Tag: Heath O. V. S.

Values of gamma give a good measure of the efficiency of the mesophyll for net carbon dioxide absorption, with the stomatal factor eliminated

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“伽玛值为测量叶肉对净二氧化碳吸收效率的重要指标，排除气孔因素的影响。”

Valores de gamma fornecem uma boa medida da eficiência do mesofilo para a absorção líquida de dióxido de carbono, com o fator estomático eliminado.


Los valores de gamma proporcionan una buena medida de la eficiencia del mesófilo en la absorción neta de dióxido de carbono, con el factor estomático eliminado.

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The influence of water strain on the minimum intercellular space carbon dioxide concentration Γ and stomatal movement in wheat leaves 

Heath O. V. S., Meidner H. (1961)

Heath O. V. S., Meidner Hans,

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J. exp. Bot. 12: 226-242 – https://doi.org/10.1093/jxb/12.2.226 –

https://academic.oup.com/jxb/article-abstract/12/2/226/621553?redirectedFrom=fulltext&login=false

Abstract

Eight detached wheat leaves were each subjected to varying degrees of controlled water strain, in a specially constructed leaf chamber (which is described in detail) connected to a closed system incorporating an infra-red gas analyser. The water strain was varied by applying successively to their leaf sheaths two concentrations of mannitol solution (0·2 M. and 0·4 M.) each preceded and followed by water. Conditions were maintained constant for light (900 f.c.), leaf temperature (25° C.) and humidity (50 per cent. RH) of the circulating air as it entered the leaf chamber. Steady-state values (gamma) of the carbon dioxide concentration in the closed system were recorded both for the water and mannitol treatments and the data analysed statistically. The two mannitol treatments were found to increase gamma from 80 p.p.m. with water to 94 and 116 p.p.m. respectively, all differences being highly significant. Concomitant measurements were made of stomata1 resistance with a porometer and of transpiration by means of wet and dry thermocouples; the stomata showed marked closure in response to mannitol treatment (complete closure with the higher concentration) and partial reopening with the leaf sheath in water once more, transpiration also falling and rising inversely with water strain.

It is concluded that part of the closing response of wheat stomata to water strain under natural conditions must be operated by increase in the intercellular-space carbon dioxide concentration, but a comparison with previous experimental results suggests that this can only be a small part unless sensitivity to carbon dioxide is greatly increased by water loss.

The initial response to mannitol treatment was a preliminary opening of the stomata and a fall of about 10 per cent. in carbon dioxide concentration. These results imply that under natural conditions the preliminary opening of wheat stomata with wilting may be partly passive and partly active with a carbon dioxide-operated mechanism.

A subsidiary experiment with water strain varied by removing and restoring the water supply to the leaf sheath gave increases and decreases in carbon dioxide similar to those in the main experiment; the results of the latter need not, therefore, be attributed to metabolism of the mannitol.

It is suggested that values of gamma give a good measure of the efficiency of the mesophyll for net carbon dioxide absorption, with the stomatal factor eliminated, under the given conditions and with carbon dioxide ‘limiting’ in the sense used by Maskell (1928).

The Use of the Resistance Porometer in Estimating Stomatal Aperture

Experimental Studies of the Relation between Carbon Assimilation and Stomatal Movement: II. The Use of the Resistance Porometer in Estimating Stomatal Aperture and Diffusive Resistance: Part I. A Critical Study of the Resistance Porometer withan appendix by HL Penman

Heath O. V. S., Penman H. L. (1941)

Annals of Botany 5(19): 455-500 – https://doi.org/10.1093/oxfordjournals.aob.a087402 –

https://academic.oup.com/aob/article-abstract/5/3/455/183313?redirectedFrom=fulltext

The resistance porometer and important errors due to the responses of the enclosed stomata to variations in CO2 supply

Experimental studies of the relation between carbon assimilation and stomatal movement. IL The use of the resistance porometer in estimating stomatal aperture and diffusive resistance

Spanner D. C., Heath O. V. S. (1951)

Ann. Bot. N.S. 15(3): 319-331 – https://doi.org/10.1093/oxfordjournals.aob.a083284 –

https://academic.oup.com/aob/article-abstract/15/3/319/165719?redirectedFrom=fulltext

Abstract

Two purely physical sources of error in the ‘resistance porometer’ as ordinarily used are considered to be of appreciable importance, viz. that due to the flow through the leaf being augmented with water vapour which is removed again by a drying agent before the air passes through the standard capillary, and that due to the leaf temperature differing from the capillary temperature. In a bad case the total error might amount to 10 or 15 per cent. of the ‘leaf resistance’.

Modifications to deal with these sources of error and with the more important errors due to the responses of the enclosed stomata to variations in CO2 supply are described.

Adequacy of the porometer in the investigation of stomatal aperture

Studies in stomatal action. Adequacy of the porometer in the investigation of stomatal aperture

Heath O. V. S., Williams W. T. (1948)

1 Research Institute of Plant Physiology, Imperial College, London, S.W.7.

2 Botany Department, Bedford College for Women, London, N.W.l.

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Nature (Lond.) 161: 178–179 – https://doi.org/10.1038/161178a0 –

https://www.nature.com/articles/161178a0#citeas

A recording resistance porometer is described which enables records of stomatal behaviour to be obtained concurrently from four different leaves

A recording porometer with detachable cups operating on four separate leaves

Heath O. V. S., Mansfield T. A., (1962)

