
- •Introductory
- •3. Agriculture and the industries. ВЂ” Agriculture is at
- •Introductory 3
- •Introductory * 5
- •Inous substance develops on the outside of the cell-wall
- •30 The Principles of Agronomy
- •Ings around the stopper and plant be sealed to prevent
- •200 Pounds of water
- •Interaction of the elements.
- •Ing herds ; cats and birds in the control of mice and in-
- •It shall be for meat" (Genesis I. 28, 29).
- •82. How to modify structure. ВЂ” The structure of a
- •98. Need for preventing evaporation. ВЂ” The plant
- •122. Composition of soils. ВЂ” Soils are made up largely
- •133. How to determine fertilizer needs. ВЂ” In the
- •Is completed by bacteria. The carbon of the organic
- •162. Reasons for rotation of crops. ВЂ” Some sort of
- •152 The Principles of Agronomy
- •Influence the amount of erosion that will take place.
- •169. Methods of preventing erosion. ВЂ” Erosion cannot
- •180. The kernel, dry and fairly smooth, has a deep
- •174 The Principles of Agronomy
- •It grows on sands, loams, clays, and silts, avoiding the
- •184. Seed and seeding. ВЂ” Farmers had better use
- •In wheat. High nitrogen and low moisture content in
- •197. Prices vary a few cents according to grade. In
- •If a man buys a million bushels and holds it for a time,
- •221. Uses and value. ВЂ” About nine-tenths of the
- •224. Description. ВЂ” The oat plant has a fibrous root-
- •226. Distribution. ВЂ” Oats are naturally adapted to
- •Is not so good seed as a smaller one from a good hill. It
- •250. Cutting and planting. ВЂ” How large to cut the
- •266. Manufacture of sugar. ВЂ” When the factory is
- •279. Flowers and seed. ВЂ” At blossoming time, each
- •In liberal quantities, as it is likely to be where no leaching
- •270 The Principles of Agronomy
- •297. Crimson clover (Trifolium incarnatum), much
- •311. Description. ВЂ” Timothy bears a slender, spike-
- •327. Value and use. ВЂ” Orchard-grass yields about as
- •Various crops so selected, planted, and arranged as to
- •In other groups. The stalks are fine and leaves more
- •366. Distribution and adaptation. ВЂ” As might be
- •Vators, good harrows, and efficient plows have been in-
- •373. Harvesting and marketing. ВЂ” As soon as the bolls
- •380. Miscellaneous fibers. ВЂ” Manila hemp, or abaca
- •389. Sweet potatoes. ВЂ” Most of the sweet potato
- •401. Artificial selection. ВЂ” Because man has put his
- •390 The Principles of Agronomy
- •430. Work in producing various crops. ВЂ” In arranging
- •Very simple. During the last century, however, there
- •434. Machines that are seldom used. ВЂ” Some pieces
- •444. Keeping records. ВЂ” The fanner cannot, without
- •406 The Principles of Agronomy
- •621. Marketing Farm Products.
- •430 Appendix
- •Is the anther or pollen-case, and this is usually borne on a stalk
- •Ing and marketing the product. It treats in detail some eighteen individ-
200 Pounds of water
have passed through
the plant. Measure-
ments of transpiration
show that about 300
pounds of water are A^
required for one pound ^9^
of growth in corn and Vat
about 500 pounds for F'"- H— Comparison of water used with
, , ,, . wheat produced. (After Widtsoe.)
one pound of growth m
wheat (Fig. 14). A pint of wheat weighs a pound, but 60
gallons of water are necessary to produce it. If the straw
weighs as much as the grain, three 40-gallon barrels full of
water are transpired in growing the pint of wheat. This
quantity of water used in growing a pound of dry substance
is called the water-cost of dry matter for the particular plant.
48 The Principles of Agronomy
Crops growing in hot, sunshiny regions transpire more
water than in humid regions. Dry air, winds, poor soil,
weak plants, and an abundance of water in the soil cause
more water to be used for dry matter produced. Desert
plants and drouth-resistant crops have the power to hold
so much water in their tissues against the forces of tran-
spiration that they do not die from wilting. Some plants
also have the power of developing few or many stomata
according to whether they have small or large quantities
of water at their disposal. Some plants transpire much
more water than others ; most plants seem to be wasteful
during the period of bloom ; and quick-growing crops use
more water than steady-growing ones. Darkness also
diminishes transpiration considerably.
35. Translocation. — Since all the starch and other
plant-food is elaborated in the leaves, this must be moved
or the leaves would be the largest part of the plant. En-
zymes change sugar into starch for storage, and then to
sugar again when moving is begim. The solubility of
sugar allows the sap stream to carrj^ it to the fruit, stem,
or root for use or for storage. For example, great quan-
tities of sugar or starch are stored in roots of carrots to
be moved to the flowers and seed when the plant matures
and* seed is set. Fruit trees move food from wood to the
fruit. Seed and fruit often grow so rapidly that storage
in early summer is necessary. This movement of elabo-
rated food from one part of the plant to another is called
translocation. Most crop plants become more or less
porous in stem or roots, or in both, during the seed-setting
period owing to the transfer of food material.
36. Transportation. — Water is transported upward
through the tracheal tubes and sap, downward through
the sieve tubes, or radially along medullary rays. Sap
can flow down largely by gravity and radially by capil-
Plant Functions 49
larity, or wick action. Both these forces aid osmotic
pressure in forcing the water upward. Whatever factors
are at work, the water seems to have little more trouble
in reaching leaves on a tree-top 200 feet above ground
than those on a strawberry plant.
