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The chloroplasts from wheat leaves developed under intermittent illumination (1 ms light + 12 min dark) were able to photoreduce DPIP with DPC as electron donor but unable to photoreduce DPIP with water as electron donor. On exposure of these leaves to continuous light, the Hill activity with water as electron donor was rapidly induced. The photoactivation was sensitive to the treatment with DCMU prior to exposure to continuous light. The action spectrum for the photoactivation showed a sharp band at 680 nm with a distinct shoulder at 650 nm, and was similar to the absorption spectrum of photosytem-2 particles. These data suggest that the electron transfer driven by photosystem 2 is essential for the activation of the water-splitting system in the chloroplasts of intermittently illuminated leaves. [ABSTRACT FROM AUTHOR]

Conditions are described for measuring anthranilate synthetase, anthranilate‐PRPP‐phosphoribosyl transferase, N‐5′‐phosphoribosyl anthranilate isomerase, indole‐3‐glycerol phosphate synthetase and tryptophan synthetase in crude extracts from Triticum aestivum (wheat) plants. Only the last enzyme has been measured before in extracts from green plants. The extractable quantities of each enzyme in all plant parts at all stages of growth were sufficient to synthesize the amount of tryptophan present within the same tissue in 48 h. Anthranilate synthetase activity was the lowest of the five enzyme activities and was the only one inhibited by tryptophan in vitro, indicating that this enzyme may be the control point in tryptophan biosynthesis in wheat plants. [ABSTRACT FROM AUTHOR]

Wheat seedlings were subjected to heat shock for 2 min at 45°C. The seedlings were then incubated at 25°C or higher temperatures (usually 35°C). At 25°C the root tips survived the heat shock, but not at temperatures above 34°C, unless they had been pretreated with ethanol or kinetin, After 1 h in ethanol and after more than 15 h in kinetin the root meristem survived a high incubation temperature after the heat shock. Immediately after heat treatment the glyceride content in treated root tips was higher than in untreated roots. The same was observed after heat treatment of root tips pretreated in ethanol and kinetin. The content of ether extractable lipids was not changed by the heat shock. [ABSTRACT FROM AUTHOR]

The effects of fluoride on respiration of plant tissue and mitochondria were investigated. Fumigation of young soybean plants (Glycine max Merr. cv. Hawkeye) with 9–12 μg × m−3 HF caused a stimulation of respiration at about 2 days of treatment followed by inhibition 2 days later. Mitochondria isolated from the stimulated tissue had higher respiration rates, greater ATPase activity, and lower P/O ratios, while in mitochondria from inhibited tissue, all three were reduced. Treatment of etiolated soybean hypocotyl sections in Hoagland's solution containing KF for 3 to 10 h only resulted in inhibition of respiration. Mitochondria isolated from this tissue elicited increased respiration rates with malate as substrate and inhibited respiration with succinate. With both substrates respiratory control and ADP/O ratios were decreased. Direct treatment of mitochondria from the etiolated soybean hypocotyl tissue with fluoride resulted in inhibition of state 3 respiration and lower ADP/O ratios with the substrates succinate, malate, and NADH. Fluoride was also found to increase the amount of osmotically induced swelling and cause a more rapid leakage of protein with mitochondria isolated from etiolated corn shoots (Zea mays L. cv. Golden Cross Bantam). The results are discussed with respect to possible effects of fluoride on mitochondrial membranes. [ABSTRACT FROM AUTHOR]

Nitrite and nitrate uptake by wheat (Triticum vulgare) from 0.5 mM potassium solutions both showed an apparent induction pattern characterized by a slow initial rate followed by an accelerated rate. The accelerated phase was more rapid for nitrate uptake, was initiated earlier, and was seriously restricted by the presence of equimolar nitrite. The accelerated phase of nitrite uptake was restricted by nitrate to a lesser extent. The two anions seem not to he absorbed by identical mechanisms. Ammonium pretreatments or prior growth with ammonium had relatively little influence on the pattern of nitrite uptake. However, prior growth with nitrate eliminated the slow initial phase and induced development of the accelerated phase of nitrite uptake. A beneficial effect was noted after 3 h nitrate pretreatment and full development had occurred by 12 h nitrate pretreatment. The evidence suggests that a small amount of tissue nitrite, which could be supplied either by absorption or by nitrate reduction, was specifically required for induction of the accelerated phase of nitrite uptake. Cycloheximide (2 μg ml-1) seriously restricted development of the accelerated phase of nitrite uptake, but its effect was not as severe when it was added after the accelerated phase had been induced by prior exposure to nitrite or nitrate. However, translocation of 15N from the absorbed nitrite was sharply decreased under the latter conditions, indicating a difference in sensitivity of the uptake and translocation processes to cycloheximide. Potassium uptake was greater from KNO3 than from KNO2 and in both instances it was enhanced during the early stages of the accelerated phase of anion uptake. Moreover, addition of NaNO3 to KNO2 substantially increased potassium uptake. A coupling between anion and potassium uptake was therefore evident, but the coupling was not obligatory because the accelerated phase of nitrite uptake could occur in absence of rapid potassium uptake. [ABSTRACT FROM AUTHOR]

