Antitranspirant Activity of Inhibitors of Cyclic Photophosphorylation

The antitranspirant activity of three inhibitors of cyclic photophosphorylation(2,4-dinitro-phenol, 2-chloromercuri-4,6-dinitrophenol, andsalicylaldoxime) on 6-week-old plants of Datura arborea wasexamined. The test compounds reduced transpiration and the effectpersisted for 12 d. The dry matter production by the plantswas not affected. The reduction in water loss was caused bystomatal closure. Inhibitors of cyclic photophosphorylation,by virtue of their prolonged action associated with a smalleffect on dry matter accumulation, may be useful as antitranspirants.     

Effects of Chemical Antitranspirants on Transpiration and Growth of Grass

The effects of foliar sprays of the metabolic inhibitors dodecenylsuccinicacid (DSA) and phenylmercuric acetate (PMA), as antitranspirants,were tested on grass grown outdoors (in lysimeters), but moreaccurate tests were made with PMA in growth rooms, using smallweighable transpirometers. Concentrations of PMA which wereweaker than 10^-3.8 M resulted in only slight reductions in transpiration,whereas concentrations stronger than 10^-3.2 M were phytotoxic,though water losses were reduced by about 30 per cent. PMA at10^-3.5 M gave the greatest decrease in transpiration (about20 per cent) without reducing growth, but its effectivenessdepended on the amount applied per unit area of vegetation.The effects of PMA also differed with plant species and withenvironment, being greatest under conditions of low soil moisturestress and temperature. The antitranspirant reduced stomatalapertures and increased leaf temperatures.     

Effects of antitranspirants on distribution and utilization of photosynthate in Pinus resinosa seedlings

When 3-year-old Pinus resinosa Ait. seedlings were exposed to C¹⁴O₂ 24 hours after application of Aqua Gro, CS 6432, or Wilt Pruf antitranspirants, more activity was recovered from treated seedlings than from control seedlings 1 day after exposure to C¹⁴O₂. However, less activity was recovered when seedlings were exposed to C¹⁴O₂ 11 days after treatment with any antitranspirant except Clear Spray. Clear Spray, Folicote, and Keykote reduced accumulation of photosynthate, but their effects diminished with time. They also reduced the rate of loss of currently produced photosynthate, with the utilization effect most pronounced in Folicote-treated seedlings. All antitranspirants tested, except Aqua Gro and CS 6432, initially reduced the rate of conversion of labelled photosynthates into ethanol-insoluble components when treated seedlings were exposed to C¹⁴O₂ 24 hours after antitranspirant application. More labelled ethanol-insoluble components were recovered from antitranspirant-treated seedlings than from controls 14 days after exposure of seedlings to C¹⁴O₂. The type of spray, time between antitranspirant application and exposure to C¹⁴O₂, as well as the time between exposure and seedling harvest, had significant effects on C¹⁴ assimilation and redistribution of soluble and insoluble assimilates in various plant parts. Many of the observed effects may not have been directly due to the antitranspirants alone but may have been secondary effects caused by antitranspirant-induced changes in photosynthesis and plant water balance. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison. The cooperation of Professor D. M. Adams and the Wisconsin Department of Natural Resources is acknowledged. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison. The cooperation of Professor D. M. Adams and the Wisconsin Department of Natural Resources is acknowledged.     

Studies with antitranspirants on tea (Camellia sinensis L.)

The antitranspirant effect of a number of substances on tea was studied and the effects of the most effective substance investigated in detail. The film type of antitranspirants reduced transpiration only at a considerably higher concentration than the stomatal type of antitranspirants. Of the stomatal type of antitranspirants phenyl mercuric acetate (PMA) was the most effective substance. Under actively transpiring conditions a 250 ppm solution of PMA reduced transpiration by about 30 per cent. The effect of PMA was localised and there was no translocation to untreated parts of the leaf blade. A spray of PMA reduced transpiration with gradually diminishing intensity for about 20 days, reduced vegetative growth of young plants grown both under non-water stress and water stressed conditions and reduced the yield of crop of mature plants during a drought. re]19760806     

