C. M. Johnson

Comparative chlorine requirements of different plant species

SummaryRecognition of chlorine as a plant micronutrient has been extended to include ten species. Acute chlorine deficiencies or decreased yields were produced with lettuce, tomato, cabbage, carrot, sugar beet, barley, alfalfa, buckwheat, corn, and beans. Squash plants showed neither loss in yield nor other deficiency symptoms when cultured at the same time and under the same conditions as the aforementioned species. All plants acquired more chlorine during their growth than can be accounted for from seeds, inorganic salts, or water used in the experiments. Plant species least susceptible to injury when cultured upon low chlorine salt solutions were also the ones most capable of acquiring extrinsic chlorine. Of the species studied, lettuce was the most sensitive to “minus chlorine” culture solutions and squash, the least sensitive. However, the concentration of chlorine in all of the species cultured under limited chlorine supply was not greatly different. It is inferred that plants such as corn, beans, and squash survived the “minus chlorine” cultures by reason of greater accretion of extrinsic chlorine from the atmosphere. The form of the atmospherically borne chlorine is not known.

SOME ASPECTS OF LEAD IN PLANT NUTRITION

SummaryAccretion of lead by abscised barley roots from a lead nitrate solution was metabolically obtained, complemented by a fraction acquired physico-chemically. Added calcium supply did not significantly modify lead accretion. A ten-fold increase in supply concentration produced approximately a two-fold increase in lead accretion.During growth of bean, barley, and tomato plants in solution cultures, a substantial part of the lead supplied became associated with the roots; correspondingly little was present in the tops. A very large fraction of the lead associated with the roots of barley was readily extracted by various solvents, probably resident on the root surface or from free spaces therein; the remainder of the lead acquired may have been that sorbed within the root cells. A possible relationship of lead to phosphate accretion was not evident. There was no apparent effect of applied lead on the sorption of the other elements supplied. Plant dry weights, their top to root ratios and dry-weight percentages were constant under various lead supply concentrations in solution. Where lead supplies were advertently withheld, lead contents in plants were 5 to 25 times that which could have been expected under the solution culture conditions in a greenhouse with carbon filtered ambient air supply. Restriction of advertent lead supply caused no limitation of growth.If lead is essential to growth of these plant species, the critical concentration will probably be less than 2 to 6 ng atoms/g dry weight in plant tops.

Selenium and nutrition of Astragalus

SummaryAstragalus species were cultured on solutions of repurified nutrients in a greenhouse provided with carbon-filtered air. Earlier results of others which had demonstrated pronounced growth increases with selenium application are now considered to have been largely related to ameliorated toxicity of phosphate through suppressed sorption induced by selenium. Manganese sorption was similarly repressed. Losses of selenium, presumably organovolatiles, from cultures were confirmed; concomitant inadvertent accretions occurred. Essentiality of selenium for growth has not been conclusively established, but certain observations confirm the possibility. If selenium is required for growth of these species, the critical concentration will probably approximate one µg-atom Se/kg dry weight in leaves or whole plant tops.

Volatile selenium in higher plants the production of dimethyl selenide in cabbage leaves by enzymatic cleavage of Se-methyl selenomethionine selenonium salt

SummaryThe volatile selenium compound produced by cabbage (Brassica oleracea var. Capitata) when cultured on media containing either selenite or selenate is dimethyl selenide, (CH3)2 Se. The dimethyl selenide arises from enzymatic cleavage of a Se-methyl selenomethionine selenonium compound. re]19730424

Uptake and distribution of manganese in oat plants

SummaryYoung oat plants, grown in nutrient solutions, developed consistent varietal differences in Mn-concentration in the shoots. The varietal rankings, according to Mn-concentration per unit dry weight, were similar to the rankings in Mn per unit insoluble N, in Mn-uptake rate per unit root weight, and, usually, in Mn-content per plant.The varietal differences have persisted in the shoots despite variations in season and in such substrate properties as pH, Ca-concentration, iron supply, source of N, and concentration of Mn supplied. But the roots showed parallel differences only under certain conditions. Under other conditions, notably at high substrate pH or low substrate temperature, the varietal differences in the roots disappeared or even reversed. This altered the distribution of Mn between roots and shoot.

