Showing papers in "Plant Physiology in 1961"

Metabolic fractionation of C13 & C12 in plants

Abstract: C/sup 13//C/sup 12/ ratio analyses of chemical fractions from several plant phyla show that in all cases the lipid fraction is enriched in C/sup 12/ compared to the whole plant. The C/sup 13//C/sup 12/ r atio of the plant lipids corresponds roughly to the C/sup 13//C/sup 12/ ratio of petroleums. The C/sup 12/ enrichment in petroleums a compared to present day plants can be explained if selective preservation of plant lipids occurred during the sedimentation process. The degree of C/sup 12/ enrichment in the plant lipid fraction is inversely related to the amount of lipid in the plant. The C/sup 12/ enrichment which occurs in plant lipids may be balanced by the C/sup 13/ enrichment which occurs in respired CO/sub 2/. Isotope selection at the level of acetate or pyruvate is a possible mechanism for explaining our results. (auth)

Inhibitors of the Hill reaction.

Abstract: Many commercially important herbicides seem to kill plants by inhibiting photosynthesis. Wessels and van der Veen have shown that leaves or parts of leaves treated with phenylureas irreversibly lose all ability to assimilate CO.,. They also found that chloroplasts treated with phenylureas are unable to reduce oxidants such as 2,6-dichlorophenolindophenol in the light (20). A wide variety of phenylcarbamates similarly inhibit photochemical reductions by chloroplast (the Hill reaction) although somewhat higher concentrations of these carbamates are required (20, 11). Recently a number of acylanilides have been intro(luced as herbicides. These, too, interfere with the Hill reaction (12). The phenylcarbamates, phenylureas, and acylanilides are, of course, closely relate(d chemically: all are anilides of carboxyacids. However, the very (lissimilar herbicide Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] also inhibits the Hill reaction and does so at low concentrations (13).

Influence of calcium on selectivity of ion absorption process

Abstract: Several polyvalent cations affect absorption by excised plant roots similarly to calcium Magnesium appears to be an exception It is suggested that either the particular mechanism involved is not specific for calcium or that the polyvalent cations act via a calcium interaction Calcium was found to have the property of drastically altering the ratio of absorption of scdium and potassium from a mixture of the two Using lithium and Na + K solutions it was shown that the absorption system was extremely sensitive to smal1 concentrations of calcium As little as 10/sup -6/ M calcium was suificient to cause a detectable change in absorption rates The effect of calcium is enhanced in mixtures of sodium and potassium compared to its effect in single salt solutions The essentially constant sum of the absorptions of sodium and potassium in spite of large changes in the ratio of absorbed sodium and potassium caused by the presence of calcium suggests a common metabolic carrier The controlling behavior of calcium was found in the roots of six different species of plants This may indicate a widespread occurrence (auth)

Formation of auxin from tryptophan through action of polyphenols

Abstract: Plant preparations that convert tryptophan to indoleacetic acid (IAA) characteristically have low reaction yields. Since such preparations sometimes also contain IAA-oxidase activity, inhibition of the oxidase might raise the yields of IAA. Accordingly, polyphenolic inhibitors (1, 11, 19, 33, 40) were added to incubation mixtures containing tryptophan and a seedling enzyme preparation that was able to convert tryptophan to IAA. More than tenfold increases in auxin yield resulted. However, the presence of auxin in enzymeless controls, plus experiments on the recovery of added IAA, indicated that the enhancements observed might be caused by a polyphenolic oxidation of tryptophan to IAA. We shall present evidence that the sequence