Farnesol-like antitranspirant activity and stomatal behaviour in maize and Sorghum lines of differing drought tolerance

Abstract Potted seedlings of four lines of maize and Sorghum of differing drought tolerance were subjected to a single soil drying cycle and were only rewatered when the plants showed the first signs of wilting. Other plants remained well-watered throughout the experimental period. As plant water potentials decreased in the unwatered plants of three of the lines investigated (Sorghum Piper and M35-1, V-4146 and maize Farz 27), endogenous levels of farnesol-like antitranspirants increased. Closure of stomata correlated well with the increase in endogenous antitranspirant. In the fourth line (Sorghum M35-1, V-4184), stomata did not close as the level of plant water stress increased, although leaf diffusion resistance of even the well-watered plants of this line was quite high. In this line, there was no consistent relationship between plant water stress and antitranspirant level or between stomatal behaviour and antitranspirant level. The involvement of farnesol-like antitranspirants in the control of stomatal behaviour in water-stressed plants is discussed.     

Effects of Abscisic Acid and its Esters on Stomatal Aperture and the Transpiration Ratio

A single surface application of abscisic acid or its methyl and phenyl esters suppressed stomatal opening on leaves of Xanthium strumarium. The effect was restricted to the treated parts of the leaf blades, there being no detectable translocation to untreated parts. There were no increases in CO₂ compensation to which stomatal closure could be attributed. Abscisic acid and its esters acted successfully as antitranspirants when applied once to leaf surfaces of young barley plants. Over a 9-day period there was a reduction of about 50% in the amount of water transpired without any detectable reduction in the rate of dry weight increase. The treatments reduced transpiration relatively more than dry matter accumulation, and hence there was an increase in the water use efficiency. The effect of the treatments became progressively less over 9 days, but even at the end of the experiment (day 9) both the esters reduced transpiration by 20–25%. The esters were slightly more effective than abscisic acid itself. On the basis of the data presented here, field trials of the antitranspirant properties of these compounds are recommended.     

Chitosan antitranspirant activity is due to abscisic acid-dependent stomatal closure

Chitosan (CHT) is a natural compound able to activate the plant own defence machinery against pathogen attacks and to reduce both transpiration and stomatal opening when applied as foliar spray. The data here reported show that CHT-induced antitranspirant activity in bean plants is mediated by ABA, whose level raised over threefold in treated leaves, 24 h after foliar spraying. This is thought to induce partial stomatal closure via a H₂O₂-mediated process, as confirmed by scanning electron microscopy (SEM) and histo-cytochemistry, and, in turn, a decrease of stomatal conductance to water vapor (G_w) and transpiration rate (E), assessed by gas exchange measurements. The relatively high internal CO₂ concentration (C_i) values, suggest the occurrence of a slight decrease in carboxylation efficiency after CHT treatment, which however did not prevail over stomatal limitations. The intrinsic water use efficiency (WUE_i) of CHT treated plants was not statistically different from controls and the maximal photochemical efficiency (F_v/F_m) of PSII was not affected. Moreover, CHT determined a stimulation of the xanthophyll cycle towards de-epoxidation state. On the whole, these results, besides confirming the effectiveness of CHT in reducing plant transpiration, prove that the mechanism underlying this activity differs from that showed by the commercial antitranspirant Vapor Gard^® (VP). In fact, the efficacy of the latter is based on the formation of a thin antitranspirant film over the leaf and not on the reduction of stomatal opening. Finally, suggestions for possible use of the two antitranspirants in different environmental conditions are discussed.     

Bark stripping in cork oak (Quercus suber L.): effect of an antitranspirant application on gas exchange and water relations of the stripped surface

Quercus suber L. is the primary source of industrial cork, which can be legally collected every 9 years. The main objective of this work was to test the efficiency of an application of an antitranspirant, at three different concentrations, after the bark stripping. For this purpose, several measurements of the gas exchange, water potential, total chlorophylls and the carotenoids contents were determined in cork oak trees, at two times in a day, morning and afternoon. The antitranspirant film was applied immediately after stripping. Transpiration rate showed a significant increase in the afternoon. The parameters, water potential, photosynthetic rates, stomatal conductance and the intrinsic water use efficiency, showed a significant decrease from morning to afternoon. The difference between pigments concentration was not significant throughout the day. Water potential and transpiration rate were high in the treatments with lower antitranspirant concentration. However, the treatment with a higher paraffin concentration showed larger photosynthesis rate. This result suggests that the loss of water observed for the stripping surface can be minimized by a larger concentration of the antitranspirant.     

