The purpose of this investigation is to determine in as definite a way as possible whether or not manganese has any important function in plant economy. The aim of this paper is to describe in a brief way some of the observations and results obtained thus far in this investigation.The method of attack has been the preparation of plant nutrient compounds and quartz sand free from manganese and the growing of plants in different portions of water cultures or sand cultures to which manganese was added or from which it was excluded. The plants were grown until
(WITH EIGHT FIGURES) In a previous report (2) it was shown that boron is essential for the growth of several varieties of lettuce; and that when it was excluded from the mineral nutrient solution, a severe deficiency disease resulted which was characterized by malformation of the more rapidly growing leaves, spotting and burning of the leaf tips, and death of the growing point of the plant. A similar condition of lettuce was described by STONE and SMITH (3) as "top-burn." They considered the cause of the disease to be physiological and promoted by unfavorable surroundings. LE CLERG (1) measured leaf temperatures, but could not establish a relation between temperature and tip burning. The writers have further investigated the disorder, from the standpoint of a nutritional deficiency.The influence of various boron compounds in preventing the burning of lettuce leaves was studied in both sand and water cultures. Control of the exact boron content of cultures was obtained by the addition of definite quantities of pure boron compounds to boron-free media. A dilute Pfeffer's solution, to which small quantities of manganese, copper, and zinc were added, supplied the basal mineral nutrients for both sand and water cult-ures. The salts composing 'the basal solution were proved to be free of boron by spectroscopical examination. Sand was purified by digestion with hot hydrochloric acid, followed by removal of chlorides with distilled water. Distilled water required for the preparation of cultures, growth of plants, purification of sand, and rinsing of containers was condensed in quartz. Porcelain dye pots and special acid-resistant jars with perforated lids were used as containers for the sand and water cultures respectively. No evidence of boron contamination from the use of these containers was observed.Lettuce seeds were germinated in purified sand, and transferred to sand or water cultures containing, with the exception of boron, all elements known to be essential for plant growth. Severe boron deficiency, as indicated by severe injury to the leaf tips, developed in from two to four weeks, depending upon the variety, amount of light, and type of culture used. Figure 2 shows leaves from normal and deficient plants of the same age. The older leaves are not noticeably affected by the absence of boron; but all young leaves, from those first affected to the growing point itself, are involved, resulting finally in the destruction of the meristem tissue and consequently in the death of the plant (fig. 3) The addition of a small quanatity of boron to the culture before the death of the growing point relieved the condition and resulted in the production of normal leaves from the growing point. The addition of boron compounds aft-er the death of the growing point resulted in growth from lateral buds in the leaf axils. Figures 4-6 show the results of continued additions of boron to the media after the development of severe deficiency, allowing the plant to make very satisfactory growth to maturity. Plants that were retarded in ...
IntroductionIodine is one of the common non-metallic elements that is widely distributed in very small quantities in nature. Iodine has a very important function in animal nutrition, .which is well established. In plant nutrition the necessity of iodine has not been clearly established. Investigations have been made on the addition of iodine as a fertilizer, the iodine content of various crops, and the effect of iodine on growth and yields of several plants. MACK and BRASHER (5) give an excellent bibliography of iodine investigations in their publication on the iodine content of certain vegetables.There is considerable conflict in the reports concerning the response of various crops to iodine treatments. The lack of uniformity of experimental conditions, however, may account for some of these differences. For example, we cite the work of LEWIS and POWERS (4) who found toxic effects of iodides at much lower concentrations than previously reported by MAZE (6) until they duplicated his nutrient solution by the addition of chlorides.The purpose of this investigation was to demonstrate the effect of varied amounts of potassium iodide on the iodine, the mineral, and the ascorbic acid content of tomato plants grown in sand cultures.
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