Intact, 14‐day‐old nitrogen‐depleted wheat (Triticum vulgare cv. Blueboy) seedlings were exposed to solutions of 0.5 mM KNO2, 0.05 mM CaSO4 and 1 mM sodium 2‐[N‐morpholino]‐ethanesulfonate, pH 6.1. Nitrite uptake was determined from depletion of the ambient solution or from incorporation of 15N in the tissue. An initial nitrite uptake shoulder was followed by a relatively slow uptake rate which subsequently increased to a substantially greater rate. This accelerated phase was maintained through 24 h. Nitrite accumulated to a slight extent in the root tissues during the first few hours but declined to low values when the accelerated rate was fully developed, indicating an increase in nitrite reductase activity paralleling the increase in nitrite uptake capacity. About 50% of the nitrogen absorbed as nitrite was translocated to the shoots by 9–12 h. Development of the accelerated nitrite uptake rate was restricted in excised roots, in intact plants kept in darkness, by 400 μg puromycin ml−1 and by 1 mM L‐ethionine. When puromycin and L‐ethionine were added after the accelerated phase had been initiated, their effects were not as detrimental as when they were added at first exposure to KNO2. The two inhibitors restricted translocation more than uptake. The data indicate an involvement of protein synthesis and a requirement for movement of a substance from shoots to roots for maximal development of the accelerated nitrite uptake phase. A requirement for protein synthesis in the transport of soluble organic nitrogen from roots to shoots is also suggested. [ABSTRACT FROM AUTHOR]

Lipid composition of whole roots of wheat (Triticum vulgare Vill. cv. Svenno Spring Wheat) and oat (Avena sativa L. cv. Brighton) and of cell wall fractions, mitochondrial fractions and microsomal fractions of these roots were studied. Lipid composition depended upon the level of mineral nutrition. In wheat total phospholipids, phosphatidyl choline and sulfolipid content was highest in the roots grown at the higher salt concentration, while the reverse was true for oat roots. In both species glycolipid and sterol content was lower in the high salt roots, at the same time as higher proportions of them were built into the microsomal fraction. Phosphatidyl choline content of the wheat root membrane fractions increased with the salt level, while the opposite occurred in the oat roots. The phosphatidyl choline content may be correlated with the (Ca2+, Mg2+)‐stimulated ATPase activity. [ABSTRACT FROM AUTHOR]

Etiolated 6-day-old wheat (Triticum aestivum L. cv. Chris) seedlings were subjected to osmotic stress by an application of polyethylene glycol 12 h prior to the exposure to a continuous 72-h light period. The water potential of the primary leaf of stressed seedlings was between -9 and -14 throughout the light period. Stress impaired seedling growth, leaf unfolding, and the increase in leaf area. The imposed osmotic stress reduced total chlorophyll accumulation, particularly after 9 h light, suggesting that this is the approximate time period for the depletion of the protochlorophyll(ide) pool and the pool of an essential protochlorophyll(ide) precursor. The chlorophyll a/b ratio of extracts from stressed and non-stressed plants was the same during the 72-h greening period. Water deficit stress impaired carotenoid accumulation sooner than the impairment of chlorophyll production suggesting either a smaller carotenoid pool size of precursors or that the metabolic pathway of carotenoid pool size of precursors or that the metabolic pathway of carotenoid synthesis was more sensitive to stress. Shifts from the usual plastid pigment absorbance maxima were not observed in these studies. [ABSTRACT FROM AUTHOR]

The effect of abscisic acid on plant growth and survival during water deprivation was studied in barley and wheat seedlings. Under conditions of both limited and ample water supply, treatment with abscisic acid greatly reduced transpiration and, in addition, suppressed root growth. In water-deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water-use. In addition, the growth period and survival of water-deprived seedlings were markedly prolonged. In field trials, however, abscisic acid had no significant effect on water- deprived seedlings. Possible reasons for this lack of response are discussed. [ABSTRACT FROM AUTHOR]

Wheat seedlings (Triticum aestivum cv. Pacific Blue Stem) grown under continuous low‐level illumination were used to study the effects of pressure variation and its duration. Growth was determined by dry weights, leaf length, and types of secondary roots produced. Two sublethal shock pulses (1.41 and 2.82 kg cm −2) and three pressure duration intervals (0.1, 1.0 and 10.0 seconds) were studied. The results indicated a general overall reduction in growth associated with the shock pulse and that the pressure duration interval influenced the shock‐ growth response. The long pressure duration interval was found to be the most influential on shock pulse response. Present knowledge indicates that a pulse rise‐time of 1 ms and a pressure duration interval of at least 1.0 second affect plant growth at sublethal shock pulses, such that the growth response is linear or bi‐directional, depending on the magnitude of the shock pulses, and either linear or complex with respect to pressure duration interval for any shock pulse level. [ABSTRACT FROM AUTHOR]

Nitrate reductase activity was inhibited as a result of reduced soil moisture potentials or application of NaCl to nutrient solutions. The decrease in enzyme activity of wheat seedlings exposed to salinity, was found 24 hours after exposure to stress. The effect of stress on nitrate reductase was found in cell-free extracts as well as in vitro in assays of intact leaf sections. A recovery in enzyme activity was found after irrigation or after removal of seedlings from salinity. While relative water content of the leaves was restored within 3 hours after removal of stress, full recovery of enzyme activity occurred only after 24 hours. Cycloheximide and chloramphenicol suppressed the activity of nitrate reductase in non-stressed seedlings, but had no effect on the activity of plants exposed to salinity. However, during removal of stress, cycloheximide prevented completely the recovery of nitrate reductase, while chloramphenicol did not interfere with the recovery of the inhibited enzyme activity. It is concluded that a fraction of nitrate reductase may be located in the cytoplasm and lost activity during stress, probably due to inhibited protein synthesis. Another fraction which may be associated with chloroplasts, was inhibited by stress due to conformational changes or partial denaturation. [ABSTRACT FROM AUTHOR]

