The next time you sip a margarita or a tequila sunrise, pause for a moment to reflect on the contribution made to the tequila industry by some long unacknowledged friends: long-nosed bats. These bats (Genus Leptonycteris) are the main pollinators of Century Plants (Agave sp.), and the tequila is obtained through distillation of juices from agaves. The relationship between bats and tequila may seem obscure at first, but the bat-plant association is so strong that the disappearance of one would threaten the survival of the other. Recent surveys have shown that populations of long-nosed bats could be declining, but the possible impact on plants or the tequila industry has not been determined. The tequila connection has three main actors: the bats, the plants, and man.
Nectar and pollen are the main food items for long-nosed bats. Some plants, such as the Saguaro and Organ Pipe cacti, some species of agaves, and a variety of tropical species, open their flowers at night and attract bats with copious amounts of nectar. As bats feast on this sweet repast, their fur gets coated with pollen grains. When they fly to another plant in search of more food, they transfer the pollen to a new flower, assisting in cross-fertilization of the plants. Both the plant and the bat benefit from this relationship, and therefore are said to be mutualists. Scientists believe that this association is the result of the coevolution of bats and plants and that the dependence is so strong that the plants could not reproduce without the intervention of the bats, which would starve to death if the plants were not present. This relationship seemingly is quite sensitive to disturbance.
Just how could crucial be employed to find plants
Unfortunately, it is not often easy to assess the causes of vulnerability of certain species, especially for secretive animals like bats. Habitat destruction is likely the major factor affecting long-nosed bats. They are specialized nectar feeders and disappearance of their food plants could explain the decline in their populations. The fragility of the mutualistic relationships is magnified in the case of the long-nosed bats because of their migratory habits. These bats depend not only on the plants in a given region, but on a continuous supply of food along their migratory routes. Pesticides frequently are cited as a major threat to bats, but they are unlikely to seriously threaten nectar-feeding species. A possibility that has not been evaluated is that local cattlemen, in a misguided attempt to control numbers of vampire bats in Mexico, have destroyed colonies of cave-dwelling bats indiscriminately. South of the U. S. border, long-nosed bats and vampires frequently share the same caves.
The decline in populations of Leptonycteris could have terrible consequences. Many plants that depend on the long-nosed bats for their reproductive success are important components of their communities, providing food and shelter for a variety of other animals. Bees, moths, lizards, hummingbirds, woodpeckers, orioles, finches, sparrows and field mice all depend on plants pollinated by long-nosed bats, and they would be affected indirectly by reduction in bat numbers because of the concomitant decrease in plant populations. In this sense, long-nosed bats are keystone mutualists, being part of a web of ecological interactions that would be disrupted seriously by the disappearance of the bats. Furthermore, because of their migratory habits, Leptonycteris are also mobile links, connecting habitats that otherwise would lack interchange. The destruction of certain habitat in Arizona could have severe effects, through the bats, on the plant communities in Mexico. Indiscriminate killing of bats by cattlemen in Mexico potentially could affect the future of agave populations in Texas. We are facing the problem of a keystone species that moves across international borders, creating special complications that will be solved only through collaborative work of Mexican and American specialists.
Since the first prehistoric Indian discovered how to use magueyes, bats of the genus Leptonycteris have played a silent, unacknowledged role. The ancestral Mexicans did not realize that the reproduction of the indispensable magueyes depended on pollination by a secretive, nocturnal ally. Today, most of the agaves employed in the production of pulque, mezcal, and tequila are cultivated and vegetatively propagated, and the species used in the fiber industry is a hybrid that is also vegetatively propagated. However, wild populations of "maguey pulqero" (A. salmiana), as well as of A. angustifolia and A. tequilana, still exist. In fact, part of the mezcal and pulque production comes from these uncultivated stocks. These wild populations depend on the bats for their conservation, but no research has been done to demonstrate the extent of this dependence. The possible impact of the extinction of wild stocks on beverage production has not been evaluated. Wild populations are the only source of new varieties of plants propagated vegatatively, so conservation of wild agaves (and consequently of bats) should be an important issue for any industry that exploits cultivated lineages.
