Studies in Stomatal Behaviour: V. THE ROLE OF CARBON DIOXIDE IN THE LIGHT RESPONSE OF STOMATA

It was found that stomata on illuminated leaves, both of Pelargoniumand wheat, opened much wider where the leaf surface was enclosedin a small volume of air, as in a normal porometer cup, thanelsewhere. This was shown for both species by the infiltrationmethod, and for Pelargonium by Lloyd's method and direct microscopicalobservation also. The effect was shown not to be due to pressure of the porometercup or glass plate on the leaf, or to temperature differences,nor directly to the lack of movement or high humidity of theenclosed air. A considerable body of data was collected which appeared tosupport the hypothesis that the wide opening was due to accumulationof some volatile substance produced by the leaf, but all theresults were also consistent with the view that it was causedby reduction in the carbon dioxide content of the enclosed airbelow the normal 0·03 per cent. owing to photosynthesis.Further crucial experiments with both the porometer and infiltrationmethods left virtually no doubt that the latter hypothesis wascorrect. This extreme sensitivity of stomata to carbon dioxide concentrationwithin the range 0·03 per cent. to zero is discussedin relation to their operation in nature, and a possible biologicaladvantage is suggested. The bearing of the effect upon porometer investigations is alsodiscussed and it is concluded that for all quantitative or semi-quantitativeexperimentation it is essential to use a cup detached betweenreadings, or at least swept with air such as surrounds the restof the leaf, and to have the upper leaf surface above the cuparea freely exposed or similarly swept. For qualitative investigationof the light response of stomata the traditional form of cupmay be used. The importance is stressed of allowing porometer readings toreach equilibrium under one set of conditions before changingto another, when investigating the ‘closing’ or‘opening’ effects of external factors. Several subsidiary effects, observed in the course of the investigation,are discussed; in particular an effect of humidity upon therate of response to other factors.     

The prevention of cell division by anti-clotting agents

Summary We have continued to interpret cell division in terms of the colloidal theory. This theory maintains that cell division is initiated by those substances which induce mitotic gelation and is prevented by those which inhibit this gelation, and that furthermore the mitotic gelation represents a type of clotting in many respects similar to the clotting of vertebrate blood. The bacterial polysaccharide of Shear, a substance which has a marked effect in causing regression of tumors, is a heparin or heparinlike substance. It prevents mitotic gelation and cell division in theChaetopterus egg. Dicoumarol has marked effects on protoplasmic viscosity, first causing enhanced gelation and then pronounced liquefaction. Its action on cell division is related to these effects. A synthetic vitamin K (2-methyl-1, 4 naphthoquinone) tends to liquefy and then markedly to clot the protoplasm of theChaetopterus egg. In very low concentrations it stops mitosis irreversibly.Aided by a grant from the U. S. Public Health Service.     

LIQUID NITROGEN IN THE TREATMENT OF SKIN DISEASES

Liquid nitrogen is a satisfactory freezing agent in the treatment of such skin diseases as warts, keratoses, superficial hemangiomas, leukoplakia, keloids, superficial scarring and dermatitis venenata. It is available and easily applied. Its use is described and the results of treatment in 154 cases of warts are presented.     

A cortical cytoskeleton in expanded epithelium cells of sponge gemmules

Electron micrography seems to have revealed the existence of a fibrous cytoskeleton in the cortex of the basal epithelium of sponge gemmules adhering to the substrate.     

Study of the growth and development of chlorella populations in the culture as a whole

Исследовалась цитоморфология двух видов Chlorella в условиях, при которых наблудается в боляшей или меняцей степени циссоциация процессов роста и размножения. В средах различного состава можно было наблуюдатявполне тиничный и воспроизводимый характер (trend) роста и развития кулятуры как целого. Chlorella в основном размножается так, как размножаются клеточные ядра, митохондрии и пластиды. Из них и из их плазмы строятся постепенно сначала безоболочечные и поцвижные проаутоспоры, которые, приобретая оболочку, преврацаются в непоцвижные аутоспоры. Экбалаты и экбластаты —это различные формы ранних фаз развитня проаутоспор. Недостаток магния и серы вызывает быстроепрекрацение способности к размножению и преобладания роста в величниу в сравнении со способностяю водорослей к делению. Чрезмерный рост в величину у Chlorella является не признаком физиологического благополучия, а признаком дегенерации. При зтом Chlorella подвергается вакуолизации и позднее погибает, обычно в результате осмотического растягивания.