The pool size of protochlorophyllide in wheat leaves irradiated for 5 minutes to 6 hours was studied. Protochlorophyllide then accumulated in the dark, but the pool size of regenerated protochlorophyllide was considerably smaller in leaves irradiated for six horns than in leaves irradiated for 5 minutes. The decrease in pool size of regenerated protochlorophyllide was found to take place at the time when the chlorophyll formation had accelerated and reached the linear phase. The protochlorophyllide accumulated is the form with absorption maximum at 650 nm, which is phototransformed to chlorophyllide with maximum absorption at 684 nm, This species goes through the Shibata shift when formed even after 6 hours of irradiation. If leaves, irradiated for 1 or 6 hours, were fed with δ-amino-levulinic acid the protochlorophyllide synthesis was only 1.2 times faster in the leaves irradiated for 6 hours than in those irradiated for 1 hour. In the case of leaves fed with δ-amino-levulinic acid the absorption maximum of protochlorophyllide is at 636 nm and the absorption maximum of the chlorophyllide formed is at 672 nm. [ABSTRACT FROM AUTHOR]

Kharkov 22 M.C. winter wheat was grown continuously from seed under four temperature regimens; 2°C; 2°C then transferred to 20°C; 6°C, and 20°C. Plants were harvested at the 4‐leaf stage (except the 2°C plants which were harvested at the 3‐leaf stage) and the levels of endogenous gibberellins (GAs) were measured and their cold hardiness determined. The GA content of 20°C and the 6°C seedlings were about equal and greater (by 4‐ to 30‐fold) than the GA content of 2°C seedlings that had been transferred to 20°C (i.e. vernalized). The GA content of the 2°C seedlings was least of all, being 28‐ to 320‐fold less than the 20°C seedlings. At harvest the leaves of the 20°C seedlings were somewhat larger than those of the seedlings grown at 2°C and transferred to 20°C. The leaves of the 6°C seedlings were very much smaller and the leaves of the 2°C seedlings were smallest of all. It is concluded that while GAs may play a role in controlling leaf size and level of cold hardiness of wheat, they are not the most important factor. [ABSTRACT FROM AUTHOR]

Components of the initial uptake and active transport of rubidium were studied in potassium-starved and potassium-rich wheat plants. A metabolism-linked component of the initial uptake in the root was identified by means of DNP-treatment. It was shown that there is a direct proportionality between the magnitude of the metabolism-linked component of the initial uptake and the rate of active uptake. It is suggested that, in the free space, this metabolism-linked ion binding represents an initial step of the active ion transport preceding the subsequent carrier-mediated transport across the plasmalemma. [ABSTRACT FROM AUTHOR]

Leaves treated with δ-aminolevulinic acid accumulate protochlorophyllide636 in large amounts. Due to a continuous conversion of protochlorophyllide636 (nonphototransformable) into protochlorophyllide650 (phototransformable) in weak red light, the photoreduction of protochlorophyllide to chlorophyllide can proceed for at least 20 minutes and results in a chlorophyllide content of the leaves three times higher than that in untreated leaves. The half time for this chlorophyllide accumulation is 55 seconds. A photodestruction of the pigments takes place at high light intensities or if the content of protochlorophyllide636 is high. The conversion of protochlorophyllide636 to chlorophyllide is dependent on the light intensity used for phototransformation of protochlorophyllide650. The conversion of PChlide636 was not limiting for chlorophyllide formation within the range of the light intensity used. The extrapolation of a double reciprocal plot of chlorophyllide formation, rate versus light intensity gives a maximal value of 8.7 μg chlorophyllide per g fresh weight and min. The conversion of protochlorophyllide635 to protochlorophyllide650 is believed to depend on the available sites of an apophotoenzyme. [ABSTRACT FROM AUTHOR]

Citrate synthase of wheat (Triticum aestivum L.), bean (Phaseolus vulgaris L.), cauliflower (Brassica oleracea L.), and a marine blue-green alga (Coccochloris elabens) is inhibited by sulfhydryl binding reagents. The inhibitions are partially reversed by dithiothreitol. Pig heart citrate synthase is only slightly inhibited by the same reagents and this is completely reversed by dithiothreitol.. All citrate synthases in this study are inhibited by adenosine triphosphate. The inhibition is relieved by increasing the concentration of acetyl coenzyme A. Citrate synthase of wheat, cauliflower, bean, and pig heart was estimated by gel filtration to have a molecular weight of 100,000 daltons. The Coccochloris citrate synthase was estimated to have a molecular weight greater than 250,000 daltons. The evolutionary implications of these findings are discussed. [ABSTRACT FROM AUTHOR]

The characteristics of the uptake mechanism of chloride ions in citrus (Citrus spp.) were studied in excised, high-salt, roots as to the nature of the isotherm at a wide range of uptake durations and Cl- concentrations. In addition, the effects of metabolic inhibitors, low temperature and various treatments were studied, and compared with CI- uptake in excised roots of wheat (Triticum vulgare) under the same conditions. It was found that the uptake mechanism in excised roots of citrus differs considerably from that in wheat: (1) the rate of active uptake from 10 mM NaCI in citrus is 2.0 to 4.3 μmol CI- per g dry weight and h (vs. 35.5 μmol in wheat); (2) there is no saturation of the system even at high external concentrations (up to 90 mM), and uptake is continuous; (3) uptake in citrus is less sensitive to KCN and dinitrophenol. In addition, it was noted that the age of citrus seedlings and the initial chloride content of both citrus and wheat roots markedly affected CI-uptake. The data were analyzed in the light of the dual mechanism hypothesis of ion uptake, and it was concluded that only system 2 (high Km), is operating in the excised citrus roots studied. This is in accordance with the conditions prevailing in the field (whence the plant material was collected): high concentration of the soil solution in contact with the roots, and high salt status of the tissue, it is further suggested that the uptake of ions in citrus (and presumably in other perennial woody plants), is related to its growth habits and to the size and morphology of the root system. [ABSTRACT FROM AUTHOR]

