Photosynthesis, trees

Trees and forests are susceptible to acid rain, too. Acid rain breaks down the protective waxy coating on leaves and interferes with photosynthesis. Tree growth is impaired as nutrients and minerals in the soil dissolve and wash away. In eastern Enrope, acid rain is causing an environmental disaster. Nearly 70% of the forests in the Czech Republic have been severely damaged, and some parts of the land are so acidic that crops will not grow. 

An extensive source of natural pollutants is the plants and trees of the earth. Even though these green plants play a large part in the conversion of carbon dioxide to oxygen through photosynthesis, they are still the major source of hydrocarbons on the planet. The familiar blue haze over forested areas is nearly all from the atmospheric reactions of the volatile organics... 

Damage to epicuticular waxes Altered photosynthesis Increased water loss Accumulation of acidic anions Leaching of ions, sugars, etc. Mineral imbalances Altered metabolism Increased susceptibility to winter freezing injury Death of fine roots Destabilization of trees Reduced water/mineral uptake Reduced water uptake Cations leached below roots Accumulation of acidic anions Altered structure/texture Altered microflora Reduced litter decomposition Altered N transformations Solubilization of metal ions... 

Fig. 1. (a) Schematic representation of the three types of anoxygenic ([1] and [2]) and oxygenic ([3]) photosynthesis found in plants and bacteria, (b) Phylogenetic tree based on 16S-rRNA sequence comparisons featuring only photo synthetic phyla. 

In certain plant habitats or niches, access to resources depends crucially upon rapid growth under conditions of climatic stress. Examples of this phenomenon are particularly obvious on shallow soils in continental climates where the growth window between winter cold and summer desiccation may be extremely short. In deciduous woodlands in the cool temperate zone an essentially similar niche arises in the period between snow melt and closure of the tree canopy. Both circumstances provide opportunities for high rates of photosynthesis and mineral nutrient capture in the late spring but depend upon rapid expansion of roots and shoots in the low-temperature conditions of the late winter and early spring. 

From an energy perspective, forests are bank accounts that store the results of photosynthesis. When we cut and bum wood, we make withdrawals from these energy accounts. So long as we do not cut more rapidly than trees can replace themselves, forests represent a renewable energy resource. In the past, as well as in some parts of the world today, forests were harvested much more rapidly than they reproduced. Fortunately, attitudes about forest use are changing, and modem forestry practices make it possible to sustain this energy resource. 

This the reverse of the process occurring in Equation 6.1, the decay of 14C, and results in a nearly constant concentration of 14C in the atmosphere. Any living organic synthesis on Earth, such as photosynthesis, will then capture the 14C and produce a 12C/14C ratio in living things to be fixed. When a tree is used for wood in an object such as a museum artefact then the 12C/14C ratio changes and the age of the sample can be calculated using Equation 6.5 as before. 

The two plants that seem to be the best bet for ridding one s home of such chemicals are ferns and palms. These plants release moisture as part of photosynthesis and, as they do, pull chemicals from the air into their leaves. Even NASA has conducted some greenhouse experiments for long-term space exploration. Within hours, their plants [palms] had removed almost all traces of formaldehyde in the room. Both species of plants are ancient, dating back more than a hundred million years. Another trait they share is that they both live long lives, 100 years or more. This we expect from trees, but ferns and palms are plants plants that can grow to 65 feet in the proper setting Even their individual leaves live for one to two years [ferns] and one to nine years [palms]. Perhaps it is their primal qualities that have contributed to their ability to purify their environment. 

Choinski, J.S. Jr. and Johnson, J.M., Changes in photosynthesis and water status of developing leaves of Brachystegia spiciformis Benth., Tree Physiol, 13, 17, 1993. 

As discussed in the answer to exercise 94, trees and other photosynthetic plants absorb atmospheric carbon dioxide in the summer, which causes a decrease in atmospheric CO, levels by the fall. During the winter, the plants lose their leaves and photosynthesis stops. The fall and winter decay of the organic matter generates carbon dioxide, which increases the atmospheric CO, levels by the spring. Most of the land mass of our planer is located in the northern hemisphere. Therefore, that s where most of the CO,-consuming photosynthesis from trees and plants takes place. 

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