Like humans and other animals, plants need sufficient nutrients to function and to grow. If the plant is deprived of these nutrients, it is unable to go through the chemical processes related to its survival and growth. Cigarettes contain more than 4,000 different chemicals, including arsenic (used as rat poison), butane (lighter fluid) and formaldehyde (fluid used in embalming). Some of these chemicals actually may benefit the plant. Carbon monoxide, for example, is able to be converted by the plant into carbon dioxide, which the plant can use readily for photosynthesis.
In general, however, most chemicals released during smoking contaminate the soil and air surrounding the plant to such a degree over time that the plant eventually cannot absorb sufficient amounts of the nutrients needed to sustain itself and to grow.
Plants are aided in growth by various microorganisms. Scientists believe these microorganisms produce enzymes and hormones that encourage plant growth. The chemicals found in cigarettes and cigarette smoke can harm or kill these microorganisms. If these microorganisms are reduced in number or are killed off altogether, the plant will not receive the enzymes and hormones that the microorganisms produce and thus won't be able to grow as well. It is much like depriving a person of a vitamin pill.
Respiration and Photosynthesis
Plants contain openings called stomata, which are part of the plant's respiratory system. These openings are at least partially responsible for the plant's absorption of CO2 and subsequent conversion into the glucose that the plant uses as food. Smoking can leave a residue on plants that effectively plugs up these stomata, which essentially causes the plant to "choke" and to starve. Plant growth thus is slowed because the plant cannot get what it needs for photosynthesis to take place.
Like humans and other animals, plants cells are made up of proteins, enzymes and other components. Chemicals have an impact on the stability of these components, including the plant DNA. The chemicals can break down molecular bonds, for instance, or they can cause mutations in the genetic material. These breakdowns and changes mean that the plant cell cannot function as was originally intended, which can impact everything from water absorption to seed production. Repeated exposure to the chemicals in smoke thus may hinder plant growth and health on the molecular level.