TABLE 1.—Metabolites leached from plant foliage (Tukey 1966) 
Organic 
Inorganic Carbohydrates Amino acids Organic acids 
Boron Fructose Alanine Aconitic 
Calcium Galactans Arginine Adipic 
Chlorine Glucose Asparagine Ascorbic 
Copper Lactose Aspartic Citric 
Iron Pectic substances B-alanine Fumariec 
Magnesium Raffinose Cysteine Glutaric 
Nitrogen Sucrose y-aminobutyric Glycolic 
Phosphorus Sugar alcohols Glutamine Lactic 
Potassium Glycine Maleic 
Silica compounds Histidine Malic 
Sodium Hydroxyproline Malonic 
Strontium Isoleucine Pyruvic 
Sulfur Leucine Succinie 
Zine Lysine Tartaric 
Methionine Acidic glycosides 
Phenylalanine 
Proline 
Serine 
Threonine 
Tryptophan 
Tyrosine 
Valine 
they are in contact with leaching solutions 
(Tukey and Morgan 1963). Therefore, leach- 
ing might be more pronounced from grazed 
plants than from ungrazed plants. Frosts fol- 
lowed by rain also might increase leaching 
losses and thus reduce the nutritive value of 
range plants. 
Intensity and volume of rain affect degree of 
leaching. A light drizzle over a long period re- 
moves considerably more nutrients than an in- 
tense storm does. Dew is an effective leaching 
agent, especially in seasons and climates where 
rainfall is low. Other factors that influence 
leaching are light, temperature, and the nutri- 
tional status of the plant. 
Temperature 
Temperature is important in determining 
rate of development, phenology, and total yield 
of many plants, thus indirectly influencing 
chemical composition. However, effects of tem- 
perature are often confounded with effects of 
rainfall and other influences. It is clear that 
high temperatures are generally detrimental to 
plant growth, but distinguishing response to 
temperature from response to a moisture defi- 
ciency caused by the high temperature is diffi- 
cult (Laude 1964). 
In herbaceous plants in active growth or in 
the flowering stage, an increase in air or soil 
temperature up to 80°F. often increases the ni- 
trogen (protein) content in the foliage. In 
growth chamber studies, Brown (1939) and 
Bowman and Law (1964) determined that the 
percentage of protein of grasses increased as 
(a) 
60 
temperatures increased from 60° or 65° to 
80°F. Similar increases in percentages of ni- 
trogen in the foliage of various plants, caused 
by increases in soil temperatures up to 80°F., 
were reported by Nielsen et al. (1960a, 1960b). 
These increases may have been at least partly 
related to morphological changes in plants. In 
some studies grasses were reported to have a 
higher leaf-to-stem ratio at higher tempera- 
tures. Leaves of grasses usually contain more 
protein than stems (Cook et al. 1959); thus, 
more leafy plants would be expected to have 
higher protein content. 
Increases in percentage of phosphorus in fo- 
liage with increased soil temperature were re- 
ported by Nielsen et al. (1960b, 1961) and Lev- 
esque and Ketcheson (1963). However, in- 
creased temperature does not cause increases 
in nitrogen and phosphorus in all species. Niel- 
sen and Cunningham (1964) found that the 
content of these nutrients in Italian ryegrass 
was little affected by temperature. 
The response of other nutrients to tempera- 
ture is quite variable. A decline in content of 
nitrogen-free extract with increasing tempera- 
ture was reported by Brown (1939), and de- 
clines in lignin and cellulose content with in- 
creasing temperatures were reported by Bow- 
man and Law (1964). Brown (1939) found ash 
content little affected by temperature. 
Mellin et al. (1962) found that protein con- 
tent and digestibility of timothy, which nor- 
mally decreased in June as plants approached 
maturity, increased somewhat after a week of 
low temperatures and above-normal rainfall. 
However, this change was probably due to in- 
