Abstract In this study, wheat (Triticum aestivum L.) roots were treated with hypoxic water. The staining of cell preparations with DAPI revealed morphological changes of the cells such as nuclear condensation, deformation and fragmentation. Under TEM, cellular membrane shrinkage and breakage, chromatin condensation and apoptotic-like bodies were displayed. The number of mitochondria increased dramatically; their cristae were damaged; the interior became a cavitation and only some flocculent materials were distributed. Indirect immunofluorescence staining indicated that cytochrome C diffused from mitochondria to nucleoplasm and cytoplasm. TUNEL positive nuclei indicated double strand breaks of DNA. DAB staining was used for the identification of hydrogen peroxide and examination showed that the longer the treating time, the darker the staining of the meristematic zones of the roots which suggested the increased accumulation of these Reactive Oxygen Species (ROS). The elevation of hydrogen peroxide production was paralleled with the increase of SOD and POD activities. A negative correlation between the exposure time under hypoxia and the contents of soluble proteins was found. No obvious effect of hypoxia on MDA was established. The obtained results demonstrate that hypoxia causes programmed cell death in the root-tip meristematic cells of Triticum aestivum L. which is most probably attributed to the accumulation of large amounts of ROS.

Accumulation of LaCl3, a well-known Ca2+-channel blocker, can inhibit plant growth. However, the current understanding of its effects on gene expression is limited. In this paper, different concentrations of LaCl3 (0, 0.5, 1.0, 1.5, 2.0 mM) were used to treat germinated wheat ( Triticum aestivum L.) seeds for 24 h. The degree of root growth inhibition gradually increased with increasing LaCl3 concentration. qRT-PCR analysis revealed that the expression of several key genes related to the cell cycle process, such as pcna, mcm2, rdr and cyclin B, were significantly down-regulated. Further analysis of genomic DNA instability using Random Amplified Polymorphic DNA (RAPD) and methylation levels by Coupled Restriction Enzyme Digestion-Random Amplification (CRED-RA) analysis indicated a significant increase in genomic DNA polymorphisms and methylation levels. The results of this study verified that the reasons why LaCl3 treatment can inhibit the growth of wheat roots are as follows: interference in the normal progression of the cell cycle, induction of genomic DNA instability and increase in DNA methylation levels.