Q. My orchid quit blooming while I cared for a friends profusely blooming plant for a year. When the visiting orchid was gone, my plant started sending out shoots again. Is there any evidence that plants are competitive?
A. There is scientific evidence that plants can communicate chemically and that they do compete, said Marc Hachadourian, manager of the Nolen Greenhouses at the New York Botanical Garden. But he added that one orchid could not prevent another orchid from flowering.
Its not uncommon for a plant to take a year off, said Hachadourian, who supervises the gardens orchid collection, so without knowing the exact circumstances of these two plants, such as whether the visiting plant completely shaded the resident plant, its probably purely coincidental that the resident orchid didnt flower that year.
As for plants that do compete, he cited black walnuts. They stymie other shade plants in the immediate neighborhood through the process of allelopathy, the release of compounds that inhibit plant growth.
In the case of the black walnut tree, the effect is particularly noticeable because the tree produces a considerable amount of a nontoxic chemical called hydrojuglone. This compound, found in leaves, stems, fruit hulls, inner bark and roots, oxidizes in the presence of air or soil into juglone, which is highly toxic to surrounding trees, making them wither and die. Juglone is one of many allelochemicals used by trees and plants.
Is sweating good for you?
Q. Are there any health benefits associated with sweating more during a workout? If so, is there a difference if sweat is induced by heat versus aerobic exercise?
A. Theres this entrenched idea that its good to sweat things out, said Oliver Jay, an associate professor of exercise physiology and director of the Thermal Ergonomics Laboratory at the University of Ottawa in Canada; by extension, sweating heavily during exercise is somehow healthier than misting daintily.
But sweating, per se, provides no health benefits, Jay said, apart from preventing overheating. The benefits derive from the exercise itself, and the more intense, generally, the greater the health benefits.
Core temperature rises during prolonged and vigorous physical activity, though, and your body must shed that heat. It does so in large part by sweating. The more vigorously you exert yourself, the more internal heat you produce, and the more you must sweat. Such strenuous exercise improves health through many different physiological mechanisms. But perspiring, in and of itself, does not provide or amplify those effects, Jay said.
That situation does not change if you are sweating because of a hot environment. Sweat is sweat, he said.
As a rule of thumb, drink when you feel thirsty, so that sweating does not become actually unhealthy.