High light intensity protects photosynthetic apparatus of pea plants against exposure to lead

Four Solanum tuberosum L. cultivars (Nicola, Pito, Puikula, Timo) and somatic hybrids between freezing tolerant S. commersonii and freezing sensitive S. tuberosum were evaluated for their tolerance to freezing and low temperature photoinhibition. Cellular freezing tolerance was studied using ion leakage tests and the sensitivity of the photosynthetic apparatus to freezing and high light intensity stress by measuring changes in chlorophyll fluorescence (FV/FM) and oxygen evolution. Exposure to high light intensities after freezing stress increased frost injury significantly in all genotypes studied. Compared with S. tuberosum cultivars, the hybrids were more tolerant both of freezing and intense light stresses. In field experiments the mechanism of frost injury varied according to the severity of night frosts. During night frosts in 1999, the temperature inside the potato canopy was significantly higher than at ground level, and did not fall below the lethal temperature for potato cultivars (from -2.5 to -3.0°C). As a result, frost injury developed slowly, indicating that damage occurred to the photosynthetic apparatus. However, as the temperature at ground level and inside the canopy fell below -4°C, cellular freezing occurred and the canopy was rapidly destroyed. This suggests that in the field visual frost damage can follow from freezing or non-freezing temperatures accompanied with high light intensity. Therefore, in an attempt to improve low temperature tolerance in potato, it is important to increase tolerance to both freezing and chilling stresses.

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High light intensity aggravates latent manganese deficiency in maize

Journal of Experimental Botany ◽

10.1093/jxb/eraa366 ◽

2020 ◽

Vol 71 (19) ◽

pp. 6116-6127 ◽

Cited By ~ 1

Author(s):

Lizhi Long ◽

Pai R Pedas ◽

Rebekka K Kristensen ◽

Waltraud X Schulze ◽

Søren Husted ◽

...

Keyword(s):

Light Intensity ◽

Photosynthetic Apparatus ◽

High Light Intensity ◽

Photosynthetic Performance ◽

High Light ◽

Oxygen Evolving Complex ◽

Mn Deficiency ◽

Two Factors ◽

Genes Encoding ◽

Underlying Mechanisms

Abstract Manganese (Mn) plays an important role in the oxygen-evolving complex, where energy from light absorption is used for water splitting. Although changes in light intensity and Mn status can interfere with the functionality of the photosynthetic apparatus, the interaction between these two factors and the underlying mechanisms remain largely unknown. Here, maize seedlings were grown hydroponically and exposed to two different light intensities under Mn-sufficient or -deficient conditions. No visual Mn deficiency symptoms appeared even though the foliar Mn concentration in the Mn-deficient treatments was reduced to 2 µg g–1. However, the maximum quantum yield efficiency of PSII and the net photosynthetic rate declined significantly, indicating latent Mn deficiency. The reduction in photosynthetic performance by Mn depletion was further aggravated when plants were exposed to high light intensity. Integrated transcriptomic and proteomic analyses showed that a considerable number of genes encoding proteins in the photosynthetic apparatus were only suppressed by a combination of Mn deficiency and high light, thus indicating interactions between changes in Mn nutritional status and light intensity. We conclude that high light intensity aggravates latent Mn deficiency in maize by interfering with the abundance of PSII proteins.

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Differential Changes in the Photosynthetic Pigments and Polyamine Content during Photoadaptation and Photoinhibition in the Unicellular Green Alga Scenedesmus obliquus

Zeitschrift für Naturforschung C ◽

10.1515/znc-1998-9-1009 ◽

1998 ◽

Vol 53 (9-10) ◽

pp. 833-840 ◽

Cited By ~ 9

Author(s):

Kiriakos Kotzabasis ◽

Dieter Dörnem

Keyword(s):

Light Intensity ◽

Green Alga ◽

Scenedesmus Obliquus ◽

Photosynthetic Pigment ◽

Photosynthetic Apparatus ◽

High Light Intensity ◽

High Light ◽

Light Conditions ◽

Unicellular Green Alga ◽

Polyamine Level

In the unicellular green alga Scenedesmus obliquus the level of photoinhibition and the recovery of the cells after reversal to the initial light conditions in relation to the pre-photoadaptation of the culture to low, medium and high light intensity was determined. The changes in the photosynthetic pigment content and in the intracellular polyamine concentration allowed to distinguish between photoadaptation and photoinhibition. In particular, the level of chlorophylls, xanthophylls and carotenoids decreased inversely proportional to the light intensity applied during photoadaptation, whereas their concentrations remained constant during photoinhibition. The violaxanthin/zeaxanthin and the loroxanthin/lutein cycle work only under photoinhibitory conditions, but not under photoadaptive premises. Changes in the level of these carotenoids in relation to the changes in the photosynthetic apparatus during photoadaptation are discussed. In addition, it was found that the intracellular polyamine level increased only under stress conditions, i. e. during photoinhibition, and decreased during recovery of the cells after reversal to the initial light conditions. The increase of the putrescine level during photoinhibition is inversely proportional to the light intensity used for pre-adaptation. This rise of the polyamine level in the cells photoadapted to high light conditions is an additional indication for the finding that photoadaptation and photoinhibition are different phenomena which are clearly distinguishable from each other. Finally, the changes of the chlorophyll, violaxanthin, zeaxanthin, loroxanthin, lutein and polyamine levels under photoadaptation in high light intensity (50 W m -2) in relation to the range of photoadaptation in Scenedesmus obliquus are discussed.

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