Transpiration stream & ascension of calcium

Abstract: Since Cline's report (5) of a very slow equilibration in the leaves of tritiated water absorbed by the roots of bean plants, no resolution has been made between his expressed alternative views that this was due A, to failure of tissue water to exchange with the incoming tritium-labeled water, or B, to a large isotope effect. During the preparation of the present manuscript Vartapetyan and Kursanov (14), using HO'8-enriched water in the nutrient solution, have also reported a slow equilibration of this tracer in the leaves (& roots) of the bean plant. In addition, they grew sunflower plants from seed with H.018enriched water and observed almost complete equilibration in all parts of the plant and thereby showed that the failure to equilibrate was due to failure of mixing, and that there remained the possibility of only an insignificant isotope effect. Even this was explainable by unlabeled water brought into the experiment in the seed, or to the formation of metabolic water in which there was a slight isotope effect. Our report confirms the slow equilibration in leaves of the labeled water delivered in the transpiration stream, and in addition shows the progress of the labeled water through the stem and into the leaves in a way which discloses the path and manner of movement of the transpiration stream. The Ca45 isotope was used with the tracer water in order to compare the ascent of a mineral marker. Calcium was selected as it is not subject to a significant redistribution from leaves and could be expected to reside in the leaves into which it was delivered (4). The degree of dependence between the movement of a mineral component and the movement of the transpiration stream has never been satisfactorily investigated. The traditional concept is that mineral nutrients move upward in the xylem vessels in conjunction with the transpiration stream; once started the water and minerals move together and, with the exception of those salts removed by absorption along the way, reach their final destination in the leaves (6). The data obtained in the present study indicate that neither

Hexitols in coconut milk: Their role in nurture of dividing cells

Abstract: Coconut milk, the liquid endosperm of the coconut (Cocos nucifera L.), has special interest because it will induce otherwise mature, non-growing cells to divide and to grow rapidly (3, 4). Similar properties reside in analogous morphological situations, such as the immature caryopsis of Zea mays and the liquid present in immature fruits of Juglans (18) or of Aesf alus (12, 24, & also see 25). A nutritive relationship also exists between the female gametophyte, sometimes called endosperm, and the archegonia and embryos of the gymnosperm Ginkgo; extracts of this gametophyte will also induce cells of mature tissue of carrot root to resume active growth (18). Therefore, the fluids that nourish immature embryos seem especially able to induce growth in the mature cells even of some other plants than the ones in which they were laid down. This raises the question whether the behavior of the zygote is due to its special nature or to its nurture by the special fluid contents of the embryo sac, by the substances which are contained in the endosperm, and by other special nutritive organs. Free cells obtained from mature carrot phloem may be cultured in media which contain coconut milk (21) and may grow and regenerate a complete and mature plant (20). In this7 respect the free cells imitate the zygote, and the coconut milk its normal nutritional supply. Moreover, as the cells grow and develop, they form structures which are strongly reminiscent of pro-embryonic development (15). Therefore, a full knowledge of the chemical constituents of coconut milk which cause these growth responses would have an important bearing upon many problems of cell growth and cell division. This knowledge would also have important implications for protein synthesis, which is stimulated in quantity and modified in kind during the induction of growth in carrot and potato cells (27). Following the observations of Blakeslee and van Overbeek (28, 29), work upon the chemical constituents of coconut milk was pursued sporadically in different laboratories (for references see 25). In this laboratory, investigation has been in progress for some years. Clearly, the growth induction which is pr,oduced by the coconut milk, over and above the effects due to common nutrients and vitamins, is not a simple effect due to a single substance. On the contrary, it has been emphasized that no substance singly and independently controls cell division (see 25 & references there cited). In part the effect of coconut milk is non-specific and is replaceable by casein hydrolysate, or by other sources of the reduced nitrogen compounds, from which the cells may synthesize protein more readily than they do from nitrate (13). Even whole coconut milk alone will not trigger the growth of some cells (e.g. potato tuber), for it needs to be supplemented by one of a large array of compounds which are now known to act synergistically with the coconut milk. The substance 2,4-dichlorophenoxyacetic acid (2,4-D), and many of its analogues with different ring configurations or different side chains, can also function in this manner (14,16, see also 25). Several of the halogen-substituted phenylacetic acids (26) and certain a-substituted propionic acids (14) can also work along with the coconut milk. This paper now designates certain hexitols to be responsible for part of the effect for which coconut milk (or its morphological equivalent) has hitherto been regarded as a specific source. Early work on the chemical fractionation of coconut milk and similar fluids recently has been reviewed (25). This work encountered the difficulty that, when purified, the isolated substances only expressed their activity in the presence of other sub-fractions from the coconut milk. While this statement still holds true, the work to be described permits the critical identification of at least three of the synergists which contribute to the total growth which is stimulated by whole coconut milk.

