292 



GARDENERS' CHRONICLE 



The Source of Plant Food 



WILLARD N. CLUTE 



IT is a difticult matler to convince the averas^e individual 

 that phuits do not take their food out of the ground. 

 Everywhere he sees vegetation rooted in the soil and 

 naturally infers that this is the source of their nourish- 

 ment, iloreover, it is a matter of common knowledge that 

 plants absorb from the soil, for if water l>e withheld from 

 any plant for a sufficient time, it invariably withers and 

 dies. It is. of course, true that plants absorb water and 

 mineral matter from the earth, but these are not foods in 

 the generally accepted meaning of the word, though water 

 or the elements of which it is composed form part of all 

 food. Water must be combined with other elements be- 

 fore it becomes food, however. 



Ordinarily foods are classed as carbohydrates, fats or 

 oils, and proteins. Probably the commonest are the carbo- 

 hydrates, represented by such substances as sugar, starch, 

 wood or cellulose, and inulin. If the water is completely 

 driven out of any of these, as in the process of making 

 charcoal from wood, a black substance known as carbon 

 is left. This is derived by plants, not from the soil, but 

 from the air. This carbon exists in the air in very minute 

 quantities combined with oxygen in the form of carbon 

 dioxide. In ordinary air there are only about three parts 

 of this gas in ten thousand and yet from such minute quan- 

 tities, all the food in the world is built up. 



Xot only are the water and carbon dioxide the basic 

 material from which food is made, but plants are the only 

 organisms in existence that can tear the elements in these 

 substances apart and re-combine them in the form of food. 

 The plant world, therefore, carries the animal world with 

 it as a sort of pensioner on its bounty. If all the plants 

 should perish, the animals would soon follow them from 

 sheer inability to get food. 



The whole problem of animal and plant nutrition is 

 bound up with the problem of securing energy. A small 

 part of our food is used in growth and repair, but the 

 major part is used in securing' energy with which we move 

 in carrying out a vast number of activities. This energy 

 was stored origmally in the food by plants, and the best 

 that animals can do is to break down the food already 

 formed and use the energy. Plants alone are able to ac- 

 cumulate and fi.x new supplies of energy. 



All day long the sun showers down on the earth various 

 forms of energy. Heat, light, electrical and chemical 

 rays fall u[)on the plants, and the latter, by means of cer- 

 tain green bodies in the cells known as chloroplasts, stop 

 and use certain of these rays. The heat rays seem most 

 important m promoting or hastening various life processes 

 in the plants, and only the light rays are sources of 

 ener^. It is well known that ordinary daylight is made 

 up of at least seven colors and that these are sorted out in 

 various ways to give the color effects that we see. An 

 apple, for instance, looks red because it reflects the red 

 rays and absorbs the others. Plants are green, therefore, 

 not because they use green rays, but because they rellcct 

 ihem. The fact that plants are green is of no advantage 

 to them ; it simply indicates that in the green parts some 

 of the iiglit rays are Ijeing stopped. This explains the 

 almost univer.sal color of plants and the further fact that 

 all independent plants invariably seek the light. Plants 

 that are not green are unalile to make use of the light rays 

 and consequently are unable to secure energy from this 

 source and are obliged to depend upon food marie by other 

 organisms, just as animals do. 



In the plant the light rays are turned to a form of 

 energy, similar to, or identical with, electrical energy, and 



by means of this the carbon dioxide and water are com- 

 l)ined to form starches and sugars. In making this com- 

 bmation a certain amount of oxygen is left over and this 

 is generally given ol¥ to the air, which probably accounts 

 for the idea generally held that plants breathe out what 

 animals breathe in. In the process of respiration, com- 

 monly called breathing, plants behave exactly like animals, 

 taking in oxygen and giving out carbon dioxide. 



The reason the process of respiration in animals and 

 plants is confused is that in food making, jjlatits have a 

 second process, known as photosynthesis, which animals 

 do not have, and which is exactly the reverse of respira- 

 tion, in fact this is no other than the process of food- 

 making which we have been discussing. Photosynthesis, 

 however, is so much more active than res])iration in plants 

 that it usually masks respiration and thus contributes to 

 the idea that it is the only jjrocess. 



There are only about ten chemical elements required by 

 ])Iants and only three of these, are concerned in food mak- 

 ing and the storage and release of energy. Since these 

 three are found in the carbon dioxide of the air and the 

 soil water the farmer sometimes ex])resses it by saying 

 that his crops are made of wind and water. It is well 

 known, however, that sterile soils will not grow crops and 

 that fertilizers must be added to most soils in order that 

 plants will thrive. The fertilizers, of course, contain the 

 other elements that are absolutely necessary to the well- 

 being of the plants. Some of these are concerned in the 

 ripening of wood and fruit, others are necessary in form- 

 ing chlorophyll, still others neutralize acids, promote plant 

 processes or contribute to the building up of the living 

 substance or protoplasm. Put the securing of energy and 

 the locking it up until needed in the form of wood, coal, 

 oil and food, is .almost entirely a matter of wind, water and 

 sunlight. 



ORNAMENTAL FLOWERING TREES AND 

 SHRUBS 



{Continued from page 291) 

 broke off branches. The effect is the stronger in propor- 

 tion as we plant larger groups of one sort and thus, ac- 

 cording to the time of bloom, we can create changing 

 Springtime pictures at different points of large public 

 parks. l'"or this pur|iose (|uite ixirticularly there shoidd 

 be recommendetl the ornamental apples mentioned above, 

 which, with their croijs of fruit, give additional charm. 

 This is true of the rock s|irays also, and of the .Aronias, 

 who.-e Autuni)i;d splendor mrd<cs them all the more val- 

 uable. 



In small gardens we do nut require the effect of m;issing. 

 Here we can lend oiu-selves entirely to specimen jMants 

 and can bring (|ui(e close to us the many bloimiing tyi)es. 

 .\ place may lie found in even the smallest garelen for 

 the low growing Mains Sargcnti, Piuimx japonica. P. 

 Iininilis and P. triloba, Ainclanchicr xpicata. all Aronias, 

 Chccnomcles and Cotoncastcr hupchcnsis. In gardens of 

 medium size let us plant the double Howering Japanese 

 ornamental cherries, the wonderfully beautiful Malus 

 HaHiana Parkmanii, M. iociisis fl. />/., I\!. Sicholdi. M. 

 thcifcra. Cotoncastcr vinllillora calocarpa and yet many 

 others of the kinds mentioned, each one of which i^roduces 

 a lovely sight by itself. He who once begins to make 

 friends of all these forms will thereafter always more 

 zcalouslv strive to hel]> introduce them everywhere. — 

 F. I!. M 



