Morphological and activity variation of mitochondria in fine roots of Fraxinus mandshurica seedling under drought stress

doi:10.3773/j.issn.1005-264x.2010.12.012

Abstract

Abstract:

Aims In addition to producing energy, mitochondria in fine roots play a dual role in oxidative stress, being both reactive oxygen species (ROS) producers and integrators of the cell antioxidant defense systems. Structural integrity of mitochondria is the fundamental guarantee for producing ATP in fine roots. Therefore, our objective was to observe mitochondrial structural and functional changes in Fraxinus mandshurica fine roots of different colors under drought stress to better relate different-colored fine roots with different functions and to develop a theoretical basis for judging fine root death according to root color.
Methods We observed the number, distribution and structure of mitochondria in different-colored fine roots cortical parenchyma cells of F. mandshurica by electric microscopy. Mitochondrial respiratory control ratio (RCR) and phosphorus oxygen ratio were measured by oxygen electrode. The malondialdehyde (MDA) content, membrane permeability and H₂O₂ concentration were studied by UV spectrophotometer.
Important findings Compared with the control, there were no significant differences of mitochondrial shape, structure or distribution under drought stress in white and yellow roots’ cortical parenchyma cells. However, there were fewer mitochondria in brown fine roots under drought stress, and their membranes had disintegrated and disappeared to a different degree. The normal breathing coupling of mitochondrial membrane role in fine-root mitochondria was disturbed significantly under drought stress. The value of RCR and P/O were significantly lower than that of the control (p < 0.05). With deepened fine-root color, mitochondrial RCR and P/O value decreased gradually, white roots > yellow roots > brown roots. The H₂O₂content, mitochondrial membrane permeability and MDA content in different-colored fine roots mitochondria under drought stress were significantly higher than the control (p < 0.05). Values increased markedly with deepened color.

Key words: drought stress, fine root, Fraxinus mandshurica, mitochondria

WEI Xing, WANG Zheng-Quan, ZHANG Guo-Zhen. Morphological and activity variation of mitochondria in fine roots of Fraxinus mandshurica seedling under drought stress[J]. Chin J Plant Ecol, 2010, 34(12): 1454-1462.

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URL: https://www.plant-ecology.com/EN/10.3773/j.issn.1005-264x.2010.12.012

https://www.plant-ecology.com/EN/Y2010/V34/I12/1454

Figures/Tables 9

Fig. 1 Mitochondrial ultrastructures in cotical parenchyma of fine roots in Fraxinus mandshurica seedlings. A, White root of control. B, Yellow root of control. C, White root under drought stress. D, Yellow root under drought stress. E-O, Brown root under drought stress.

Fig. 2 Effects of drought stress on mitochondrial quantity of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Different small letters mean significant differences (p < 0.05) between drought treatments and control; different capital letters mean significant differences (p < 0.05) among different color fine roots.

Fig. 3 Effects of drought stress on mitochondrial respiratory state 3 of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 4 Effects of drought stress on mitochondrial respiratory state 4 of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 5 Effects of drought stress on mitochondrial respiratory control ratio (RCR) variations of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 6 Effects of drought stress on mitochondrial P/O value of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 7 Effects of drought stress on mitochondrial membrane light absorbability of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 8 Effects of drought stress on mitochondrial malondiadehyde (MDA) content of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

Fig. 9 Effects of drought stress on mitochondrial H2O2 content of fine roots with different color in Fraxinus mandshurica seedlings (mean ± SE). Notes see Fig. 2.

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