The Garden Guide

Book: Gardening Science - the Vegetable Kingdom
Chapter: Chapter 6: Plant Physiology

The accumulation of sap in plants

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1062. The accumulation of sap in plants appears to be attended with very beneficial consequences, and to be deserving of the especial attention of gardeners. It is well known how weak and imperfect is the inflorescence of the turnip tribe, when forced to flower before the fleshy root stock is formed ; and how vigorous it is after that reservoir of accumulated sap is completed. Mr. Knight, in a valuable paper upon this subject, remarks that the fruit of melons, which sets upon the plant when very young, uniformly falls off ; while, on the contrary, if the fruit be not allowed to set until the stem is well formed, and a considerable quantity of sap accumulated for its support, it swells rapidly, and ripens without experiencing any deficiency of food in the course of its growth. (Lind. Introd., 4th edit. (1848), vol. ii. p. 328.) 'The accumulation of sap, and its consequent viscidity, may, however, be attended with disadvantage to a plant, as really happens in the potato, the most farinaceous varieties of which are liable to a disease called the 'curl.' Mr. Knight attributed this to the inspissated state of the sap, which, he conceived, if not sufficiently fluid, might stagnate in, and close the fine vessels of, the leaf during its growth and extension, and thus occasion the irregular contractions which constitute this disease. He, therefore, suffered a quantity of potatoes, the produce almost wholly of diseased plants, to remain in the heap, where they had been preserved during winter, till each tuber had emitted shoots of three or four inches in length. These were then carefully detached, with their fibrous roots, from the tubers, and were committed to the soil, when, having little to subsist upon except water, not a single curled leaf was produced, though more than nine tenths of the plants which these identical tubers subsequently produced, were much diseased. The same effect has been produced by other persons, by taking up the tubers intended for seed before they were full grown, and, consequently, before the excessive inspissation of their secretions had taken place.' (Lindley's Theory of Horticulture, p. 75.)