32P Uptake Research Articles

Antagonism of fluoride toxicity by high levels of calcium but not of inorganic phosphate during secretory amelogenesis in the hamster tooth germ in vitro

Whether the interference by fluoride (F −) with secretory amelogenesis in vitro could be modulated by altering the levels of calcium (Ca) and inorganic phosphate (P) in the medium was investigated. Hamster first upper molar tooth germs in the secretory phase of amelogenesis were exposed to 10 μM–1.31 mM (0.2–25 parts/10 6) of F − in vitro for 2 days in the presence of either low (1.2 mM), moderate (2.1 mM) or high (4.1 mM) levels of Ca, or moderate (1.6 mM) and high (3.6 mM) levels of P. The biosynthesis and secretion of enamel matrix proteins under each of the experimental conditions were examined by labelling with [ 3H]-proline during the last 24 h of culture, and mineralization by labelling with 45Ca and [ 32P]- orthophosphate. With moderate levels of Ca and P (control medium), F − increased the uptake of 45Ca and 32P in a dose-dependent manner; F − did not inhibit the synthesis of matrix proteins but to a moderate extent impaired their secretion. In explants grown in the presence of 52 μM of F − the superficial layers of enamel matrix deposited in vitro (fluorotic matrix) failed to mineralize. Increasing P levels in the medium had no clear histological effect, whereas lowering Ca levels sometimes seemed to aggravate the F − effect. Raising Ca levels improved the histological pattern: in spite of the presence of F −, high Ca levels allowed a limited mineralization of the superficial layer of fluorotic matrix along with a strong rise in mineralization of the deeper layers of pre-exposure enamel. High Ca levels also considerably reduced the cellular changes in secretory ameloblasts induced by 52 μM of F − and slightly counteracted the inhibition of matrix secretion, as measured biochemically. Some of the effects of F − on secretory amelogenesis in vitro can thus be reversed by raising Ca levels in the medium. Therefore, the effect of F − on secretory amelogenesis in vitro seems to be primarily interference with the enamel mineralization process per se and, secondarily, an impairment of matrix secretion.

Use of actin-bound adenosine 5′-diphosphate as a method to determine the specific 32P-radioactivity of the γ-phosphoryl group of adenosine 5′-triphosphate in a highly compartmentalized cell, the platelet

Determination of the specific 32P-radioactivity of cytoplasmic ATP in 32P- P i-labeled platelets is complicated by the presence of a large pool of metabolically inactive, granule-stored nucleotides. Moreover, our data show that the specific 32P-radioactivity of cytoplasmic ATP is severely underestimated when determined in platelets after the complete secretion of granule-stored nucleotides, possibly due to isotopic dilution with granule-stored phosphate. As F-actin-bound ADP is ethanol-insoluble, this pool can be readily separated from the other nucleotide pools in platelets. Here we show that the specific 32P-radioactivity of F-actin-bound ADP accurately reflects that of the γ-phosphoryl group of cytoplasmic ATP. During uptake of 32P- P i by human platelets the specific 32P-radioactivity of F-actin-bound ADP equals that of the monoester phosphates of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate, which are in metabolic equilibrium with cytoplasmic ATP. Therefore, this method enables the determination of the specific 32P-radioactivity of the γ-phosphoryl group of cytoplasmic ATP in platelets even under short-term labeling conditions.

Early effects of escherichia coli endotoxin infusion on vasopressin-stimulated breakdown and metabolism of inositol lipids in rat hepatocytes

The turnover of vasopressin-stimulated 32P-phosphoinositides and 32P-phosphatidic acid and accumulation of [2-3H]-inositol phosphates were examined in hepatocytes from rats infused i.v. with saline and E. coli endotoxin for 3 hrs. Within 60s of VP stimulation the decrease in phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate labeling as well as the increased uptake of 32P into phosphatidic acid were similar in both groups. However, at a later time (300s) the 32P-phosphatidylinositol turnover was greatly decreased concomitantly with a higher labeling of phosphatidic acid. The accumulation of [2-3H]-inositol phosphates in ET-cells was significantly decreased both at 30s and 600s after VP addition. The distribution of [2-3H]-inositol labeling accumulated in the different inositol phosphate fractions over the first 30s of VP stimulation showed a tendency to lower accumulation of inositol trisphosphate, and a significantly lower accumulation of inositol bisphosphate simultaneously with a higher labeling of the inositol tetrakisphosphate fraction. These observations reflect an early effect of ET-infusion on VP-stimulated inositol lipid turnover and on the subsequent metabolism of the released inositol phosphates.