Two methods for studying the role of stomata in controlling leaf water status are compared, using data for field grown spring wheat (Triticum aestivum L.). The first is based on comparisons of leaf water potential and stomatal conductance and their responses to different soil water treatments as obtained by irrigation or by placing plastic rainwater gutters between rows to remove a proportion of the incident rainfall. The second method exploits the varying potential evaporation and the consequent changing leaf water potential and stomatal conductance during the course of a day. Good stomatal control is indicated by large values of the ratio of the amount of variation in stomatal conductance to that of leaf water potential. A particular advantage of the latter method is that it does not require a range of soil water treatments, and it can therefore be more readily used to compare the degree of stomatal control in a range of genotypes. There was generally good agreement between the methods, with the second method showing greater sensitivity. Stomatal conductances were measured with a continuous flow diffusion porometer which had a thermostatically controlled leaf chamber. This feature had the advantage that conductances could be obtained directly from the output of the humidity sensor without the necessity for routine measurement of, and correction for, leaf temperature. [ABSTRACT FROM AUTHOR]

Contemporary Romanian agriculture synthesizes socialist theory and national goals through a diversified agricultural system emphasizing grain. Wheat is sown in all but the most unfavorable areas, and measures to reduce crop losses by drought and winterkill are the prime agricultural tasks. State agricultural enterprises play a leading role in the plan for increased, stable wheat harvests. Dragalina, a 7,306 hectare state agricultural enterprise comprised of seven farms and employing 250 full-time and 400 part-time employees, is an example of the Party's successes and failures in wheat. Wheat yields in 1972 were well below the enterprise potential, and the limiting factor was perceived to be quality of labor and incentive. Wheat in Romania reflects the Party's planned modification of traditional spatial patterns, socialist agricultural organization, and priorities. [ABSTRACT FROM AUTHOR]

Piericidin A and oxaloacetate have been used as inhibitors to investigate the operation and localisation of NAD+-linked dehydrogenases and the possible compartmentation of these enzymes within the matrix of the mitochondrion. 1. Mitochondria isolated from etiolated shoots of wheat (Triticum vulgare) were shown to oxidise a variety of NAD+-linked substrates. Oxaloacetate, when added to rapidly respiring preparations (i.e. state 3) resulted in a large but transient inhibition of the oxidation of both pyruvate and citrate, but had little effect on the rate of oxidation of malate. 2. The products of oxidation of malate, in the absence of added NAD+, were found to be a large quantity of pyruvate together with smaller quantities of oxaloacetate and citrate. Using potassium ferricyanide as a non-penetrating electron acceptor it was possible to show that the malate oxidation occurred in the matrix. This is consistent with the operation of both the malic enzyme and a low level of malate dehydrogenase within the matrix of the mitochondrion. 3. The low level of inhibition of malate oxidation by oxaloacetate was a function of the concentration of malate and appeared to be of a competitive nature. 4. Measurement of the redox state of the endogenous NAD+ pool showed that under phosphorylatig conditions both malate and citrate reduce approximately 15% of the total coenzyme. The addition of 0.2 mM oxaloacetate to phosphorylating aerobic mitochondria failed to oxidise any of the NAD+ reduced by malate but resulted in a partial oxidation of NAD+ reduced by citrate. The transition from the aerobic to anaerobic state in the presence of malate resulted in a biphasic reduction of the endogenous NAD+, whereas in the presence of citrate it was monophasic. 5. The oxidation of NAD+-linked subtrates, including malate, was found to be only partially inhibited by piercidin A. The piericidin-A-resistant pathway was found to be located internally on the basis of experiments using ferricyanide as a non-penetrating electron accepter. The first site of phosphorylation was not coupled to oxidation mediated by the piericidin-A-resistant pathway. 6. The presence of piericidin A altered the shape of the malate saturation curve. In the absence of the inhibitor it was found to be biphasic; saturating at 60 mM and in its presence to be monophasic saturing at 15 mM. At high concentrations of malate (60 mM) piericidin A caused approximately a 30% inhibition, similar to that found with other NAD+-linked substrates, while at lower concentrations of malate (15 mM) piericidin A caused a much higher inhibition (80%), which subsequently recovered to the much higher piericidin-A-resistant rate observed with higher concentrations of malate. 7. In the presence of piericidin A oxaloacetate caused severe but transient inhibition of malate oxidation, similar in magnitude to that observed during pyruvate oxidation in the absence of piericidin A. 8. It was concluded that the data were consistent with the spatial separation of both the internal malic enzyme and malate dehydrogenase together with the internally located piericidin-A-sensitive and resistent electron-transport pathways. [ABSTRACT FROM AUTHOR]

In 1973, 103-108 adults of the Colorado beetle, Leptinotarsa decemlineata (Say), were found, of which 51 were alive. This is the largest annual total for 20 years. Details of these finds are presented. The outstanding feature is the large number (74-79) associated with French wheat. [ABSTRACT FROM AUTHOR]