Physiological effects of gibberellic acid. III. Observations on its mode of action on barley endosperm

Abstract: Perhaps the most striking aspect of the normal germination of barley is the correlation between the simultaneous breakdown of reserve carbohydrates and proteins in the endosperm and the growth of the embryo. During germination there are large increases in the activity of hydrolytic enzymes such as the amylases, proteinases, and cytases in the endosperm. The liberation of sugars and amino acids has been correlated with the changes in enzyme activity. On these grounds, it has been suggested that hydrolytic enzymes are responsible for mobilizing the endospermic reserves. The identity is known of some, though by no means all, of the hydrolytic enzymes that may be involved. However, it is not known whether the processes involved with the hydrolysis of starch and the hydrolysis of protein are activated separately or whether they are initially controlled by a common reaction. Sachs, in 1887 (10) recognized the necessity for embryo action before the hydrolytic processes can begin. James, in 1953, restated the original concept when he wrote, "The relationship of the germinating embryo to the endosperm is virtually that of a parasite extruding exo-enzymes into the host tissues, much as a spider treats a fly" (3). This theory was based almost entirely on the fact that the endosperm exhibits a very low rate of respiration during germination. Since some enzymes, notably a-amylase. are found only after germination, James assumed that only enzyme synthesis could account for their presence and that the endosperm, with its very low respiratory rate, could not be the seat of such synthesis. There is now reason to believe. however, that this explanation may not describe all of the processes involved. Gibberellic acid (GA3) is capable (in the excised endosperm in the complete absence of the embryo) of activating starch hydrolyzing enzymes, including a-amylase (9), and releasing reducing sugars (i.e. mobilizing the starch reserves) (8). On the basis of these results it was tentatively suggested (9) that a gibberellin-like hormone may act in vivo in a similar manner, being produced in the embryo and secreted into the endosperm where the hormone would bring about effects similar to those described. In other words, the interdependence between barley embryo growth and the hydrolysis of endospermic reserves would be maintained. The embryo would supply the stimulus or contr,olling agent in the form of an endogenous gibberellin-like hormone and the endosperm would supply the energy sources necessary for continued growth and development. The processes occurring in the endosperm during germination, however, involve all of the endosperm constituents and not merely those involved with carbohydrate metabolism. This fact prompted an investigation into the further aspects of the GAo effect on excised endosperm.

Invertase & invertase inhibitor in potato.

Abstract: The pattern of changes in sugar composition which occur when potatoes are stored at low temperatures or are irradiated (18, 19) suggests that the reducing sugars mnay arise as the consequence of the hydrolytic action of invertase on sucrose. During cold temperature storage there is a rapid increase in sucrose content followed bh an increase in redlucing sugars relative to the sucrose content. Furthermore a survey of the literatur-e indicates that, for many varieties of potatoes, the ratio of glucose to fructose is close to unity (luring at least part of the time of storage (17). If invertase is indleed a factor in the accumulation of reducing sugars, information concerning the characteristics of this enzyme and the inhibitor here reported could conceivably lead to nmeans for controlling the reducing sugar content of potatoes (20). The literature on potato invertase is rather sparse. Tn 1903, Kastle and Clark (9) detected invertase in sprouted but not in unsprouted potatoes. In 1928, MlcGuire and Falk (13) showed that the invertase action of potato juice was higher at pH 4 than at pH 5 and 6. Denny et al (5) found that the invertase activity of potato juice from tubers treated with ethylene chlorohvdrin was significantly greater than that fronm untreated controls. A few reports have suggested that the level of invertase activity depends on the elemental nutrition of the plant [potassium (24), boron (4), chlorine & sulfur (10)1. Bois and Savary (3) and MIcCready (12) in more recent years have detected invertase in potatoes, although the latter author could fin(d activity only in sprouted andl not in unsprouted tubers. The presenlt paper describes our experience in attempting to (letect invertase in crude potato macerates. In general, the results confirnm the scattered findings of the older literature but also point to the presence of an endogenous inhibitor of the enzymiie. A preliminary report of some of the present results has been publishedl elsewlhere (21).

