attract pollinators. We investigated the physiological and floral consequences of abiotic stress during the flowering period of Impatiens glandulifera, a bee-pollinated species. Plants were exposed to three temperatures (21, 24, 27 °C) and two watering regimes (well-watered, water stress) for 3 weeks. Not all parameters measured responded in the same manner to drought and/or heat stress. Drought stress induced leaf senescence, decreasing leaf number by 15–30% depending on growth temperature. Drought also reduced photosynthetic output, while temperature rise affected stomatal conductance. The number of flowers produced dropped 40–90% in response to drought stress, while higher temperatures shortened flower life span. Both stresses affected floral traits, but flower resources diminished in response to higher temperatures, with lower nectar volume and pollen protein content. We conclude that increased temperatures and drought stress, which are becoming more frequent with climate change, can negatively affect flowering, even if plants deploy physiological resistance strategies.

Salicylic acid has allelopathy, but wheat and faba bean intercropping can alleviate faba bean fusarium wilt under salicylic acid stress.

BackgroundThe goals of this study were to evaluate the role of salicylic acid in the continuous cropping obstacle of faba bean (Vicia faba L.) and explore how intercropping with wheat alleviates these obstacles. We designed a hydroponic pot experiment to study the effects of exogenous salicylic acid on the occurrence of Fusarium wilt, seedling growth, physiological resistance of faba bean and pathogenicity of Fusarium oxysporum f. sp. fabae (FOF).ResultsThe results showed that salicylic acid significantly increased the incidence and disease index of faba bean, inhibited the growth of seedlings and reduced the physiological resistance of faba bean. An in vitro study of FOF found that salicylic acid increased the ability of the organism to produce fusaric acid, cellulase and pectinase, which increased the susceptibility of faba bean to Fusarium wilt. Interestingly, intercropping with wheat significantly reduced the exudation of salicylic acid from the faba bean root system, which directly reduced the deleterious effects of salicylic acid. Alternatively, intercropping also increased the ability of faba bean to defend itself from the aspect of physiological resistance and indirectly reduced the autotoxicity of salicylic acid.ConclusionsIn conclusion, we found that salicylic acid, as an autotoxic substance, deleteriously affected the growth of faba bean, but intercropping with wheat could alleviate its autotoxicity. This finding suggests the existence of an important mechanism in which intercropping alleviates the obstacles in continuous cropping and controls Fusarium wilt.

Integrating Concepts of Physiological and Behavioral Resistance to Parasites

Conceptual parallels between physiological and behavioral forms of resistance to parasites have led to the development of terminology like “the behavioral immune system” to refer to behaviors that combat parasites. I extend this metaphor by applying findings from research on physiological resistance to generate predictions for the ecology and evolution of behavioral resistance (here, synonymous with avoidance). In certain cases, behavioral resistance may follow similar evolutionary dynamics to physiological resistance. However, more research on the nature of the costs of behavioral resistance is needed, including how parasite transmission mode may be a key determinant of these costs. In addition, “acquiring” behavioral resistance may require specific mechanisms separate from classical forms of conditioning, due to constraints on timing of host learning processes and parasite incubation periods. Given existing literature, behavioral resistance to infectious disease seems more likely to be innate than acquired within the lifetime of an individual, raising new questions about how individual experience could shape anti-parasite behaviors. This review provides a framework for using existing literature on physiological resistance to generate predictions for behavioral resistance, and highlights several important directions for future research based on this comparison.

Spatio-temporal response mechanism of physiological characteristics of Abies georgei var. smithii to altitude

Abies georgei var. smithii (Abies George I varsmithorr. II (Viguie et Gaussen) Cheng et l.) belongs to Abies of Pinaceae, which is distributed in the southeast of Tibet, southwest of Sichuan and northwest of Yunnan. In this study, Abies georgei var. smithii in Sejila Mountain of southeastern Tibet was studied, the contents of Malondialdehyde (MDA), proline (pro), hydrogen peroxide (H2O2), soluble sugar and chlorophyll as well as the activities of superoxide dismutase (SOD) and superoxide dismutase (SOD) in the leaves, twigs, tree stems and roots of Abies georgei var. smithii were measured at different altitudes in the growing and non-growing seasons, single factor analysis of variance and multiple comparison were used to process the data. The results showed that the contents of Malondialdehyde (MDA), proline (pro) and hydrogen peroxide (H2O2) in the roots of Abies georgei var. smithii were significantly higher than those of other tissues in both growing and non-growing seasons, the content of chlorophyll in the leaves increased at first and then decreased with the elevation gradient, on the contrary, the ratio of chlorophyll a/b (CHLA/CHLB) increased with the elevation gradient. The activities of Peroxidase (POD) and superoxide dismutase (SOD) were the lowest. When the altitude was more than 4300m, the activities of POD and SOD decreased. The results showed that the physiological resistance of Abies georgei var. smithii decreased when the elevation was over 3900m, which was not beneficial to the growth and development of Abies georgei var. smithii, therefore, the distribution of Abies georgei var. smithii along the higher elevation gradient was limited by the unfavorable environmental factors at high altitude.

Evolution of behavioural resistance in host–pathogen systems

Behavioural resistance to parasites is widespread in animals, yet little is known about the evolutionary dynamics that have shaped these strategies. We show that theory developed for the evolution of physiological parasite resistance can only be applied to behavioural resistance under limited circumstances. We find that accounting explicitly for the behavioural processes, including the detectability of infected individuals, leads to novel dynamics that are strongly dependent on the nature of the costs and benefits of social interactions. As with physiological resistance, evolutionary dynamics of behavioural resistance can also lead to mixed strategies that balance these costs and benefits.

Allelopathy of Wheat and Faba Bean Extracts in an Intercropping System

Background We intensively studied faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) intercropping and found that this type of intercropping can effectively control the occurrence of faba bean wilt under field conditions. We conducted hydroponic experiments to explore the role of plant extracts in process of soil-borne diseases and the mechanism of disease control of faba bean and wheat intercropping. In this experiment, three concentration gradients of faba bean and wheat stems and leaves and root extracts were added to study the effects of faba bean and wheat extracts on faba bean growth, root physiological resistance and the growth of Fusarium oxysporum f. sp. fabae (FOF). Result Faba bean extracts significantly inhibited the growth of faba bean seedlings and the activity of root defense enzymes and significantly stimulated the growth of FOF at high concentrations. Compared with the treatment with faba bean extracts, wheat extracts significantly enhanced the growth of faba bean seedlings, increased the activity of defense enzymes and inhibited the growth of FOF. Conclusions Based on these results, we believe that wheat extract can effectively alleviate the autotoxicity of faba beans and also control the occurrence of faba bean wilt in the field. This provides a theoretical basis for practical intercropping to reduce the harm of faba bean wilt.