A geranium-cutting with the cut end immersed in
red ink will soon show red stains moving upward. They
will finally extend along the leaf-veins causing red blotches
in the leaves where the liquid is released into the spaces
between the cells. A plant stem several inches in length
will be traversed in a few minutes. The rate of movement
varies from a few inches to several feet an hour.
37. Response. — Nearly all plants tend to grow verti-
cally, even on a steep hillside where it would seem that
growth at right angles to the slope would afford the
firmest root attachment. Most plants in windows lean
toward the light, and must be turned every few days
to prevent their becoming one-sided. Roots, in wet soils,
nearly always grow in the surface layer, while on dry,
well-drained soils, they penetrate deeply. It is coimted
a good practice to withhold irrigation water as long as
possible in order to promote deep rooting. Oxygen as well
as water limits the growth in swamped soils. Many
plants do not thrive save on soils rich in lime. Alfalfa
is a notable example.
SUPPLEMENTARY READING
Any textbook of botany.
Plant Physiology, B. M. Duggar.
Plant Physiology, L. Jost.
Plant Physiology, G. J. Peirce.
Cyclopedia of American Agriculture, Vol. II, pp. 11-22.
B
CHAPTER V
THE PLANT AS A FACTORY
Notwithstanding their complexity, plants are simple
in their purpose if they can be said to have such. All their
energies are bent toward seed production or toward some
other means of continuing the species, that is, of transmit-
ting life and characteristics to another generation. Sin-
gleness of aim seems to show the organization of the plant
and the variety of ways in which it attempts to preserve
itself in the struggle for existence. Power to gather
raw foods and elaborate them into tissue-building com-
pounds, storage of these products in some part of the
plant against the time of greater needs, and adjustment
to surroundings are nothing more than manifestations
of the struggle to perpetuate the species.
In the products of the plant, man is vitally interested.
Sometimes it is the roots, sometimes the stem, the seed,
or the fruit containing stored starch, sugar, oil, or pro-
tein that draws his energy in producing and harvesting.
Often it is just the dead cell-walls, such as wood, cork, or
straw ; but other times he takes the plant in the midst
of life to get immature steins for forage, sap for rubber or
turpentine, or cell-contents for sugar. Every part of the
plant has been put to use ; roots, stems, leaves, flowers,
seeds, and sap, all furnish useful products. For example,
beets and carrots are roots, hay is both stem and leaf,
grain and beans are seeds, some perfumery is made of
blossoms, and cane-sugar is a sap product. Drugs and
50
The Plant as a Factory 51
stimulants, such as opium, tobacco, and quinine, come
from substances known as alkaloids that may be found in
any part.
38. Interdependence of plants and animals. — If only
plants were upon the earth, then the provision of nature
for plants to give up oxygen and use carbon dioxide and
for animals to reverse these processes, would be useless.
Animals feed upon plants, directly and indirectly ; directly
when they are plant-eaters, and indirectly when tliey are
flesh-eaters; for the prey of carnivorous animals either
ate plants, or animals that ate plants. On the other
hand, decayed bones, flesh, and manure restore to the
sofl and air substances upon which the plants feed either
directly or indirectly ; directly when plant-food is at once
taken from the broken-down tissues, and indirectly when
these decaying substances promote the growth of soil bac-
teria which take atmospheric nitrogen and make compounds
that the plant absorbs. Soil devoid of organic matter —
decaying plant and animal substance — is almost useless
on account of its being compact. It can hold water
for only a short time ; air and heat cannot pass through
it readily.
Many plants require limestone soils for development.
Part of the limestone ledges supplying lime is composed
largely of shells of small animals that extracted lime from
the water in which they lived. These animals probably
fed on water plants, and breathed oxygen released as
by plant processes. In the economy of nature, plants
and animals need each other.
39. Dependence of man on plants. — Since animals
depend on plants for their food, man, who in turn depends
on plants and animals, may be regarded as being ulti-
mately dependent on plants. It is not difficult to see
that almost all hiunan food, save only a few minerals
52 The Principles of Agronomy
such as salt, comes entirely as a result of life processes.
Milk, cheese, butter, flesh, and eggs are body products
of animals ; bread, fruit, vegetables, and " greens "
are plant contributions. Furthermore, they are produced
almost entirely by domesticated plants and animals.
Clothing, likewise, comes largely from the same sources.
Cloth made from wool, hair, cotton, or flax fiber is just
as truly the product of animals and plants as are the skin
garments of the Eskimo or the leaf and bark raiment of
the tropical savage; furs, gloves, shoes, and straw hats
are made directly from products of the life processes.
Formerly, most dwelling places were built of wood and
leaves or of skins. Modern buildings consist largely of
brick, stone, concrete, and metal, but wood is used in
lathing, for floors, door and window frames, for roofing, and
for walls in many cases. Furniture and useful tools will
for years to come, if not always, be composed largely of
wood. Attention to forestry indicates that man realizes
this and is making an effort to preserve his timber re-
sources. Moreover, far back in the history of cement,
brick-clay, some rock, and some metals, life has played
a part. Especially is this true wherever carbonate com-
pounds exist, since others as well as limestone have re-
sulted from an organic process somewhere in the chain of