Uptake and transport of shell minerals in Glottidia pyramidata Stimpson (Brachiopoda: Inarticulata)

Uptake and transport of shell mineral ions have been investigated in the lingulid brachiopod Glottidia pyramidata Stimpson by tracer techniques and histochemical methods at the ultrastructural level. 45Ca autoradiography as well as 45Ca uptake studies show that Ca ions are taken up from the seawater medium primarily by the iophophore and then move through the coelomic system into the mantle and eventually are deposited in the inner shell layer. The rate of Ca deposition in the apatite shell is 12 × 10 −2 μg· mg −1 shell weight ·h −1, which is similar to that in the calcite shell of the bivalve Argopecten. Potassium antimonate staining for Ca, X-ray microanalysis and electron diffraction analysis further suggest that Ca along with inorganic phosphate are deposited in large vacuoles in the mantle epithelium to form granules of a mixture of apatite crystals and sometimes of amorphous materials. These granules serve as reservoirs of shell minerals. In contrast to 45Ca, 32P uptake from seawater is lower in the shell than in other parts of the animal. Therefore, the major source of inorganic phosphate for Glottidia shell formation is unlikely to be the seawater.

Relative uptake of32P by cassava, banana, elephant foot yam and groundnut in intercropping systems

Absorption of applied32P by the treated as well as neighbouring plants in two- and three-crop intercropping systems involving cassava (Manihot esculenta Crantz), banana (Musa (AAB) ‘Mysore’), elephant foot yam (Amorphophallus campanulatus Blume) and groundnut (Arachis hypogaea L.) was studied in field trials. Radiophosphorus applied to the root zone of one of the component species in the mixed systems was found to be absorbed not only by the treated plant but also by the neighbouring plants. Banana was the most dominant species in the cassava-banana-elephant foot yam intercropping system and accumulated the major portion of the radioactivity recovered in the whole system. Cassava planted on raised mounds absorbed32P from the root zones of elephant foot yam and banana growing in the interspaces. Absorption of32P from cassava mounds by elephant foot yam was negligible.

In vivo ovarian uptake and processing of vitellogenin in the rainbow trout, Salmo gairdneri

AbstractThe in vivo uptake and processing of vitellogenin (VTG) into developing oocytes of rainbow trout were studied. Oestrogenized trout injected with 32P and 3H‐leucine incorporated these labels into newly synthesized vitellogenin. This dual‐labelled VTG was purified from the serum and injected intraperitoneally into sexually maturing female trout. The 32P. 3H‐VTG was readily taken up from the peritoneal cavity into the blood, without degradation, and thus became available for sequestration by developing oocytes. Ovarian uptake of 32P. 3H‐VTG was very rapid. Eight h after injection, approximately half of the labelled VTG was in the blood, but this figure had fallen to 12% after 48 h, and to 0.2% after 2 weeks. This fall in blood 32P. 32H‐VTG level coincided with increases in the level of both radiolabels in the ovary. Eight hours post‐injection, a significant amount of 32P. 32H‐VTG was found in the ovary homogenate. Most of this material was intact, primarily representing VTG bound to the follicle surface. However, small amounts were contained within the follicles and probably represented newly sequestered VTG which had not yet been degraded into the yolk proteins, lipovitellin and phosvitin. Twenty‐four hours post‐injection, approximately 25% of the injected 32P. 3H‐VTG had been sequestered by the ovary. Although a small proportion of the labels were associated with intact VTG, the majority of the 3H and 32P eluted with lipovitellin and phosvitin, respectively, the yolk proteins derived from VTG. After 2 weeks, nearly 70% of the 32P. 3H‐VTG initially injected had been incorporated into the ovaries, all of which was present as labelled yolk proteins. The rate of uptake of VTG was highest in the fish with the largest follicles, where it approached 120 ng.mm2 follicle surface h−1. The results demonstrate that both the uptake and processing of VTG by trout oocytes are rapid features that are reflected in the rate of ovary growth seen during exogenous vitellogenesis.

