Effects of environmental factors on anatomy and morphology of plants

Considering the lack of knowledge and data available on environmentally induced anatomical and morphological changes in plants we believe it is important to examine in detail a plant's responsiveness to factors in its environment. This research tested the hypothesis that environmental factors (light, water and nutrient levels) affect development of anatomical and morphological characters in plants. Specimens were placed in experimental treatments of low, medium or high levels of light, water, nitrogen, phosphorus or a combination of these factors for one year. Control plants received medium levels of all factors. Single variable experimental plants received medium levels of all factors except the experimental factor; for example "high light" treatment consisted of high light but medium levels of water, nitrogen and phosphorus. Plants in multiple variable treatments received high levels of light plus high, medium or low levels of water and either high or low levels of nitrogen or phosphorus. Very few treatments affected development of wood or non-wood characters in any species tested. In general, all wood characters and those non-wood characters associated with structural shape (cortex and pith cell number and size) appear to be very stable under the conditions tested. Tracheary element diameter, the wood character most often affected in single or multiple variable tests, was affected by few treatments in any species (2 of 8 treatments in Cereus peruvianus and Mammillaria erectacantha, 2 of 12 in Cleistocactus strausii, and 1 of 7 in Cereus tetracronas). However, when all species were considered, this character responded to a wide range of treatments and responded by either increasing or decreasing mean diameter. This response by a single character in multiple species to various factors suggests that wood morphogenesis can be affected by environment, but the degree of response may be mediated by other factors such as evolutionary history or growth habit. Morphological characters that responded significantly to treatments (shoot elongation) responded to both single and multiple variable treatments. Response to multiple variables was often more than the additive effects of either variable when tested singly. This "multiplier" effect was not seen in any wood or other structural character.