Pot-grown plants of spring wheat, cultivar Maris Dove, Were subjected, commencing at ear emergence, to different, constant levels of infestation by Metopolophium dirhodum (Wlk.) in a glasshouse. Infestation with six aphids per stem over 11 days had no significant effect on yield. Infestations with either six or 50 adult aphids or their equivalents, when maintained until ripening, resulted in lower yields of both grain and straw dry matter. Loss of grain was due to reduction in both 1,000 grain weight and the average number of grains per fertile spikelet. Harvested dry matter content of leaf blades was unaffected by infestation, but the dry matter, content of stems was reduced in infested plants. In breeding aphid-resistant cereals for Britain, resistance characters restricting aphid multiplication are most likely to reduce yield losses due to aphid attack. [ABSTRACT FROM AUTHOR]

Foliar sprays of fungicides were evaluated in a field where winter wheat cv. Joss Cambier was subject to a severe natural infection of yellow rust (Puccinia striiformis Westend.). Almost complete freedom from the disease was achieved on the leaves from repeated applications of BAS 3170F. This material prevented the development of appreciable disease for up to four weeks after spraying. Other chemicals gave varying degrees of protection but most lacked persistence. Control of ear infection was less satisfactory. The untreated crop, which was heavily attacked by yellow rust, showed a yield reduction of 34 per cent compared with the crop receiving greatest protection. The relationship between yield and yellow rust at growth stage 11.1 was statistically significant; the loss of yield recorded was 0.022 t/ha for each one per cent increase in the level of yellow rust on the flag leaf. [ABSTRACT FROM AUTHOR]

Data comparing the amount of infestation in eastern England on wheat, barley and oats by saddle gall midge are given for the years from 1967 to 1972. The level of infestation decreased in 1971 and 1972. The changes in the numbers of overwintering larvae in several fields, with their cropping, are recorded. In 1971 and 1972 the first adult was trapped on 18 and 19 May respectively; the peak flights occurred on 31 May 1971 and on 11 June 1972. It was not possible to obtain an overall relationship between the amount of galling and yield. It is suggested that the individual effects of the many factors which can affect yield can only be assessed from detailed experiments. In a small-scale trial in 1972, a fenitrothion spray applied in June prevented galling of barley. [ABSTRACT FROM AUTHOR]

This article reports on an empirical investigation of the impact of agricultural policy on the acreage-supply response of wheat. One of the important purposes of the commodity programs governing wheat has been to raise incomes to wheat growers. Since 1934 the federal government has employed a number of alternative programs to accomplish this end. Relying on the sharply inelastic demand for wheat, the programs have attempted to reduce wheat acreage below that which would be planted in a free market and, thereby, to raise prices sufficiently to insure larger gross and net incomes to wheat growers. In the study conducted an econometric model for the period 1934 to 1968 is developed and estimated using annual time-series data. The study conducted concludes that agricultural programs have exerted a significant influence on the amount of wheat acreage planted since 1933. This result is especially pronounced over the period 1954-70. The study conducted also elaborates that planted wheat acreage has been responsive to the loan level, the acreage allotment, direct payments, acreage reserve payment rates, and to a lesser extent, the soil banks conservation reserve program. It also remarked that lagged market price has not been an important determinant in the acreage planted to wheat.

A quantitative assessment of the "green revolution" associated with Mexican varieties of wheat in the Indian Punjab is attempted as alternative to the usual impressionistic assessments. Results indicate that the technical change has been cost-saving and has not been strongly biased in either a labor-saving or a capital-saving direction. Wheat production experienced a favorable cost curve shift on the order of about 16 percent. Input demands per acre increased by about 25 percent. Increased capitalized land values lead to inferences about income distribution and constitute a source for reinvestments designed to maintain the momentum of the "green revolution." [ABSTRACT FROM AUTHOR]

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article explores the relative efficiency of wheat production in the Indian Punjab. In recent contributions to this research review, Lawrence Lau and Pan Yotopoulos applied the profit function concept to the analysis of relative efficiency of Indian agriculture. They developed an operational model to measure and compare economic efficiency and its components of technical efficiency and price efficiency for groups of firms. There are two conclusions that follow the analysis of data. First, there seem to be limited possibilities for growth by improving allocative efficiency in moving toward production frontiers. Second, the researcher finds that tractor-operated wheat farms are no better off in terms of their economic performance than non-tractor-operated farms and that large farms are no better off than small farms.

In a recent article in this journal of The Review of Economics and Statistics, Franklin Fisher and Peter Temin reported their estimates of wheat supply functions for selected states in the U.S. from 1867 to 1914. A comment by R. Higgs together with a reply from Fisher and Temin appeared in a later number. The author of this article wishes to add to this literature by making the following points, first, Fisher and Temin were in error in defending themselves against Higgs by arguing that spring wheat dominated throughout most of the period; second, even if the specification problem raised by Higgs did not vitiate meaningful interpretation of their price-elasticity estimates, their conclusions regarding productivity trends in wheat regions are really not supported by their own findings. The Fisher and Temin response to Higgs is inadequate. Other price data are available from local and state sources for much, if not all, of this period. Further, their assertion related to the price of winter wheat is an expedient one, but it does not change the fact that their supply function is misspecified.

Se presentan noticias que tratan de la economía de los Estados Unidos. Se informa que Brasil quería reducir sus importaciones de trigo norteamericano. La Comisión Arancelaria de los EE. UU. habló acerca de la importación de plomo y cine. Se presentan cuadros estadísticos con información sobre la distribución de las reservas monetarias en el mundo y las reservas monetarias como porcentaje del comercio exterior.