Effects of abscisic acid and its acetylenic alcohol on dormancy, root development and transpiration in three conifer species

Abscisic acid (ABA) and a synthetic analog, the 2- cis acetylenic alcohol, were compared to evaluate their effectiveness in conditioning seedlings of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco], Engelmann spruce ( Picea engelmannii Parry) and lodgepole pine ( Pinus contorta Dougl.). Following preconditioning with ABA and the analog, seedlings were water stressed with the osmoticum polyethylene glycol (PEG) 3350. The effects of the growth regulators on transpiration, net photosynthesis, their ratio, called water use efficiency, and cell water relations parameters were then compared in stressed and unstressed plants. The antitranspirant action of these compounds varied depending on the species, the growth regulator, and the level of stress. ABA promoted transpiration in unstressed seedlings for all 3 species seven days after application. The analog was superior to ABA as an antitranspirant in osmotically-stressed lodgepole pine and Engelmann spruce, but neither compound was effective in Douglas-fir. For Douglas-fir and Engelmann spruce, net photosynthesis remained consistently higher in ABA-treated plants during the two levels of osmotic stress, relative to control and analog treatments. Neither compound had any effect on root development or cell water relations. ABA, and to a lesser extent its analog, hastened terminal bud formation in seedlings exposed to short days and low temperatures.     

Relationship between leaf temperature, compatible solutes and antitranspirant treatment in some desert plants

Three desert perennials from the Wahiba Sands, Oman were studied for their ability to withstrand high air temperatures combined with low water availability. Plants were also sprayed with antitranspirant to reduced water loss. This limited the potential for evaporative leaf cooling and resulted in high leaf temperatures in Prosopis cineraria (Druce) and Zygophyllum qatarense (Hadidi). Diurnal measurements were made of leaf and air temperature and of of photosynthesis and transpiration. Antitranspirants did not significantly reduce transpiration in Heliotropium kotschyi (Guerke), which contained high concentrations of the quaternary compound betaine. Transpiration continued through the hottest periods of the day and appeared to be essential for leaf cooling. All species appeared to have a threshold leaf temperature above which photosynthesis was severely impaired. Samples were taken for analysis of amino acids, quaternary ammonium compounds (QACs) and low molecular weight carbohydrates in conjunction photosynthesis and transpiration in order to examine any possible protective functions. In Prosopis cineraria the background concentration of the cyclitol, pinitol was high but there was no increase in response to the antitranspirant induced increase in leaf temperatures. Proline concentration increased in leaves of Zygophyllum qatarense throughout the day but this did not appear to be related to leaf temperature.     

Effect of antitranspirant treatment on the water balance of pine seedlings,under different climatic and soil moisture conditions

Summary Antitranspirant treatment with Tag — a polyethylene based emulsion-reduced transpiration and increased height of potted pine seedlings under simulated hot and dry conditions when soil was moist. Under cool, humid conditions reduction of transpiration was very much less and growth was slightly reduced. Application of antitranspirants to pine seedling transplants, under hot dry field conditions, failed to improve, their water balance or to reduce mortality. Physiological tests made during the field trial and experiments with potted seedlings showed that when the soil is dry xeromorphic plants efficiently reduce their water loss and under such conditions anti-transpirants are of no benefit. It is calculated that antitranspirants would only be advantageous under moist soil and high evaporative demand conditions.     

