The Raw pH in Plants: A Multifaceted Parameter

Giorgio Masoero,Alberto Cugnetto,Abubaker Haroun Mohamed Adam

doi:10.14302/issn.2639-3166.jar-18-2397

Abstract

The measurement of the in vivo raw pH of vegetative organs is a unusual way obtaining plant knowledge. The authenticity of the pH parameter of the leaf and its independence from soil pH has already been highlighted. In the present work we observe how and to what extent water-temperature mechanisms as well as bio-fertilizers inocula can affect the raw pH and how great the biodiversity is in plants. A trial with Arabidopsis thaliana in a phytotrone has shown that, in the dark, the raw pH did not change from +18 to +35 °C (b = -0.0027 N.S.), while in the light, the regression coefficients were significant and negative, and the acidification in the leaves progressed from high (-0.0097) to normal (-0.0127) and then to low (-0.0370) water levels. We have confirmed that warming induces a decrease of raw petiole pH of -0.070 pH C°-1 in grapevine leaves. In accordance with water-temperature mechanisms, the raw pH in grapevines has been found to be significantly higher in well-watered plants (pH = 4.29) than in stressed ones (4.12), with a pH decay of -3.9%. On the other hand, an average reduction of 0.10 units of raw pH would signal an increase in water stress of about -0.59 Mpa. Among the phenomena that can influence the raw pH, we have outlined three biotic factors: i) acidification as a result of a symbiotic farming fertilization i.e through the use of mycorrhizal and microbial fertilizers, with an average decay of around -3%, as a probable signature of symbiosis; ii) an “acida plantarum natura” scenario over 49 species, ranging from pH 3.06 to 6.38 ; iii) a strong (R2= 0.9) inverse polynomial pseudo-relationship of the number of fungicide sprays on the raw pH in a set of 15 species. It is suggested that this simple new multifaceted parameter can deserve interest.

Highlights

The in vivo raw pH of vegetative organs is a unusual measurement in plant knowledge, that almost sounds like a paradox when compared to the resonant importance of soil pH1 or pH and Eh2 and of pH and Eh in hydroponics systems[3,4]
Raw pH fall-out in Sorghum sudanensis leaves has been recently recognised as a sign of mycorrhizal inoculation[11]
In the experiment with grapevine aimed to an assessment of the pH to the aerial temperature, it was observed a saddle trend from morning to evening (Figure 2)

Summary

Introduction

The in vivo raw pH of vegetative organs is a unusual measurement in plant knowledge, that almost sounds like a paradox when compared to the resonant importance of soil pH1 or pH and Eh2 and of pH and Eh in hydroponics systems[3,4]. In the framework of a study on mycorrhizal and microbial effects on maize[6] a systematic significant response emerged in the in vivo raw pH of maize stems, showing an acidification de-gradient from roots (pH -7% in mychorrized corn) to stem pH at ears height (-4%). After this first results, preliminary surveys in grapevine ascertained that the Flavescence dorée, a phytoplasma diffused in Latin EU-area[7] attack determined an elevation of the pH in unhealthy sub-branch and petioles[8]. A relevant result was the appearance of acidic nature in the raw tissues of corn and grapevine that were lower than the previous leaf pH values determinated in 92 species from the Cornelissen team[9,10]

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Conclusion