Relation Between the Development of Root System and Shoot Under Long- And Short-Day Illumination

Abstract

Relatively few investigations have been made to determine the factors which affect the relation of the growth of roots to tops. A more exact knowledge of the relations between aerial and subterranean plant parts and the degree to which these may be modified through cultural practices is of great scientific and practical importance. Extensive investigations have shown that plants exhibit marked specific and varietal differences with respect to relative development of roots when grown under the same environmental conditions. Intensive studies on the growth of wheat by WEAVER, KRAMER, and Ruin (20) and of certain other plants by CRIST and STOUT (3) have also made clear that there is a persistent tendency towards a positive correlation between roots and shoots, increase in size of tops being accompanied by increase in size of roots. Although significant variations in the relative distribution of the growth rate of tops and roots occur in nature and may readily be induced by change in environment, the fact remains that there is a persistent positive correlation in size of tops and roots regardless of the wide variations induced by special conditions.The maintenance of a proper balance between root and shoot is of very great importance. If either is too limited or too great in extent, the other will not thrive. The root system must be sufficiently widespread to absorb enough water and nutrients for the stem and leaves, which, in turn, must manufacture sufficient food for the maintenance of the root system. The plant is a biological unit although it is frequently not treated as such. It is often mutilated by pruning, cutting or injuring the root system, frequently without much regard to the effect upon the remaining portion.JEAN and WEAvER (7), HARRIS (6), and others have shown that the general effect of decreased water content of soil, providing enough is available to promote moderate growth, is to accelerate root development in relation to growth of tops. Low humidity resulting in high transpiration gives similar effects. MAxIMOW and LEBEDINCEV (13)

Effects of Photoperiod and Nitrogen Supply on Growth and Reproduction in the Gherkin

“…In the present instance, gherkin plants receivinig 16 hours of illumination daily excelled in most growth responses, judged on the basis of yield. Reduction in total weight under short-day illumination coincides with the observations of several investigators (11,13,39) working with a variety of photoperiodic and inideterminate plants. A laroer proportion of the total carbohydrate contenit of the short-day plants was in the insoluble form.…”

Growth and Nutrient Responses of Little Turkish Tobacco to Long and Short Photoperiods

“…This response, coupled with a longer vegetative period of growth, suggests an eventually greater vegetative yield of the short-day plants at maturation. WEAVER and HIMMEL (26), working with a number of photoperiodic plants found that under short-day illumination the growth of both tops and roots was greatly retarded, approximately to the same degree in both longand short-day species. In the present experiment with tobacco simiiilar results were obtained, except that the development of the roots was retarded to a greater degree than the tops by short day during the rosette and elongation stages.…”

Effect of Variation in Length of Day on Growth and Dormancy of Trees

“…Experiments on herbaceous plants have shown that there are changes in hydrogen-ion concentration and hydration of tissues (8), carbohydratenitrogen relations (20,24), root-shoot ratios (25), and catalase activity (15), and similar changes doubtless occur in woody plants. The rate and amount of photosynthesis is doubtless affected and it has been shown that in some plants the utilization of nitrates is also affected (20).…”