The influence of nitrogen, phosphate and potash on the secretion of nectar. Part I

Abstract

1. Experiments were carried out to test the effects of the three main mineral fertilizers on the secretion of nectar by apple, mustard and buckwheat. Factorial designs were used, and data on plant growth were collected in order to attempt to relate growth to nectar production. Apart from the apple trees the plants were cultivated in clean sand to which known quantities of pure minerals were added.2. Apple. The mean quantity of sugar per flower was significantly increased by extra potash; phosphate also tended to increase it. At the higher level of potash, nitrogen had significantly increased the crop of apples the previous year; it decreased the nectar yield. Potash increased nectar yield most when its effect on the crop had been small, and vice versa.3. Mustard. In this experiment the quantity of water supplied to the plants was varied as well as the fertilizers. On the last sampling occasion nectar was more frequently obtained from plants with the lower dose of nitrate than from those with the higher dose. At the high level of water, and with low nitrate, extra potash consistently increased the mean quantity of sugar per flower but with the high level of nitrate it consistently decreased it. The phosphate level had no significant or consistent influence on nectar yield.Treatments increasing nectar production tended (a) to decrease stem weight and total number of flowers; (b) to retard flower production, probably as a consequence of relatively slower growth; (c) to increase petal length, and (d) to increase the proportion of plants with orange or red pigment in the withering leaves.4. Buckwheat. Nectar was obtained significantly more frequently from those plants which had received extra nitrate and extra potash. It is suggested that the nitrate effect was due primarily to the senescent condition at the time of sampling of some of the plants with the lower dose, especially those which also had the high level of phosphate, and to the interactions of nitrate with phosphate and potash in respect to nectar production. Such explanations do not account for the effect of extra potash. Extra nitrate and potash always increased the stem weight and number of flower sprays; phosphate had little effect.