The effect of ethanol on phospholipid metabolism in rat pancreas

The phospholipid effect involves agonist-induced breakdown of phosphatidyl inositol (or polyinositides) generating second messengers followed by increased incorporation of P 32 during the resynthetic phase of the cycle. Ethanol, an aetiological factor in pancreatitis, has been shown to have various effects on pancreatic secretion. In this study ethanol decreased the incorporation of P 32 into phosphatidyl inositol but had no effect on the stimulated breakdown of prelabelled phosphatidyl inositol. However, in addition to recycling of phosphatidyl inositol stimulation of pancreatic tissue results in increased incorporation of precursors into other phospholipids. Cholecystokinin increased the incorporation of both [U- 14C] glucose and P 32 into phosphatidyl ethanolamine 3-fold but had no effect on P 32 incorporation into phosphatidyl choline. As well as increased incorporation of P 32 into phosphatidyl inositol (8-fold) Cholecystokinin also increased the incorporation of [U- 14C] glucose into phosphatidyl inositol (4–5-fold) implying significant de novo synthesis of 1,2 diacyl glycerol in addition to the currently accepted recycling of the 1,2 diacyl glycerol back to phosphatidyl inositol. Ethanol caused an inhibition of P 32 incorporation into total phospholipid of rat pancreas during basal and stimulated conditions. When individual phospholipids were separated ethanol was found to decrease the incorporation of P 32 into phosphatidyl choline under basal conditions and into all phospholipids during Cholecystokinin stimulation. With [U- 14C] glucose as the precursor, ethanol inhibited its incorporation into phosphatidyl choline only. Ethanol did not alter the total P 32 radioactivity in the aqueous phase of the pancreatic extract nor the percent incorporated into nucleotides. This excluded decreased uptake of 32P and incorporation into nucleotides as a mechanism for the differential inhibition of P 32 versus [U- 14C] glucose incorporation into phospholipids other than phosphatidyl choline under stimulated conditions.

Effects of soil microorganisms on mycorrhizal contribution to growth of big bluestem grass in non-sterile soil

Plant dry weight and mycorrhizal root colonization of big bluestem ( Andropogon gerardii Vitman) inoculated with Glomus etunicatum Becker and Gerd. were suppressed if non-sterile prairie soil sievings or filtrate were added to pasteurized soil. Addition of prairie soil microorganisms, isolated onto peptone yeast extract, King's B, or starch casein agar media, to pasteurized soil also reduced dry weight and mycorrhizal root colonization of big bluestem inoculated with G. etunicatum. In contrast, addition of non-sterile soil sievings or filtrate or organisms isolated onto potato dextrose or pseudomonas isolation agar to pasteurized soil improved growth of non-mycorrhizal big bluestem. These effects of soil micro-organisms on plant growth were further quantified by comparing 32P uptake by fungicide treated and untreated mycorrhizal plants and by non-mycorrhizal plants in pasteurized and non-sterile soil. Mycorrhizal plants grown in pasteurized soil absorbed ≅10 times more 32P than mycorrhizal plants grown in non-sterile soil. Application of propiconazole (Tilt) or fenarimol (Rubigan), fungicides which inhibit 32P uptake by mycorrhizas, resulted in approx. 40- and 5-fold reductions in 32P uptake in pasteurized and non-sterile soil, respectively. Thus, more 32P is absorbed in pasteurized than in non-sterile soil, probably because soil microorganisms limit mycorrhizal activity in non-sterile soil. Assessments of mycorrhizal contribution to plant growth conducted in sterilized soils may significantly overestimate the effects of VAM fungi because other soil microorganisms are not considered.

Phosphorus cycling in wheat pasture rotations .I. The source of phosphorus taken up by wheat

Wheat plants (Triticum aestivum cv. Warigal) were grown in the field in a solonized brown soil (Calcixerollic xerochrept) to which 33P-labelled medic residues (Medicago truncatula cv. Paraggio) and 32P-labelled fertilizer had been added. Amounts of 31P, 32P and 33P in the wheat plants were determined at 7, 18, 32, 46, 61, 81 and 95 days after sowing. The 32P uptake by the wheat plants increased throughout the experiment and reached 11 -6% of the isotope applied by 95 days. Of the 33P applied in the medic residues, 5 -4% was recovered in the wheat plants. Most of the P taken up by the wheat plants was from soil P (i.e, from sources not added that season).