Microsomal fractions from wheat (Triticum vulgare) and oat (Avena sativa) roots were used to study Mg2+ and Ca2+ activated adenosine triphosphatases, their dependence of pH, and how Mg2+ and Ca2+ compete or add in stimulation and inhibition. Wheat gives a high proportion of Ca2+ stimulated ATPase. Less effect is obtained with Mg2+. The characteristics of oat ATPase are the reverse. The ATPase from the wheat roots depends on the mineral nutrition. A kinetic analysis shows one site, where Mg2+ and Ca2+ at low concentrations (or complexes between the divalents and ATP) cooperate in the activation of the ATPase. The action of this site is more clearly expressed at pH 6.0 than at 6.8, and more clearly in the preparations from low salt roots than in those from high salt conditions. In another site, which is particularly evident in preparations from high salt roots tested at pH 6.8, high concentrations of Mg2+ inhibit the ATPase; this inhibition is competitively relieved by Ca2+ The specific activity of the ATPase from high salt roots of wheat is higher than that from low salt roots, although the amount of protein of the fraction studied remains the same, when calculated per g fresh weight of the roots. [ABSTRACT FROM AUTHOR]

Thermosensitivity was induced through a heat shock in wheat roots. Chloramphenicol and ethanol decreased the induced sensitivity to a degree where all roots were alive. The heat sensitized wheat roots were more sensitive to high salt concentrations than untreated roots. [ABSTRACT FROM AUTHOR]

Various plant species were placed in a 13.5 liter belljar equipped with a motor-driven fan directly above the plants. Air was continually circulated from the belljar through an infrared CO2 analyzer at the rate of 1.5 1/min. Species tested included Triticum aestivum, Hordeum vulgare, Avena sativa, Zea mays, Sorghum vulgare, Phaseolus vulgaris, Glycine max, Pisurn sativum, and Magnolia grandiflora. Increases in respiration of shoots or intact plants were detected at windspeeds of 3.6 m/s and above. All species responded in a similar fashion with increases in respiration of 20 to 40 0/0 being typical at a windspeed of 7.2 m/s which is similar to windspeeds under many natural conditions. The respiration rate returned to the initial rate within a short time after the wind had stopped. In Magnolia a sustained elevated respiration rate was measured over an exposure period of 3 hours to a wind velocity of 7.1 m/s. In some experiments flutter of the leaves was prevented but the respiration rate of bean and Magnolia was still elevated in the wind. This would suggest that the response is subcellular and not due to gross movement of the leaf itself. It is suggested that such an elevated respiration rate (maximum increase measured was 56 %) might be expected to interfere with net assimilation and may be responsible for lower yields obtained in windy regions. [ABSTRACT FROM AUTHOR]

Uptake, translocation and metabolism of 14C-labelled 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2,4-dichlorophenoxyacetic acid (2,4-D) in seedlings of wheat (Triticum aestivum L.) were studied. The uptake of the herbicides through the upper surface of the first leaf was slow but was almost complete after nine days. Picloram was absorbed faster than 2,4-D. Picloram was also translocated into the stem and the untreated leaves to a greater extent than 2,4-D. Only small fractions of the activity were recovered from the roots and from the nutrient solution. Picloram and 2,4-D formed water-soluble conjugates in the tissues. These conjugates were very labile and hydrolyzed under release of the unchanged herbicides. The isotope from 2,4-D was also incorporated in an insoluble fraction, containing cell walls and proteins. Also few this fraction biologically active 2,4-D could be released by hydrolysis. The formation of the complexes was partly prevented by cycloheximide. It is suggested that herbicide detoxification through complex formation is of importance for the relatively low sensitivity of wheat to auxin herbicides. [ABSTRACT FROM AUTHOR]

The investigation concerns the influence of potassium on the transpiration rate of Triticum aestivum and Pisum sativum grown in nutrient solutions. Plants with high amounts of potassium were found to have the lowest transpiration rates. Shoot/root ratio, stomatal frequency, and stomatal aperture were correlated with the potassium concentration in the leaves. In Triticum no correlations with leaf concentration of Na were evident. Short term experiments were carried out in order to investigate the effects on the transpiration rate of a sudden increase in potassium concentration in the nutrient solution. An addition of potassium chloride to potassium deficient wheat plants resulted in a decrease in the transpiration rate of up to 50 % within two hours. Comparative tests with sodium chloride resulted in a decrease in transpiration rate of the same magnitude, indicating that the short-time reaction is not specific to potassium. The experiments show that the transpiration rate can be regulated by varied potassium and sodium concentrations. The observed effect is supposed to be due to changes in the stomatal aperture. [ABSTRACT FROM AUTHOR]

White light increases the inhibition of growth in length of pea seedling roots caused by 2,4-D. This effect is most pronounced in the case of lateral root growth. The effect is obtained also if the shoots above the coryledons are removed and is probably due to the direct influence of light on the roots. While light also weakly enhances the inhibition of pea root growth caused by 1-naphthylacetic acid, light does not increase the sensitivity of wheat roots to 2,4-D or naphthylacetic acid. [ABSTRACT FROM AUTHOR]

Supplying nitrate to N-depleted wheat seedlings (Triticum vulgare cv. Knox) stimulated the uptake and translocation of both 85Sr and 45Ca. Since the increase in 45Ca accumulation was greater , the 85Sr/45Ca ratio in the exchangeable fraction on the root tissue and translocation to shoots. The increase in percent transported to shoots occurred largely in the period of most rapid nitrate uptake. A split root study indicated that nitrate was ineffective when it was supplied to a different portion of the root system than that exposed to 85Sr and 45Ca. Nevertheless, ammonium and urea also increased the translocation of the two cations , indicating that the effects of nitrate could not entirely be ascribed to a direct of the nitrate anion. [ABSTRACT FROM AUTHOR]