DESICCATION OR FREEZING? MECHANISMS OF WINTER INJURY TO RED SPRUCE FOLIAGE

Selected branches of red spruce {Picea rubens Sarg.) saplings growing at 900 m in elevation on Camels Hump Mountain, Vermont, were treated with an acrylic polymer antitranspirant (Adkar Cloud Cover) in October 1989. Winter injury was subsequently apparent on first-year foliage on 1 February 1990. Addition of antitranspirant significantly increased chloroform extractable wax (plus antitranspirant) weight and cuticle (plus antitranspirant) thickness. The treatment reduced cuticular transpiration under laboratory conditions, but did not lessen the severity of visually apparent winter injury. Xylem water potential of damaged and undamaged branches did not differ. Fresh to dry weight ratios revealed a tendency for damaged needles to desiccate rapidly following winter injury. Foliar pigment concentrations were negatively correlated with severity of winter damage. These results suggest that winter desiccation plays a minor role in inducing winter injury to red spruce foliage.     

Antitranspirant Activity in Xylem Sap of Maize Plants

Xylem sap from unwatered maize plants was collected and testedfor antitranspirant activity. Two assays were used. These werea transpiration assay with detached wheat leaves and a stomatalbio-assay involving the direct microscopic observation of epidermisof Commelina communis. The reduction in transpiration of detached wheat leaves promotedby xylem sap could be duplicated almost exactly by the applicationof solutions of ABA of equivalent concentration to that foundin the xylem sap. Removal of virtually all the ABA from thexylem sap, using an immunoaffinity column, removed virtuallyall the antitranspirant activity in both assays. These results are discussed in the context of other resultswhich suggest the presence of as-yet unidentified inhibitorsin the xylem sap of unwatered plants. We suggest that with maize plants at least, stomatal responsesto soil drying can be entirely explained by enhanced concentrationof ABA in the xylem stream. Key words: Antitranspirant activity, ABA, ABA bio-assay, xylem sap     

Responses of stomata of barley and maize to phenylmercuric acetate

A reduction of stomatal aperture in light was found in leaves of maize after they had been treated with 10“3-5 m phenylmercuric acetate (PMA). Complete closure of the stomata in darkness was prevented, whilst there was total closure in the controls. Higher PMA concentrations had bigger effects. The relative water content (RWC) of barley tissues was slightly reduced 12 hours after treatment with PMA. The transpiration rate observed on PMA-treated barley plants was lower in light and higher in darkness than in untreated plants. Water saturation deficit (WSD) was higher by about 5%, and water holding capacity (WHC) lower (25%) than in untreated plants. The results suggest that the concentration of PMA normally applied as an antitranspirant is unfavourable for healthy growth of maize and barley.     

Transpiration in wet meadows and some other types of Grassland

Transpiration rate in four types of alluvial meadows has been studied. Water wapour output of different grassland communities seems to be proportional to their biomass, bearing no relation to the species composition even though transpiration of individual species differed considerably. The relation between the above-ground biomass and the daily transpiration has been ascertained for wet, mesophytic and dry grassland and seems to be constant under similar sets of environmental conditions. The coefficient for estimating the daily transpiration in meadows from their biomass is presented.     

Antitrssanspirant action of abscisic acid and ten synthetic analogs in black spruce

A rapid screening procedure was developed to compare the antitranspirant action of abscisic acid (ABA) and ten synthetic analogs under well-watered and droughted conditions. Compounds were applied to black spruce [ Picea mariana (Mill.) B.S.P.] seedlings at 10 μ M using an aerated root drench. The plants were grown aeroponically under a continuous mist in a misting chamber and a drought stress was then applied, 7 days after treatment with the growth regulators, by switching off the misting unit for 2 h. The activity of 2- cis and 2- trans isomers of 4- transepoxy –β-ionylideneacetic acid, their corresponding methyl esters, and 4 acetylenic analogs were compared with ABA and control, untreated seedlings. Stomatal conductance and transpiration rates declined in treated seedlings after 3 h, but returned to pre-treatment levels 2–7 days after treatment. However, transpiration declined significantly as a result of ABA- and analog-treated seedlings when they were drought stressed 7 days after treatment. Since transpiration declined more than net photosynthesis, water use efficiency increased by up to 75% as a result of ABA analog treatment. The 2- cis -isomers of epoxy-β-ionylideneacetic acids and acetylenic alcohol analogs reduced transpiration and improved water use efficiency more than ABA and 3 out of the 4 2- trans isomers.     