Phosphorus Uptake from Soil by Lolium perenne During and After Severe Drought

(1) Mature Lolium perenne plants grown in soil were subjected to gradually increasing drought, and their uptake of phosphorus was determined during and after the drought. (2) Relatively mild drought (soil matric potentials -06 to -08 MPa) stopped phosphorus uptake, probably because phosphorus in the drying soil became unavailable. (3) After drought, the rates of uptake of phosphorus and of applied 32p from rewetted soil were reduced. (4) Some recovery in rate of phosphorus uptake occurred two to three weeks after rewetting. (5) The reduction in 32p uptake following drought was approximately the same whether the plants were mycorrhizal or not. (6) The control of the reduced uptake was located in the root.

Phosphorus Turnover in Soil and Its Uptake by Established Lolium perenne Plants

(1) A technique is described for measuring the time-course of uptake of 32p from soil by Lolium perenne plants. (2) Carrier-free 32p was applied to the soil and the 32p content of leaves was determined non-destructively every 1 or 2 days. When 32p uptake had almost ceased the plants were harvested and their total 32p content was determined. (3) Well-established plants took up 10-40% per day of the phosphorus in the soil labile pool. The transfer in the soil from labile to non-labile forms per day always exceeded this. (4) Since the amount of phosphorus in the labile pool cannot have been changing rapidly, phosphorus transfer from non-labile to labile and from labile to non-labile forms must have been going on simultaneously and rapidly. The half-time for phosphorus residence in the labile pool was about 1-2 days. (5) The method has potential for the further study of phosphorus turnover and uptake in pots and in the field.

Root histology, and nutrient uptake and translocation in tissue culture plantlets and seedlings ofThuja occidentalis L.

Histological studies of the vascular connection in the root-shoot junction of tissue culture-derived plantlets and seedlings ofThuja occidentalis L. (Eastern white cedar) showed that in both plant types the xylem was well developed, smooth and not disrupted. Uptake and translocation of32P and86Rb were also similar for plantlets and seedlings. However, approximately 50% more86Rb could be desorbed from the root Donnan free space of plantlets than from seedlings. Uptake and translocation to the shoot was higher for86Rb than for32P, but no differences were found between the plant types. Tracer translocation rates to the shoot seem to be positively correlated with shoot fresh weight.

Impairments in hepatocyte phosphoinositide metabolism in endotoxemia

The status of phospholipid metabolism and inositol lipids-mediated transmembrane signaling in rat hepatocytes was analyzed during chronic, nonlethal endotoxemia. Rats were infused intravenously (IV) with Escherichia coli endotoxin (ET) via subcutaneously implanted osmotic pumps at a rate of 0.1 mg 100 g bw/day . The experiments were performed after 30 hours of ET or sterile saline (NaCl) infusion, in hepatocytes prelabelled “in vitro” with 32P (15 μCi/mL) and further stimulated with vasopressin (VP, 0.23 μmol/L). Similar experiments were done with food-restricted animals, whose food intake was matched with the voluntary intake of ET-infused rats. Uptake of 32P label into phosphatidic acid (PA), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP 2) occurs rapidly in cells from pair-fed, saline and ET-infused animals, and reaches a plateau between 60 and 80 minutes of incubation. Labeling of phosphatidylinositol (PI), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) proceeds linearly after a ten-minute lag period for PI and 20 minutes for the two other lipids. The nutritional state greatly affects the distribution of 32P uptake into lipids, resulting in very low labeling of PA and PI and a high labeling of poly-PI as compared with control (taken from untreated rats) cells. In ET- v saline-infused rats, the labeling of PI and PE was depressed concomitantly with a proportional increase in the labeling of PIP and PC. The ability of VP to induce polyphosphoinositide (poly-PI) degradation in hepatocytes from saline-infused animals was similar to that observed in control cells. The rapid loss in PIP 2 and PIP labeling (50% and 35%, respectively, within 30 seconds) was paralleled by an increase in 32P uptake in PA and followed by a later increase in PI labeling (150% at five minutes), and a sustained labeling of poly-PI towards prestimulation levels. In ET-infused rats, the early poly-PI response to VP stimulation was inhibited by 40% with no subsequent recovery in the PIP 2 labeling up to the last sampling time (five minutes). Also, the stimulation of PI turnover was 50% lower than that observed in saline-infused animals. The well-known stimulating effect of VP on 32P uptake into PI and PA when present from the start of incubation of the cells with the precursor, was abolished in ET-infused rats, while the labeling of PIP 2 was inhibited by 50%. In cells of saline-infused animals, 32P uptake into PA and PI was greatly increased, as in hepatocytes from control and pair-fed animals, with no effect at the level of poly-PI labeling. The results support the concept that ET infusion significantly perturbs changes in inositol lipid metabolism elicited by VP, affecting PIP 2 degradation and resynthesis at the plasma membrane level and PI turnover and/or synthesis in the endoplasmic reticulum.