Distribution of boron in leaves.

Abstract: culture methods for growing plants without soil. Cal. Agr. Exp. Sta. Cir. 347. 6. ILJIN, V. S. 1951. Metabolism of plants affected with lime-induced chlorosis (Calciose). Plant & Soil 3: 339-351. 7. ILJIN, V. S. 1951. Metabolism of the grapevine during lime chlorosis. Gardenbauwirs. 17: 33,R-381 (Abst. in Chem. Abs. 28: 6332) 8. ILJIN, V. S. 1945. Salts & organic acids in relation to calciophiles. Flora 37: 265-299. (abstract in Chem. Abs. 39: 4113) 9. LINDSAY, H. L. & D. W. THORNE. 1954. Bicarbonate ion & oxygen level as related to chlorosis. Soil Sci. 77: 271-279. 10. NEISH, A. C. 1949. Production & properties of 2,3-butanediol. Canadian J. Res. 827: 6-8. 1 1. RHODES, W. A., A. WALLACE, & E. M. RommMEY. 1959. Lime-induced chlorosis studied-physiology of disorder investigated to learn role of malonic acid & possibility of a block in organic acid metabolism. Cal. Agr. 13(3): 6. 12. SAYWELL, L. C. & B. B. CUNNINGHAM. 1937. Determination of iron, colorimetr c o-phenanthroline method. Ind. & Eng. Chem. Ann. Ed. 9: 67-69. 13. SCHANDER, H. 1944. The differences & similarities of chlorosis in lupines & wood growth. Gardenbauwiss. 17: 304-369. 14. SCHANDER, H. 1945. The dependence upon external factors of chlorosis of lupines leteus seedlings in sand cultures. Bodenk u Pflanzenernahr. 12: 71-84. 15. SCHANDER, H. 1945. The problems of lime chlorosis in plants. Tohrb. Wiss. Botan. 91: 169-185. (Abstr. in Chem. Abs. 39: 4649.) 16. \VADLEIGH, C. H. & J. C. BROWN. 1952. The chemical status of bean plants afflicted with bicarbonate-induced chlorosis. Botan. Gaz. 113: 373-390. 17. YOUNG, R. H. & L. M. SHANNON. 1959. Malonate as a participant in organic acid metabolism in bush bean leaves. Plant Physiol. 34: 149-152.

Uptake of calcium by excised barley roots.

Abstract: The uptake of calcium by 6-day-old excised barley roots appears to be largely non-metabolic. The calcium uptake at pH 5 was found to be insensitive to low temperature and dinitrophenol. The uptake of Cals was a reflection of isotopic exchange for initially present inert calcium in the root. This equilibration process was not affected by dinitrophenol. There was a large uptake of calcium by this material at pH 11. This uptake was also largely non-metabolic. Only a small fraction of the calcium uptake at high pH could be accounted for by an increase in organic acids or by precipitation as CaCO3. It is postulated that much of the calcium in young barley roots is associated with the cell surface region. Finally, it is proposed that the calcium which is active in influencing the absorption of other ions is localized on this surface.

Suspension cultures of higher plant cells in synthetic media.