The effect of coumarin, IAA, ethylene, kinetin and gibberellic acid on roots of maize and wheat was investigated. Sterile attached and detached roots and isolated elongation zones were used. In some experiments a semi-sterile procedure was followed. The effects of the different regulators separately or in various combinations together with coumarin were studied on the root growth with regard to division, elongation and swelling of the cells, The ethylene production in isolated elongation zones was measured after treatment with coumarin, IAA, PCIB, kinetin, colchicine and dinitrophenol. The results show the following: 1) Each substance produces a specific morphologic pattern. 2) Changes in polarity were demonstrated for auxin-induced swelling in cell divisions and cell expansion and for coumarin-induced swelling in cell division. Other cell expansion in swollen parts was due to cylindric cells increasing in width while retaining their cylindric form. 3) Coumarin-induced inhibition could not be counteracted by IAA, PCIB, carbon dioxide, kinetin, gibberellic acid or Cycocel. 4) The ethylene production in isolated elongation zones increases noticeably after kinetin treatment, less strongly after auxin treatment and least after coumarin treatment. The production of ethylene does not seem to be correlated with the morphogenetic effect of the different substances. 5) The isolated elongation zones reacted to a) IAA and kinetin with an increase in length in some cases and b) gibberellic acid with a reduction of their width. 6) The inhibitory effect of coumarin on the growth in length of the elongation zones was diminished by kinetin. The swelling produced by coumarin in these zones was reduced by gibberellin acid. The effects just mentioned of kinetin and gibberellic acid. The effects just mentioned of kinetin and gibberellic acid were considered as indirect ones. — From the present finding it was concluding that concomitant effects of auxin, ethylene, cytokinins and gibberellins are not obligatory are not obligatory for coumarin to exert its morphogenetic effects on root growth. In discussing the results some pitfalls in studies of growth reactions after application of hormones to roots containing meristem were emphasized. [ABSTRACT FROM AUTHOR]

The oxygen exchange obtained when isolated chloroplasts of wheat are irradiated, without the addition of a Hill oxidant, has been investigated. Depending on the wavelength, two types of oxygen exchange are obtained. In light absorbed by both photosystems an oxygen gush appears directly upon irradiation. This oxygen evolving reaction is soon replaced by an oxygen, uptake which is present until the end of the irradiation period. In light absorbed mainly in photosystem I, no oxygen gush can be observed, instead an oxygen uptake appears directly upon irradiation. An oxygen evolving process can also be observed in irradiations performed with photosystem I light, but this process appears after 10-15 seconds of irradiations. The influence of various external factors on the oxygen gush and the oxygen uptake, e.g. different wavelengths, light intensity, length of the dark periods between irradiations, was studied. The results show that the oxygen evolving reaction appearing upon irradiation with light absorbed by photosystem II and I, reflect the reduction of an oxidant, probably plastoquinone, in the electron transport chain between the two photosystems. The reoxidation of this oxidant can be brought after irradiating with light absorbed in photosystem I, or by prolonging the dark period between irradiations, or through some unknown process connected to photosystem II. The oxygen uptake which consists of two components, one appearing directly upon irradiation and the other one appearing after about 10 seconds of irradiation, confirms earlier observations that oxygen can be reduced in photosystems. The electrons for the oxygen uptake appearing directly upon irradiation, are obtained from the reduced intermediates in the electron transport chain between the two photosystems. The electrons for the other oxygen uptake process are obtained from a reductant in the chloroplasts with access to the carrier chain between the photosystems. Whether the two oxygen uptake reactions reflect two sites of interaction of oxygen with the electron transport chain or only one site is discussed. [ABSTRACT FROM AUTHOR]

A study has been made of tissue tensions in growing Triticum roots. After the initial phase of elongation with both a lateral and an exponential longitudinal growth, the tissues are under strong longitudinal stress. Plasmolysis in situ or splitting of the root in the pericyclic region causes an increase in length of the perivascular part. Freed from the stele the perivascular part contracts on plasmolysis. During the following only longitudinal growth, the stress decreases under decreased root diameter. When elongation has ceased, the root in situ contracts on plasmolysis. It is suggested that during radial growth longitudinal stresses are built up, which are released when the stele catches up with the growth of the cortex. The similarity to conditions in contractile roots of Arum (Lamant and Heller 1967) is pointed out. A difference is found in the polarity of growth and thus in the mode of release of the stresses. The cause of the tensions and methodical difficulties are discussed. [ABSTRACT FROM AUTHOR]

Seedlings of Triticum aestivum L. were sprayed with menadiol disulfate in water solution. Eight days after spraying, the content of phylloquinone in the shoots was more than twice as high as in shoots of untreated control plants. The application of menadiol disulfate caused a stimulation of the synthesis of phylloquinone. It is possible that menadiol is an intermediate in the biosynthesis of phylloquinone. [ABSTRACT FROM AUTHOR]

The content of adenosine triphosphate (ATP) in roots of wheat (Triticum aestivum L.) was determined with the firefly-luciferase method. The content is decreased by D-mannose, which inhibits root growth, respiration and chloride uptake. In intact seedlings the inhibition of root growth is relieved by other sugars and also by the flavanone naringenin and by 2,4-dinitrophenol. This reversal is combined with an increased content of ATP. The inhibition of chloride uptake by mannose in excised roots is reversed by some other sugars (including D-galactose which is in itself inhibitory to root growth), and also in this case the ATP content is increased. Naringenin and dinitrophenol do not relieve the inhibition of chloride uptake caused by mannose. Nor do they increase the content of ATP in this case. The primary effect of mannose seems to be inhibition of glycolysis whereas the effect upon root growth is secondary. Galactose, which also inhibits root growth, does not inhibit respiration or reduce the ATP content and the primary effect of galactose (and also of 2-deoxy-D-glucose and 2-deoxy-D-galactose) seems to be on the synthesis of cell wall substances. [ABSTRACT FROM AUTHOR]