Summer Drought Response and Rooting Depth of Three Cool-season Turfgrasses

Abstract This study was conducted to determine root distribution, soil moisture depletion, and 32P uptake, as an indicator of water absorption, by Kentucky bluegrass (Poa pratensis L. ‘Fylking’), perennial ryegrass (Lolium perenne L. ‘Manhattan’), and tall fescue (Festuca arundinacea Schreb. ‘Kentucky 31’). 32P was injected at 6, 18, 30, 42, and 54 cm from the soil surface under each turfgrass plot on 18 July 1978. Leaf blade radioactivity revealed differences in uptake among species, but was inconsistent with rooting patterns. Root mass measurements below 36 cm in late August showed tall fescue > perennial ryegrass > Kentucky bluegrass. Root mass above 12 cm showed Kentucky bluegrass > tall fescue = perennial ryegrass. Soil water content (SWC) at three depths in August reflected root distribution for the three species. SWC was lowest under Kentucky bluegrass and highest under tall fescue at 6 cm. At 54 and 78 cm, SWC was highest under Kentucky bluegrass and lowest under tall fescue. SWC was better than 32P injection for detecting species differences in water uptake.

Insulin reverses enhanced incorporation of 32P into polyphosphoinositides in peripheral nerve of the streptozotocin diabetic rat.

The ability of insulin treatment to reverse altered phosphoinositide metabolism in sciatic nerve from streptozotocin diabetic rats was studied. Diabetes was induced in rats by means of a single injection of streptozotocin. Enhanced incorporation of 32P into phosphatidylinositol-4,5-bisphosphate (PIP2) was detectable as early as 8 days following intravenous injection of streptozotocin and was maximal after 4 weeks. Hormone treatment was initiated at this time by daily injections of protamine zinc insulin followed by the implantation of long-acting insulin osmotic minipumps, and 4 weeks later sciatic nerves were removed and incubated in the presence of [32P]orthophosphate. The increased labeling of PIP2 was completely reversed by hormone administration. In contrast, insulin (0.1 and 1.0 mU/ml) added to the incubation medium failed to reverse the altered pattern of 32P incorporation into PIP2. The uptake of 32P into PIP2 was greater than 80% higher into the proximal than into the distal portion of normal sciatic nerve when these were incubated separately. This metabolic difference was abolished in diabetic rats, although the incorporation into both segments was still significantly higher than in controls. These results strengthen the association of altered nerve PIP2 metabolism with the diabetic state and are consistent with the concept that experimental diabetic neuropathy is a distal axonopathy.

Effect of aluminum on 32P uptake and translocation by red spruce seedlings

32P uptake and translocation was simultaneously studied in 11-week-old red spruce (Picearubens Sarg.) seedlings that had been pretreated for 24 h in hydroponic culture with or without 10 mg Al L−1. Aluminum in solution enhanced the accumulation of 32P in roots by more than two orders of magnitude over uptake in control seedlings, while the translocation of 32P to apical buds and mature primary needles was reduced to 20.0 and 9.1% of control levels, respectively. Kinetic analysis of 32P uptake indicated that P absorption is mediated by an uptake system exhibiting Michaelis–Menten behavior from solutions ranging from 0.01 to 5.00 mM KH2PO4; uptake at 10.0 mM KH2PO4 was inconsistent with this model. Changes in the patterns of 32P uptake and translocation in seedlings treated with Al suggest that Al in solution altered accumulation processes.