Selenium and nutrition of Astragalus: II. Ionic sorption interactions among selenium, phosphate, and the macro-and micronutrient cations

SummaryGrowth of Astragalus species was shown to be adversely affected by concentrations of phosphate in solution which are often used in inorganic nutrient media. Several ionic interactions in sorption by plants were demonstrated including depression of phosphate and the micronutrient metals by seleniteselenium, depression of selenium by phosphate, and direct or indirect enhancement of the macronutrient cations and the micronutrient metals by phosphate. Plant growth affects sorption and, conversely, repressed or excessive sorption may limit yield if the element is essential and deficient, or too high in effective concentration in the plant. Relevant interactions are considered.

NUTRIENT UPTAKE BY TUPELO GUM AND BALD CYPRESS FROM SATURATED OR UNSATURATED SOIL

SummarySeedlings of tupelo gum (Nyssa aquatica L.) and bald cypress (Taxodium distichum L. Rich.) were grown in pots containing a sphagnum moss-peat soil mix. Plants approximately 20 to 25 cm tall were subjected to three moisture treatments, saturated-aerated, saturated, and unsaturated soil; and three nitrogen fertilization treatments, control (no N added), urea (a reduced N source), and nitrate (an oxidized N source).Data include dry weights (g/culture) of leaves, stems, and roots; concentrations (percentage of dry weight) and contents (mg/culture) of N, P, K, Ca, and Mg in leaves, stems, and roots. Total dry weight was greater for plants grown in saturated-aerated soil than in either saturated or unsaturated soil. Differences in nutrient absorption and distribution between the plants and among the water treatments were principally the result of growth differences produced by the water treatments. Element contents and often the concentrations of P, K, Ca, or Mg were highest in both species when grown on the saturated-aerated soil and lowest when grown on unsaturated soil. The low levels of N in plants grown on saturated soils were probably the result of denitrification, as shown by the greater content of N in plants grown on soil fertilized with urea as opposed to nitrate. Thus, urea would appear to be a better N source than nitrate for fertilization in swamp forests. Growth of, and nutrient uptake by cypress was restricted less than that of tupelo when the plants were grown on saturated as compared to saturated-aerated soil. Thus, cypress appeared more tolerant than tupelo to the anaerobic root environment found in saturated soil.

Sulfur content of alfalfa in relation to growth in filtered and unfiltered air

The effects of sulfur on plant growth have been studied intensively by many w o r k e r s a 5 6 7 9 1 4 1 5 ~ 1 2 4 2 5 2 6 272s Roots normally absorb sulfur from the soil as sulfate, although other forms of sulfur can be absorbed and utilized by plants 2 21 2~ ~s. Sulfur in the air, from natural or industrial sources, can supply some sulfur for growth to aerial portions of plants directly as SO2 8 22 23, sulfite 24 or sul, fate 26. Appreciable, but highly variable, quantities of sulfur compounds are carried by rainfall to the soil 1 4 12 16. Minor additions of sulfate to the nutrient medium increase primarily the organic-S content of the plant but with major sulfate additions sulfate-S increases much more rapidly in the plant than organic-S iv 19 2a. I t is the purpose of the present s tudy to examine these plant-sulfur interrelationships relative to growth and sulfate supply for alfalfa grown in culture solution 10 under two environmental conditions; in an unshaded greenhouse with smogfree, carbon-filtered air and in full sunlight outdoors with unfiltered air.

Uptake and distribution of manganese in oat plants: III. An analysis of biotic and environmental effects

SummaryIn young oat plants, the mainstream of movement of Mn from nutrient solution to shoot may be regarded as passing through a labile fraction of Mn in the roots. It largely bypasses a relatively nonlabile fraction.Varietal differences in shoot-Mn can be attributed to variations in size and turnover rate of the labile fraction. Variations in pH and temperature of the substrate affect these quantities. But the effects are similar in both varieties, Sun II and Algerian, and, consequently, the varietal difference in shoot-Mn remains unmodified.Variations in total root-Mn can be largely attributed to variations in the size of the nonlabile fraction. This fraction, unlike the labile Mn, increases much more in plants of Algerian than in plants of Sun II, when the pH is raised or the temperature lowered. Consequently, the varietal difference in total root-Mn is easily disturbed by these substrate variations, and root-Mn can vary without relation to shoot-Mn.In several other varieties of oats, kinetic compartmentalisation of root-Mn could also be demonstrated. The amounts and proportions of the two forms varied widely between varieties.