Abstract: The cultivation of cells from higher plants is a technical advance in plant tissue culture research which opens new avenues of investigation into cellular and physiological problems. Successful culture of higher plant cells as suspensions in liquid media of complex constitution has been reported by several research groups. Isolated cells or cell suspensions produced in culture have been used in a variety of problems, including the study of cell division [Muir et al, (9, 10); deRopp (5); Torrey (18); Steward et al, (16); Braun, (4) ; Jones et al, (7)], susceptibility of tissues to virus infection [Hildebrandt, (6) ; Bergmann, (2)], cellular differentiation [Steward et al, (15); Reinert, (12)], the production of cell metabolites [Tulecke & Nickell, (21)]. Still many problems remain untouched. The production of cell suspensions has been achieved to date only with complex nutrients such as coconut milk, yeast extract, or other complex media, which limit the usefulness of the technique, especially where analysis of chemical changes is desired. Our purpose is to report relatively simple techniques devised to allow the cultivation of large numbers of isolated viable cells in suspension under defined nutrient and cultural conditions. We give an account of the course of development of liquid cultures with respect to increases in fresh weight and numbers of cells in suspension.

The reductive pentose phosphate cycle. III. Enzyme activities in cell-free extracts of photosynthetic organisms.

Abstract: The reductive pentose phosphate cycle (6, 29, 8) is currently believed to be the pathway by which CO2 is converted to carbohydrate in photosynthesis. Evidence for the functional role of this cycle is derived mainly from isotope experiments. Brief exposure of photosynthesizing algae to C1409 produces radioactive 3-phosphoglycerate (3-PGA ) 3, labelled mainly in the carboxyl group ( 11 ). The cyclic nature of the photosynthetic carbon path is indicated by the subsequent appearance of isotopes in the a and /8 positions of 3-PGA, as well as in phosphate esters of ribulose and sedoheptulose (28). Kinetic studies by Calvin and Massini (14) and Bassham et al (7) on the fluctuation of pool sizes, revealed that transition from light to dark resulted in an increased concentration of 3-PGA accompanied by a decreased concentration of sugar diphosphate. Studies (43) carried out with algae subjected to changing partial pressures of COO demonstrated a fall in 3-PGA and a rise in ribulose diphosphate (RDP) concentration when the CO., concentration was changed from 1 % to 0.003 %. Enzymes of the pentose phosphate cycle are ubiquitously distributed (2, 4, 5, 17, 18, 20, 21, 22, 23, 24, 28, 29, 30, 36, 37, 38, 41). However, no single photosynthetic organism has been shown to possess all of the requisite enzymes and in amounts sufficiently high to support photosynthesis by this pathway. In this report, the quantitative aspects of all the pentose phosphate cycle enzymes in extracts of several photosynthetic organisms were investigated. We compared the rate of photosynthetic CO2 fixation of the intact organism with the enzyme capacities (activities at saturating substrate concentration) in an extract of the same organism. Our results indicate that several en-

Uptake of magnesium & its interaction with calcium in excised barley roots.

Abstract: 1. BORTHWICK, H. A. & S. B. HENDRICKS. 1960. Photoperiodism in plants-control of plant growth by light & the measurement of night length. Science 132: 1223-1228. 2. HENDRICKS, S. B., H. A. BORTHIWICK, & R. J. DOWNS. 1956. Pigment conversion in the formative responses of plants to radiation. Proc. Nat. Acad. Sci. 42: 19-26. 3. BORTHWICK, H. A., S. B. HENDRICKS, E. H. TOOLE, & VIVIAN K. TOOLE. 1954. Action of light on lettuce seed germination. Botan. Gaz. 115: 205225. 4. NELSON, M. L. 1940. Light influences germination of southern pine seed. South. For. Exp. Sta. Notes 31. 5. TOOLE, E. H., VIVIAN K. TOOLE, H. A. BORTHIWICK, & S. B. HENDRICKS. 1955. Plhotocontrol of Iepidiurn seed germination. Plant Physiol. 30: 15-21.

Isolation of indole-3-acetic acid from corn kernels & etiolated corn seedlings.