Proc. Royal Soc. B – Biological Sci. – https://doi.org/10.1098/rspb.1962.0024 –

https://royalsocietypublishing.org/doi/10.1098/rspb.1962.0024

Abstract

A new form of recording resistance porometer is described which enables records of stomatal behaviour to be obtained concurrently from four different leaves; the porometer cups are automatically detached between readings, exposing the leaf surfaces to the ambient air in order to avoid artifacts due to changes in carbon dioxide concentration. The readings are recorded for the four leaves seriatim, the cup for each remaining attached for 3 min out of every ½ h. The results of several of the preliminary experiments carried out to test the new instrument are presented: 1. Continuous records for periods up to 6 days appear to have no serious effect on the functioning of the stomata under normal conditions. With Taraxacum officinale slightly greater stomatal opening was recorded on the fifth day than on the first; for wheat a slight falling off occurred on the third and fourth days, possibly due to ageing of the leaves. 2. The stomata of similar leaves on different plants which have been subjected throughout to the same sequence of conditions show remarkable uniformity of behaviour at any one time; a great increase in the precision of comparisons of experimental treatments should thus be achieved by applying them to such leaves and recording the results concurrently. 3. Experiments with plants of T. officinale, wheat and Xanthium pennsylvanicum subjected to increasing water strain have shown a marked closing response to the process of taking a reading (which involves forcing air through the leaf). This closing response is first seen some time before visible wilting occurs and for X. pennsylvanicum has been shown to be mainly if not entirely due to a greatly increased sensitivity to carbon dioxide. The biological implica­tions of this are discussed. The stomata (e. g. of T. officinale) may not re-open fully for 2 or 3 days after re-watering, when the plant is recovering from water strain, but the enhanced sensitivity to readings is only shown while water is actually in short supply, and not during the period of recovery.

Effects of anaerobic conditions upon stomatal movement

Studies in stomatal behaviour. VII. Effects of anaerobic conditions upon stomatal movement a test of Williams’ hypothesis of stomatal mechanism

Heath O. V. S., Orchard B., (1956)

J. of Exper. Bot. 7: 313–325 – https://doi.org/10.1093/jxb/7.3.313 –

https://academic.oup.com/jxb/article-abstract/7/3/313/546523?redirectedFrom=fulltext

Abstract

An experiment was carried out to investigate stomatal responses in wheat to four ‘closing treatments’, viz. high carbon dioxide concentration, darkness, dry air and nil, each given under both aerobic and anaerobic conditions. Thus the effect of lack of oxygen on the closing (or opening) tendency was estimated. Changes in (conductance)−−−−−−−−−−−√3(conductance)3 calculated from resistance porometer readings were used as data and reasons are given for thinking this is the best available measure for investigating stomatal dynamics in wheat. Williams’s hypothesis demands that lack of oxygen should cause stomatal opening or prevent closure; the present experiment shows that anaerobic conditions significantly increase the closing tendency when ‘closing treatments’ are first applied. There is also some suggestion that oxygen-lack itself tends to cause closure in the absence of any other ‘closing treatment’. Williams’s hypothesis in its original form is thus disproved (for wheat) but the present results would be consistent with an ‘active’ uptake of water by the guard cells contributing to stomatal opening. A nearly significant interaction between carbon dioxide and oxygen suggests that under anaerobic conditions a ‘closing substance’ may perhaps be formed, for example, by the union of some intermediate in glycolysis with carbon dioxide.

The interrelations of light intensity, CO2 concentration and rate of air flow in controlling the movement of stomata

Studies in stomatal behaviour. V. The role of carbon dioxide in the light response of stomata, Part II – Preliminary experiments on the interrelations of light intensity, carbon dioxide concentration and rate of air flow in controlling the movement of wheat stomata

Heath O. V. S., Milthorpe F. L., (1950)

Journal of Experimental Botany 1: 227-243 – https://doi.org/10.1093/jxb/1.2.227 –

https://academic.oup.com/jxb/article-abstract/1/2/227/573863?redirectedFrom=fulltext

Abstract

Experiments are described in which the responses of wheat stomata to carbon dioxide concentration (0·00, 0·01, 0·02, 0·03 per cent.), light intensity (275, 625, 975 f.c.), and rate of air flow (2, 5, 12·5 l./hr.) were studied.

Reduction of carbon dioxide concentration from 0·03 to 0·01 per cent. resulted in marked stomatal opening; further reduction to 0·00 per cent, was accompanied by a slight but not significant closure. These effects were found at all light intensities and rates of flow, except at 975 f.c. with 2 l./hr. air flow, where no effect of carbon dioxide concentration was detected. This last is attributed to excessive depletion of the carbon dioxide supply by assimilation. The apparent lower limit of 0·01 per cent, carbon dioxide causing maximal stomatal opening is discussed in relation to recent assimilation experiments.

Increase of light intensity caused considerable stomatal opening, this effect being as great with air of 0·00 and 0·01 per cent. as with higher concentrations of carbon dioxide. This suggests an effect of light on stomatal movement other than that exerted indirectly through photosynthesis by the mesophyl cells.

Increased rate of flow of dry air caused closure of the stomata; this was shown to be a drying effect and was absent when moist air was used.

The light response of stomata

Studies in stomatal behaviour. II. The rôle of starch in the light response of stomata. Part 2. The light response of stomata of Allium cepa L., together with some preliminary observations on the temperature response

Heath O. V. S. (1952)

New Phytologist 51: 30–47 –

https://nph.onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1952.tb06113.x

The relation between stomatal aperture and starch content in the stomata

Studies in stomatal behaviour. II. The role of starch in the light response of stomata. Part I. Review of literature and experiments on the relation between aperture and starch content in the stomata of Pelargonium zonale

Heath O. V. S. (1949)

New Phytol. 48: 186-211 –

https://www.jstor.org/stable/2429111