The future Man has depended upon agaves for centuries, but only recently have we realized that bats are also partners in this alliance. Long-nosed bats are endangered by modern man's activities, and although we do not know exactly how the extinction of these bats might affect the industries that depend on agaves, one thing is sure: the effect will not be positive. From this point of view, it makes clear economic sense to protect bats of the genus Leptonycteris. Economic reasons are not, however, the only motives for protecting an animal species. Long-nosed bats and agaves are the products of thousands of years of coevolution and have developed special adaptations for living together. From an ethical point of view, man has no right to terminate an association that began several centuries before civilization. Finally, from an aesthetic point of view, it would be disturbing indeed to destroy the delicacy of the fragile links that connect long-nosed bats, agaves, and the diverse assemblage of animals that find food or shelter on these plants.
Plants are an abundant source of potential new medicines and often serve as chemical templates for the design of novel drugs to treat humanity's most serious ailments. We're finding new candidate plants all the time. Researchers then spend months and years isolating their active ingredients and reproducing them in a lab.
At the time, the drug was taken orally (whereas today it is usually administered intravenously) and Serturner experimented on both himself and his volunteers to find a safe dose. Like opium, many of the plants we use to treat illnesses are toxic and must be taken in carefully measured non-lethal doses.
Tobacco plants are easy to alter and manipulate due to their genetic makeup, so they are perfect candidates for testing new technologies. Biologists in Oklahoma are developing plants with seeds containing proteins that thin the blood, helping to fight stroke and heart disease. And as tobacco is an inexpensive, high-volume crop that's already grown worldwide, this could be a sustainable and low-cost way to produce new complex medicines.
Plant growth and development largely depend on the combination and concentration of mineral nutrients available in the soil. Plants often face significant challenges in obtaining an adequate supply of these nutrients to meet the demands of basic cellular processes due to their relative immobility. A deficiency of any one of them may result in decreased plant productivity and/or fertility. Symptoms of nutrient deficiency may include stunted growth, death of plant tissue, or yellowing of the leaves caused by a reduced production of chlorophyll, a pigment needed for photosynthesis. Nutrient deficiency can have a significant impact on agriculture, resulting in reduced crop yield or reduced plant quality. Nutrient deficiency can also lead to reduced overall biodiversity since plants serve as the producers that support most food webs.Changes in the climate and atmosphere can have serious effects on plants, including changes in the availability of certain nutrients. In a world of continual global climate change, it is important to understand the strategies that plants have evolved to allow them to cope with some of these obstacles.Two classes of nutrients are considered essential for plants: macronutrients and micronutrients. Macronutrients are the building blocks of crucial cellular components like proteins and nucleic acids; as the name suggests, they are required in large quantities. Nitrogen, phosphorus, magnesium, and potassium are some of the most important macronutrients. Carbon, hydrogen, and oxygen are also considered macronutrients as they are required in large quantities to build the larger organic molecules of the cell; however, they represent the non-mineral class of macronutrients. Micronutrients, including iron, zinc, manganese, and copper, are required in very small amounts. Micronutrients are often required as cofactors for enzyme activity.Mineral nutrients are usually obtained from the soil through plant roots, but many factors can affect the efficiency of nutrient acquisition. First, the chemistry and composition of certain soils can make it harder for plants to absorb nutrients. The nutrients may not be available in certain soils, or may be present in forms that the plants cannot use. Soil properties like water content, pH, and compaction may exacerbate these problems.Second, some plants possess mechanisms or structural features that provide advantages when growing in certain types of nutrient limited soils. In fact, most plants have evolved nutrient uptake mechanisms that are adapted to their native soils and are initiated in an attempt to overcome nutrient limitations. One of the most universal adaptations to nutrient-limited soils is a change in root structure that may increase the overall surface area of the root to increase nutrient acquisition or may increase elongation of the root system to access new nutrient sources. These changes can lead to an increase in the allocation of resources to overall root growth, thus resulting in greater root to shoot ratios in nutrient-limited plants (Lopez-Bucio et al., 2003).Plants are known to show different responses to different specific nutrient deficiencies and the responses can vary between species. As shown in Figure 1, the most common changes are inhibition of primary root growth (often associated with P deficiency), increase in lateral root growth and density (often associated with N, P, Fe, and S deficiency) and increase in root hair growth and density (often associated with P and Fe deficiency). 2ff7e9595c
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