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Time, Plant Growth, Respiration, and Temperature
Bruce N. Smith, Lyneen C. Harris, V. Wallace McCarlie, Dorothy L. Stradling,
Tonya Thygerson, Jillian Walker, Richard S. Criddle, and Lee D. Hansen
Brigham Young University, Provo, Utah
1I. INTRODUCTION
The earth is very dynamic and has undergone dramatic changes in its history. All of the elements, in-
cluding those common in living things, were synthesized from primordial hydrogen in the interior of stars
[1]. Supernovas and other stellar instabilities dispersed many elements into space. Because hydrogen and
the noble gases are greatly depleted on earth as compared with their cosmic abundances [2], it is likely
that the chunks of matter giving rise to the protoplanet did not carry with them gaseous shells of their own.
As a result of contraction and redistribution of materials in the developing planet, a hydrosphere and at-
mosphere developed that were highly reduced [3]. The surface of the earth today is much more oxidized,
even to 21% O 2 in the atmosphere [4]. Was this oxidation linear or have there been fluctuations several
times during the history of the earth resulting in major species extinctions [5]?
Plants have evolved to survive, thrive, and grow by adapting to ever-changing conditions. The sea
was a stable, benign home for life during three fourths of the history of life on earth. Emergence on land
exposed living things to a much greater range of environmental conditions [4]. Increasing biological di-
versity to exploit new environmental opportunities has given us the present distribution of life on earth
[5]. Change continues today at an accelerated pace because of the impact of human activities. This chap-
ter explores ways in which adaptations to environmental changes have occurred and how plant
metabolism can be used to predict and better understand plant growth.
II. PLANT GROWTH
Plants grow by the process of cell division or mitosis followed by cell enlargement and maturation. Cells
then differentiate into tissues that make up the organs of the plant. Mitosis includes replication of or-
ganelles, synthesis of nuclear material, enzymes, etc. Cell enlargement consists largely of water uptake to
form a large vacuole. Growth may be measured as change in mass, volume, or length of shoot or root.
Crop productivity is often expressed not in biomass but in yield of the desired product: flower, fruit, seed,
root, oil, protein, or specific chemical.
Water, sunlight, carbon dioxide, oxygen, and mineral elements from the soil are well known to be
essential for sustained plant growth. If any of these things are deficient in the environment or present in
excess (toxic amounts), plants may become stressed and even die. But plants have adapted to life in a va-