Chin J Plant Ecol ›› 2010, Vol. 34 ›› Issue (12): 1454-1462.DOI: 10.3773/j.issn.1005-264x.2010.12.012

• Research Articles • Previous Articles     Next Articles

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

WEI Xing, WANG Zheng-Quan*(), ZHANG Guo-Zhen   

  1. School of Forestry, Northeast Forestry University, Harbin 150040, China
  • Received:2009-09-15 Accepted:2010-08-04 Online:2010-09-15 Published:2010-12-28
  • Contact: WANG Zheng-Quan


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 H2O2 content, 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