Abstract: Inidole-3-acetic acid (IAA) has been commonly accepted as an inmportant plant auxin (4,14, 20). Grain of corn (Zea mtlavs L.) is a rich source and milligram quantities have been isolated by alkaline hydIrolysis of the nmature kernels (2, 16), or by direct extraction fronm immature kernels (15). A numner of reports have appeared concerning occurrence of TAA in vegetative portions of plants, but in many cases diethyl ether has been used as the extracting solvent in a manner which can allow the enzymatic conversion of tryptophan to IAA (40). In other cases, tlle existence of IAA is presumed from the bioassay of chromatogranms run in a single solvent. Thus proof that free TAA is generally distributed in growing plant tissue is not yet available (1). In a previous studly (35), relatively large amounts of TAA have been detected in Ustilago Zeae (Beckm.) Ung. tunmors and smaller amounts in healthy, earlytassel-stage corn stalks. The objective of the present study xvas to isolate free TAA from vegetative plant tissue using sufficiently rigorous isolation and assay procedures to establish its idlentity. Methods were developed to permit the use of kilogramii quantities of plant tissue, and the additioni of trace amlounts of TAA-2-C14 facilitate(d evaltuation of losses (luring isolation.

Red, far-red response & chlorophyll synthesis.

Abstract: One of the earliest observations on the photomorphogenic development of chlorophyll synthesis was made by Withrow et al. (10). In a preliminary report they noted that pretreatment of leaves with up to 10 millijoules (mj/cm2) of red radiant energy followed by a dark period of from 5 to 15 hours, resulted in the elimination of the latent period in subsequent chlorophyll formation, with some indication that the red induction might be reversed by an exposure to far-red. Virgin verified this observation of the involvement of the photomorphogenic induction effect on the development of the chlorophyll synthesizing mechanism (6) and demonstrated the greater effectiveness of red over blue pretreatment (7). Althouggh the induction response has been clearly demonstrated, the far-red reversal phenomenon associated with chlorophyll synthesis has not been previously shown. The data herein presented establish clearly that chlorophyll synthesis is another of the physiological responses referred to as red, far-red reactions, in which stimulation of plastid pigment synthesis by a short red preirradiation may be nullified by a subsequent far-red pretreatment. However, the red, far-red effect on chlorophyll synthesis is not directly associated with the photoconversion of protochlorophyllide (11). It is, rather, a reflection of metabolic and growth changes affecting the rate of synthesis of protochlorophyllide, these growth and metabolic changes having been induced by means of the primary effect of light on the photomorphogenic pigment receptor (4).

Negative transport & resistance to water flow through plants

Abstract: Negative transport is the downward conduction of water in the plant. This phenomenon has been studied by several investigators, yet considerable controversy about several aspects of the problem still exists. The portion of the leaf through which water enters is obscure. Meidner (16) suggested that specialized epidermal cells of the plant, Chaetachme aristata were involved in the phenomenon. Gessner (8) decided that most of the water was absorbed directly through the cuticle. Most investigators (4, 23) have considered that no water enters through the stomates (except perhaps a small amount of water vapor). Breazeale, McGeorge, and Breazeale (2, 3) investigated the absorption of water by leaves and its subsequent transport through the plant to the soil surrounding the roots. They concluded that tomato plants could grow to maturity, flower, and set fruit with no other source of water than that absorbed through the leaves from an atmosphere of 100 % humidity. They demonstrated that tomato plants can absorb water from a saturated atmosphere, transport it to the roots, and build up the soil moisture to or above the field capacity. Other investigators repeated the experiments of Breazeale but could get no evidence of actual water secretion by roots (9, 10, 25). Stone, Shachori, and Stanley (22) concluded that negative transport occurs only when the temperature is allowed to fluctuate and is caused by vapor pressure gradients and not by any active secretive force within the plant itself. Slatyer (20, 21), who reviewed these studies, stated that the main reason for lack of transport into soil is lack of an adequate gradient. The movement of water in plants has been studied from two different approaches: I. Some investigators have considered the entire soil-plant-atmosphere system (1, 6, 19, 24). They applied an analogue of Ohm's law and showed that water transport is controlled by the potential difference across the section and the resistance within the segment. This theory also proposes the important consideration that the rate of movement is governed by the point or region of greatest resistance in the system. Those who have studied this theory agree that the greatest resistance under natural conditions is usually located at the leaf-atmosphere interface where the water is converted from liquid to vapor. Most of these studies seem to be based more upon theoretical arguments than direct experimental results. II. Other scientists have investigated the movement of water in plants by studying some particular part of the system, such as the flow of water in the roots, leaves, or stem. Resistance to water flow in the conducting tissue of the stem is generally considered to be small as compared to other parts of the plant (5, 13, 15, 17). Some researchers have found the resistance in the roots is much larger than in the stems (12, 13, 14). Others have observed that the resistance in leaves is larger than in stems and roots (26). The resistance in the vascular elements can become larger when very small diameters are encountered (7, 27). It has also been indicated that the resistance to water flow is uniform through the cell walls, membranes, and vacuoles of plant tissues (1, 19). The experimental evidence to support these concepts is meager and inconclusive. Experimental measurements of the relative magnitude of the resistance of the stem, leaves, and roots to water flow in the absence of a water phase change have been made. This gives evidence of the relative contribution of the several plant parts to water flow resistance without the complicating factor of vaporization. Once this contribution to water flow resistance is known then studies can be made to combine the vaporization and vapor diffusion resistance as well as the soil resistance to water flow to the absorbing root surface. These experiments have also produced some information about negative transport.

