STUDIES UPON WHEAT GROWN UNDER CONSTANT CONDITIONS—I

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Abstract
A pure strain of Hard Federation wheat was grown under constant conditions. Ripe (air dry) seed were obtained in 72 days. Every plant, when full grown, had 5 leaves and 1 single stem and ear. The moisture of the different organs throughout the life cycle was determined by harvesting 6 plants every other day, later on every 4th or 5th day. Sampling errors could be eliminated to a large extent by calculating the moisture and dry wt. per unit stem length or per unit leaf area and also by calculating the probable errors. From the lowest to the uppermost leaf, the dry wt. per unit leaf area increases, while the moisture decreases. Throughout the life cycle the dry wt. of the leaves increases; the moisture increases until the time of flowering. A sudden drop of moisture occurs in all the organs of the plant 1-2 days after the stamens have appeared. This drop is most pronounced in the lower leaves, sheaths, and internodes. The higher leaves lose less water and are thus able to persist longer than the lower ones. The first sign of this water loss is the yellowing of the tips of the leaves. Therefore the drying of the plant, which leads to the final death of the annual, begins as early as 1-2 days after pollination, i.e., about the time of fertilization. As an explanation of this loss of water from the different organs of the plant after flowering, the theory is advanced that the imbibition-capacity of the plasma colloids, which through the action of the growth-hormones is kept up as long as a vegetative growing point is present, decreases as soon as, through the act of fertilization, this growing point is virtually lost to the vegetative plant.

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