The geotropic orientation of seminal roots of wheat has been studied on seedlings grown in five different positions, stationary and on clinostats. The roots perceive a geoinduction before they have emerged from the grain and perform curvatures inside the grain. These are very sharp and transient, the following root growth is straight in any direction unless the positions are shifted. The roots are insensitive to a static gravi-induction but react to a change in gravitation with a geotropic curvature in positive direction. The roots may not reach or reach, or even pass the plumb-line. The orientation of a root depends upon the direction of its initiation and the geotropic curvature attained before the reaction has ceased. There is no nastic component in the reactions. The 'plagiotropic' orientation is explained by the limited positive reaction followed by an ageotropic state. Main root and adventitious roots react in the same way. Reactions to later stimuli give likewise limited curvatures which are weaker but of longer duration. - The effect of temperatures from 10°C to 25°C has been studied and compared to the temperature effect on cell elongation. It is concluded that the whole reaction may be explained by the regular auxin effects on cell elongation. No other hormone should be required and no plagiotropic mechanism is necessary. [ABSTRACT FROM AUTHOR]

A portable freezing point meter was used in the field to measure the water potential gradients in sunflower (Helianthus annuus), beans (Phaseolus vulgaris), corn (Zea mays), wheat (Triticum aestivum), pumpkin (Cucurbita pepo), potato (Solanum tuberosum), alfalfa (Medicago sativa), and sugarbeets (Beta vulgaris). The measurements were made between daybreak and sunrise, and again during the middle of the afternoon on days when the potential evapotranspiration varied between 6.5 and 8.0 mm of water. The gradients varied from a maximum of 0.2 bar per cm in a wheat, down to an undetectable value for pumpkin. Although most of the soil in the root zone was kept at potentials above –1 bar, the bulk of the root tissue had water potentials of –5 to –10 bars. Differences in water potential between shaded and unshaded leaves, and between leaf tissue and guttation fluid suggested a similar drop of several bars between xylem elements and the surrounding leaf tissue in some plant species. The implications of such drops are discussed with respect to plant water transport equations and pressure cell potential measurements. [ABSTRACT FROM AUTHOR]

The growth of wheat seedling (Triticum sativum) is inhibited by abscisic acid (ABA). The inhibition increases with the concentration of ABA (from 10-6M to 5 × 10-5M) and is stronger in the case of coleoptiles and first leaves than in roots. In contrast, naphthaleneacetic acid (ANA), at 10-5M, exerts its greatest inhibitory effect on the roots. The inhibitory effect of ABA on coleoptiles can be partially overcome by kinetin and to a much smaller degree by gibberellic acid. Neither of these two compounds, at 10-5M, had any effect on the ABA-induced inhibition of root growth. The RNA and DNA contents per plant organ are considerably reduced after treatment of the seedlings with ABA, particularly in the coleoptiles and the first leaves. The incorporation of uracil-2-14C and uridine T (G) into RNA of treated seedlings is reduced in the case of coleoptiles and first leaves, but considerably enhanced in roots. The mechanism of the action of ABA is discussed in the light of these results. [ABSTRACT FROM AUTHOR]

Excised wheat roots in culture release a substance inhibitory to their growth and which can be absorbed on activated charcoal. This growth inhibitor can be isolated in pure form by diethylether extraction followed by DEAE cellulose and thin-layer chromatography. At very low concentration it inhibits lateral root development. The significance of this inhibitor to the problem of the continuous growth of cultured wheat roots is discussed. [ABSTRACT FROM AUTHOR]

The major ether-soluble, growth-stimulating substance detected by the Avena coleoptile straight-growth test in extract from sprouting buds of Scots pine (pinus silvestris L.) was identified as indole-3-acetic acid by Rf values in 5 solvent systems and by its elution volume in ethanol on a Sephadex LH-20 column. When the substance was applied to the growth solution of wheat roots in a special test the growth in length of the roots was at first inhibited, but growth was recovered after about 6 hours in the same manner as when small quantities of IAA were applied. The extracts also contained large amounts of growth inhibitors which interfered with the auxin response if they were not removed. [ABSTRACT FROM AUTHOR]

The purpose of this article is to review briefly the international situation of wheat, and to describe and analyze a new world-wide commodity arrangement which the author feels has both geographic significance and a fair chance for success, the International Wheat Agreement (IWA) of 1949. Economists and geographers have frequently pointed out how commodity controls on the international level have failed in the long run, either because some of the actual or potential surplus countries were unrepresented in the agreement, or because artificially high prices forced the consumer to seek substitute sources of supply or even substitute commodities. In essence, the IWA may be explained as a multilateral bulk-purchase contract, under which the signatory exporting countries guarantee to supply the signatory importing countries as a group specified quantities of wheat during the four-year life of the Agreement at a price not to exceed a fixed maximum per bushel. Exporting countries are urged to maintain their wheat stocks at such levels that they are not likely to be unable to meet their export commitments in the case of a bad crop year. Practically all of the important wheat-importing countries have joined the Agreement but, based on their past trade records, many of them are likely to buy excess of their guaranteed import quantities.