Formation of sucrose from malate in germinating castor beans. I. Conversion of malate to phosphoenol-pyruvate.

Abstract: composed of all the valence electrons of the specimen. In this case, the electrons of the metal are coupled via the photon gas; their actions are not completely independent. Such a situation is not the case in the usual photosynthetic system; equilibrium or quasiequilibrium ideas may not be applied. In this situation each photosynthetic event is completely independent of the other events taking place at other sites in the material. Although in such a complicated system as the photosynthetic unit there could conceivably be a number of events which would use up the electronic energy imparted by photon absorption (such as fluorescence, radiationless transition, etc.). the individual photoelectron interactions are beyond the region of applicability of the second law of thermodynamics and are limited only by the conservation of energy and momentum. ACKNOWLEDGMENT

Influence of cobalt on nitrogen fixation by medicago.

Abstract: 1. ARCHBOLD, H. K. 1942. Physiological studies in plant nutrition. XIII. Experiments with barley on defoliation and shading of the ear in relation to sugar metabolisnm Ann. Botany 6: 487-531. 2. BAIN, J. M. 1958. Morphological, anatomical, and physiological changes in developing forms of Valencia orange. Austral. J. Botany 6: 1-24. 3. Br.Aw, R. C. and G. W. TODD. 1960. Photosynthesis and respiration in developing fruits. I. C'402 uptake by young oranges in the light and in the dark. Plant Physiol. 35: 425429. 4. EAKS, I. L. and W. A. LUDI. 1958. Response of orange and lemon fruits to fumigation with ethylene dibromide effective against eggs and larme of the Oriental and Mexican fruit flies. Am. Soc. Hort. Sci. Proc. 72: 297-303. 5. EATON, F. M. and H. E. JOHAM. 1944. Sugar movement to roots, mineral uptake, and the growth cycle of the cotton plant. Plant Physiol. 19: 507518. 6. HusSEIN, A. A. 1944. Respiration in the orange. A study of systems responsible for oxygen uptake. J. Biol. Chem. 155: 201-211. 7. KosKi, V. M. 1950. Chlorophyll formation in seedlings of Zea mays L. Arch. Biochem. 29: 339343. 8. KURSANOV, A. L. 1934. Die Photosynthese gruner Fruchte und ihre abhangigkeit von der normalen Tatigkeit der Blatter. Planta 22: 240-250. 9. TURRELL, F. M. 1946. Tables of surfaces and volumes of spheres and of prolate and oblate spheroids and spheroidal coefficients. University of California Press, Berkeley. 10. WATSON, D. J. and A. G. NORMAN. 1939. Photosynthesis in the ear of barley and movement of nitrogen into the ear. J. Agr. Sci. 29: 321-345.

