NUTRITION OF PLANTS.

Putaruru Press, Volume IV, Issue 160, 25 November 1926, Page 1

NUTRITION OF PLANTS.

WHAT THE ROOTS 80. Importance of Drainage. j A lecture on the roots of plants by Mr W. H. Jbace, Government orchard instructor, was uroadcasted from the Auciviaud station IYA recently. . “ When the culture of plants of trees is undertaken as a means of commercial gain or when it is desired that the greatest xiossible success shall leward the cultivator,” said Mr Rice, “it becomes very necessary to unders and the character of the individual plants one uses as a means of (or one might aimost say a machine of) production. “The fruit trees of to-day are propagated from selected trees by means of buds or grafts. That is known as vegetative reproduction and based on the fact that every individual bud is endowed with like characteristics to the plant on which it was grown. For the purpose under review the tree may be 'considered as it is received from the nursery. This will be found to consist of a root and stem. The root system will vary according to the soil conditions in which the plant has been grown. There may be many roots of a radiating habit or a strong root with a downward tendency, either system furnished with a liberal amount of root fibres. The roots directly eonnec cd with the base of the plant are termed primary roots—these do not remain singular, but give rise by division to side or secondary roots. Up to a certain pom: an abundance of plant food assists root action, but an excess retards root development as through it a fewer number of roots were able to provide the necessary amount of sustenance. The growing point of a root differs very much from the giowlng point of a stem; whereas the growing point of a stem is protected in a bud and well surrounded by rudimentary leaves, that of the root is to all appearances naked. This is not so, in fact, the extreme

point is well protected by a mass of cells, called the root-cap. With the friction of penetrating the soil many of these cells are killed while others die as the point of the root advances away from them. Structure and Functions. “A close examination of the root tip will show that the root cap extends back some li tie distance before the delicate root hairs arc found. These root hairs arc hollow t,ube-like formations outgrowth fvom the root surface, and for as long as they last arc concerned with the absorption of water and various soluble ingredients from the soil. These root hairs come into very close contact with the surface soil particles and are so delicate that a temporary excess of lack of water will destroy them. Though minute, these root hairs arc a very important part of the plant. Most of the plant food in its raw state is absorbed by them, and mainly by their aid is the plant kept well supplied with water, therefore any interference with their development subjects the plant to a severe check. While extending in length the root also increases in girth, giving a wedge-like formation ' which assists toward penetrating comparatively hard soils. The outer part of the root, corresponding to the bark on the stem, is composed of a single layer of cells thin-walled and easily jiciictratod by moisture. “Assuming that plant nutriments are present in the soil and recognising that the root formation is such that no solids can enter the plant, all materials to be of value to the plant must be rendered soluble in water, which is readily absorbed by the plant. As water is a primary necessity for plant development, it is absorbed very rapidly and in much larger quantities than remain in the plant. The process is such that large quantities are necessary to bring up tlie food- substances into

solubility. The excess of water is later given off by the leaves. Soil Management “The important plant foods contained in the soil must be rendered soluble in water before gaining entry to the plant tissues. This solubility is brought about in two ways, secretions by the plant istelf and bacteria. When the active parts of roots come into contact with suitable food a secretion is given off by the roots. This, plus the water, dissolves the substances, which are then a'osorbed by the cells. Only the roots in close contact with suitable material secrete this solvent, just as the animal gastric juices are stimulated by the presence of food. The action of bacteria is an important one and causes disintegration of vegetable matter, etc.

11 Root activity is of first importance, and a deep, well-drained soil provides the required conditions for roof development. Subsoiling or working to a great depth is not all that is necessary to make the soil deep. Depth suitable for root action depends a good deal on the water level in the land, and drainage is necessary to lower this water level in most soils. Many orchardists have the disadvantages of Roil saturation brought forcibly to their notice by the loss of trees from sour sap, caused by the decay of root fibre where free drainage is not available. Fertilisers are often used on land well stocked with plant food under the impression that the trees require feeding, when really the soil conditions are at fault, lack of adequqate drainage causing the soil to remain sour, or lack of cultivation prohibiting the beneficial bacteria from making plant food available. “A suitable root environment is more easily maintained in a soil well supplied with humus. The modern usage of artificial fertilisers which do not add humus to the soil make it imperative that some cover crop should be grown to supply decayed vegetable matter, without wdiich soils become sour and unproductive. In short, good drainage, constant cultivation and green crops turned in- often on on ch to maintain humus, ensures the best condition of rooting area.”