The Effects of Transverse Cuts Through the Stems of Transpiring Woody Plants on Water Transport and Stress in the Leaves

Both single and double-overlapping transverse cuts were madein the stems of transpiring plants (Acer pseudoplatanus andGossypium hirsutum) and their effects on transpiration and waterstress in the leaves studied. Water stress was measured as depressionof water potential and ß-gauge reading. Results weresimilar with both species. Single cuts severing as much as 90 per cent of the cross-sectionalarea of the stem had no detectable effect on the rate of transpirationor on stress in the leaves above. Double overlapping cross cutscaused irreversible increased stress and cessation of sap flowonly if their vertical separation was less than a critical distance,specific for each species and related to the respective vessellengths. Cuts separated by more than this distance had no detectableeffect on stress and transpiration rate was unchanged. Alsono effect was detected if a length of the stem between suchcuts was cooled to near-freezing temperature, or killed by steamtreatment. Patterns of heat pulse velocities showed how thesap was channelled around the cuts through remaining intactxylem.     

Study of the Efficiency of Hydrasyl as an Antitranspirant with an Isotopic Method

The antitranspirant efficiency of Hydrasyl varies when it is sprayed over the blade surface of different plant species. The efficiency index of Hydrasyl was obtained by comparing the enrichment of tritium in water of a treated blade with that in a non-treated blade. The variability of the results depends on the specific regulation of water loss within the plant (physiological parameter) or on the “wettability” qualities of the cuticle (morphological parameter). The study brings to light the limits in the use of an antitranspirant.     

矮嵩草草甸植物蒸腾强度的初步研究

 此项研究工作于1986年5—9月植物生长季节内,在海北高寒草甸生态系统定位站进行。用钴纸法测定了矮嵩草等10种植物的蒸腾强度、垂穗披碱草等3种植物的蒸腾日进程和不同植被覆盖地段的蒸腾—蒸发量,在测定时记录了气温、湿度等有关气象资料,以便分析。研究结果表明：1．矮嵩草等10种植物的蒸腾强度随植物种和所处的物候期而变化,植物生长早期蒸腾强度较低,进入生殖阶段,蒸腾强度明显提高。2．垂穗披碱草等3种植物蒸腾强度日进程呈明显的单峰型曲线,在中午或午后出现峰值,没有午休现象。这同气孔一直开着有关,是矮嵩草草甸植物蒸腾的特征之一。 3．不同植被覆盖地段的蒸腾—蒸发表明,有植被覆盖的地段的蒸腾—蒸发量较裸地的蒸发量为高。     

Water relations of understorey shrubs in a Banksia woodland,Swan Coastal Plain,Western Australia

Abstract Diurnal and seasonal water relations were measured in understorey species from a Banksia woodland. The shrubs exhibited various responses to summer drought. Stirlingia latifolia had high xylem pressure potential and transpiration in late summer. Adenanthos cygnorum maintained high xylem pressure potential year round with dawn values around ? 0.3 MPa and minimum values around ?1.3 MPa, but showed severe restriction of transpiration in late summer. Eremaea pauciflora and Jacksonia floribunda had high transpiration and xylem pressure potential levels in early summer, but exhibited water stress in late summer when transpiration rates were low and minimum xylem pressure potentials were as low as ? 5.5 MPa. Late summer xylem pressure potentials in 27 other shrub species were, in general, inversely related to root system depth with minimum values below ? 5.0 MPa in some species. The water relations of S. latifolia, E. pauciflora and J. floribunda indicated a phreatophytic habit: all possessed deep roots of sufficient size to reach groundwater that was located 6–7 m deep at the study site. Stirlingia latifolia functioned phreatophytically year round, while E. pauciflora and J. floribunda were phreatophytes until the falling water table carried ground-water beyond the reach of their roots in late summer. However, most understorey species depended on soil-stored water. Water use by the understorey was greatest in early summer.