The phosphoproteins of the sickle erythrocyte membrane

The uptake of 32P from exogenous 32 P i into membrane proteins of sickle erythrocytes has been analyzed. The phosphorylation of spectrin is normal in sickle cells. There is, however, a substantial increase in 32P in the sialoproteins of the membrane, which can be demonstrated after fractionation or selective proteolysis. Normal and sickle erythrocytes were separated on Stractan gradients and average cell age was determined using the remaining pyruvate kinase activity as a marker. The altered phosphorylation of sickle cells was not seen in young normal cells, suggesting that it was not related to cell age. The altered phosphorylation was also not correlated with the level of reticulocytes in these fractions. This result is further evidence for abnormalities in the sialoproteins of sickle erythrocytes and is the first demonstration of altered sialoprotein phosphorylation in the red cell.

Synthesis of Desoxyribonucleic Acid in Normal and Irradiated Cells and Its Relation to Chromosome Breakage

Summary(1) The normal mitotic cycle in the meristem of main roots of Vicia faba seedlings is estimated to take 30 h, of which 4 are spent in division, 12 between the end of division and the beginning of 32P uptake into new DNA, 6 in DNA synthesis as judged by 32P uptake, and 8 between the end of synthesis and the prophase of the next division.(2) A dose of 13 × 103 erg/g (140r) of X-rays does not immediately stop DNA synthesis in cells which are in or near the period of synthesis at the time of irradiation, but causes these cells to be delayed in entering division for a period of about 4 hours.(3) The same dose of X-rays causes cells which are at other stages of the mitotic cycle at the time of irradiation to be delayed in entering synthesis for a period of 10 h or more.(4) Neutron doses of 1·1, 2·4 and 4·9 × 103 erg/g and 13 × 103 erg/g of X-rays have, within the standard deviations, the same effect on the number of cells synthesising DNA during 12 h following irradiation.(5) The estimated delay in entering division in cells irradiated with three different doses of neutrons indicates that this delay is dependent on dose, and that neutrons are not markedly more efficient than X-rays in causing it.(6) It is concluded that the immediate delay in entering division which results from irradiation cannot be attributed to delay in DNA synthesis, and that delay in entering division and chromosome breakage respond differently to irradiation and are therefore initially independent effects.(7) The question is discussed of the possible relationship between the stages of maximum sensitivity to chromosome breakage by radiations and by chemicals and the stage at which DNA is synthesized.

The relative contribution of plant residues and fertilizer to the phosphorus nutrition of wheat in a pasture cereal system

Wheat plants (Triticum aestivum cv. Warigal) here grown in a solonised brown soil (Calcixerollic xerochrept) which had been previously cropped to medic (Medicago trunculata cv. Paraggio). The 33P-labelled medic residues and 32P-labelled monocalcium phosphate were added to the soil in factorial combination. Amounts of 31P, 32P and 33P in the wheat plants and in the soil microbial biomass were determined. Addition of residues depressed wheat dry weight, 31P and 32P uptake, while simultaneously increasing amounts of 31P and 32P incorporated into the microbial biomass. Addition of fertiliser had no effect on the proportion of plant P taken up from the residues, but significantly increased the proportion of microbial P derived from this source. The 31P held in the microbial biomass was significantly increased by both residue and fertiliser P addition, with the former having the larger effect. Of the total P applied to the soil, medic residues contributed approximately one-quarter of that supplied by the fertiliser. Of the total P in the wheat plant, medic residues supplied approximately one-fifth of that supplied by the fertiliser.

The effect of foliar application of fulvic acid on water use, nutrient uptake and yield in wheat

The effect of foliar application of fulvic acid (FA) on water use, nutrient uptake and yield in wheat was studied in pot experiments and in field trials. FA reduced the stomatal conductance of well-watered plants in pots from ~0.80 to ~0.25 cm s-1. The stomatal conductance of control plants fell continuously from ~0.85 m s-1 to almost zero over a 9-day drying cycle. Plants sprayed with FA at the beginning of the cycle maintained a stomatal conductance of ~0.30 cm s-1 for the whole period. Spraying with FA resulted in a higher level of chlorophyll in the leaves and a greater uptake of 32P by the roots. When droughted at ear-development stage, grain yield was depressed by 30%. Spraying with FA increased the yield of droughted plants to 97% of the irrigated controls. Field trials in North China demonstrated that when FA was used to decrease the water stress or the stress imposed by hot, dry winds during ear development, grain yield increased by 7.3-18.0%.