Effects of ozone water irrigation and spraying on physiological characteristics and gene expression of tomato seedlings.

Tomato seedlings were used as experimental materials and treated with 1.0, 2.0, 3.0, and 4.0 mg/L ozone water irrigation and 0.2, 0.4, 0.6, and 0.8 mg/L ozone water spray treatments. Indexes including the malondialdehyde (MDA) content, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), activities, soil and plant analysis development (SPAD) value, and nitrogen content of leaves were measured. Furthermore, the expression of antioxidant enzyme, chlorophyll synthesis and nitrogen absorption genes was analyzed after optimal ozone water treatment. The results showed that the activities of antioxidant enzymes in tomato leaves were significantly increased, and the MDA content in tomato leaves was significantly reduced by ozone water irrigation and spray treatment, which indicated that ozone water treatment can significantly improve the stress tolerance of tomato seedlings. Ozone water irrigation and spraying could also significantly increase the leaf SPAD value and nitrogen content of tomato seedlings, and the optimal concentrations of ozone water irrigation and spraying were 3.0 mg/L and 0.6 mg/L, respectively. The effect of ozone water irrigation on improving the physiological characteristics of tomato seedlings was better than that of spraying. After treatment with the optimal concentration of ozone water, the relative expression of antioxidant enzyme, chlorophyll synthesis, and nitrogen absorption genes was significantly increased, and the maximum expression level was reached at 12 h. In addition, ozone water irrigation could promote the expression of genes more than ozone water spraying, which was consistent with the improvements in the physiological characteristics of the tomato seedlings.

Distribution and re-transportation of sodium in three Malus species with different salt tolerance.

To further dissect the mechanism of salt tolerance in Malus, the comparison was made regarding the differences between the salt-tolerant and salt-sensitive species in sodium accumulation and extrusion capability in the roots and stem base as well as the sodium re-transportation from shoot to roots by using 22Na labeling-based feeding of leaves and roots-split experiments. The results demonstrated that the salt-tolerant Malus species could accumulate more 22Na in the main roots, lateral roots, stem base phloem and xylem, and extrude more sodium out than the salt-sensitive one. In addition, the salt-tolerant Malus species had the higher sodium re-transportation rate from shoot to roots. Altogether, it is concluded that the stronger sodium accumulation and extrusion in the roots and the stronger sodium re-transportation from shoot to roots in the salt-tolerant species play important roles in salt tolerance of Malus species.

[Auxin response factors and plant growth and development].

An important aspect of studies on auxin is auxin response factors (ARFs), which activate or repress the auxin response genes by binding to auxin response elements (AuxREs) on their promoters. In this review, we focused on molecular biological advances of plant ARF families, and discussed ARF structures, regulation of ARF gene expression, the roles of ARFs in regulating the development of plants and in signal transduction and the mechanisms involved in the target gene regulation by ARFs. The phylogenetic relationships of ARFs in plants are close and most of them have 4 domains. ARFs are expressed in various tissues. Their expressions are regulated at both transcriptional and post-transcriptional levels. They play important roles in the interactions between auxin and other hormones.