Osmotic & specific effects of excess salts on beans.

Abstract: In analyzing the cause of growth depression of plants raised under saline conditions, a distinction can be made between effects that are specific and those that are non-specific, with respect to the different salt species present in the root environment (1). Non-specific effects are related to the total concentration of salts, regardless of species. They prevail among the factors that determine the partial molar free energy of water, from the gradients of which depend the magnitude of the driving force, as well as the direction pertinent to the translocation of water in both soils and plants. Known as osmotic effects, nonspecific effects of salts are of a physico-chemical nature where they refer to the nutrient or soil-solution. They are barely distinguishable from physiological effects where they influence the state of water within the plants, as it may have bearing on cell processes. Both types of osmotic effects are associated to the extent that plants are capable of adjusting their internal osmotic pressure (OP) relative to changes brought about in the external OP (6, 8). Specific effects are usually due to the relative concentrations of the various ion species with respect to one another, less frequently to the absolute level of any one element. Their influence is essentially of a physiological nature. Changes in the osmotic concentration within plant cells brought about by varying relative ion concentrations in the growth medium kept at a constant OP should also be recognized as specific effects. Osmotic effects are frequently confounded with specific effects because high total-salt levels normally occur in association with ionic conditions that are unbalanced with respect to plant nutrition. Other specific effects, like trace element toxicities, are usually unrelated to osmotic effects (27). In many solution-culture studies purporting to separate the impact on plant growth due to osmotic effects from that due to specific effects, single salts (8, 9), mixtures of various salts (15), or organic compounds (10), have been used to control the OP of the solutions. Isosmotic solutions containing NaCl, Na,SO4, or CaCl2, caused equal depressions in growth of kidney beans (9), and in water uptake by corn roots (10). Both water uptake and growth were linearly related to the concentrations of any of the three salts in solution. To the extent that isosmotic concentrations of different salts cause equal growth depressions, such as in the examples cited, osmotic effects are predominant. Less likely, though sometimes not impossible, is the alternative explanation that the specific effects of the different salts on the test plant are nearly similar. Any variation in plant response to isosmotic concentrations of different salts indicates the additional significance of specific effects. For instance, MgCl2 and MgSO4 depressed the growth of kidney beans significantly more than did NaCl, Na,SO4, or CaCl9, all salts being compared in isosmotic concentrations. No proportionality existed between growth and Mg-salt concentration (9). With guayule as a test plant, neither was there a proportionality between growth and concentration of any one of the five salts mentioned, nor did the different salts when present in isosmotic concentrations cause the extent of growth depression to be the same. In fact, it appeared that MgCl was most, and CaCl least, toxic (24). Attempts to distinguish between osmotic and specific effects on plant growth require the aid of a compound that, while lowering the partial molar free energy of water, at the same time itself is as inert as possible with respect to the metabolism of the plant species tested. The latter requirement has not always been sufficiently considered. Substances like polyvinylpyrrolidone (26) and polyvinyl alcohol (5) in concentrations equivalent to 1 atm OP have been observed to be toxic to dwarf red kidney beans (11). Other substances, like sucrose, are either actively taken up or, like mannitol, subject to quick microbiological degradation. The usefulness of the compounds mentioned for osmotic studies of any extended length of time is dubious. A search for an osmoticum of the desired qualities has resulted in the selection of Carbowax polyethylene glycol, of a molecular weight of about 20,000, marketed by the Union Carbide Chemicals Co. (11). This compound henceforth will be referred to as C20M. Carbowax polyethylene glycols of lower molecular weights have been applied for various purposes, but no observations have been reported with regard to any physiological toxicity to plants (16). C20M contains considerable amounts of aluminum and magnesium (11). These impurities would have to be removed prior to applying C20M to most plants. Our paper will present details on the application of dialyzed C20M to distinguish I Received February 23, 1961.