Responses of Aerobic Rice (Oryza sativa L.) to Iron Deficiency

Aerobic rice has the advantage of saving water. Most published work has focused on improving its yield, while few reported on its micronutrient status. In fact, Fe deficiency is a common nutritional problem in the production of aerobic rice. Short- term hydroponic culture experiments were conducted to study the response of aerobic rice to Fe deficiency and the effect of root exudates from Fe-deficient wheat on its Fe uptake ability. The results indicate that the amount of phytosiderophores （PS） released from aerobic rice did not increase under Fe deficient conditions. The Fe（III） reducing capacity of Fe-deficient aerobic rice did not increase and the solution pH did not decrease significantly. What＇s more, no obvious swelling was observed in the root tips. Aerobic rice did not show special responses to improve their Fe nutrition under Fe deficiency as both strategy I and II plants though they were very sensitive to Fe deficiency. This may be a reason which causes Fe deficiency problem in aerobic rice. However, root exudates from Fe-deficient wheat （PSw） could improve its Fe nutrition in the presence of insoluble Fe（OH）3. This suggests that aerobic rice could utilize Fe activated by PSw.

Selection of Inbred Lines for Breeding of Maize with High Efficiency in Iron Utilization

Crops are often subjected to iron(Fe)-deficiency due to the limited solubility of this essential element in most neutral or basic soils. Developing cultivars with high efficiency in Fe utilization via breeding programs can provide solutions to this problem as a long term strategy. In the present study, to select inbred lines for breeding of maize with high efficiency in Fe utilization, we screened 123 inbred lines at the seedling stage by analyzing secretion pattern of phytosiderophores, a class of non-protein amino acids released by graminaceous species for Fe utilization, using high-performance liquid chromatography. One hundred and twenty three inbred lines were clustered into nine groups. The low PS secretion rate under Fe-sufficient condition and high PS secretion rate increment after Fe-deficiency treatment type were the ideal inbred lines for breeding of maize with high efficiency in Fe utilization.

Transporters Contributing to Iron Trafficking in Plants

This review will discuss recent progress in understanding the many roles of transporters in the whole-plant physiological processes that maintain iron （Fe） homeostasis. These processes include uptake from the soil via roots, control of transport from roots to above-ground parts of the plant, unloading of Fe from the xylem in above-ground parts, loading of Fe into mitochondria and plastids, transport of Fe to reproductive parts of the plant, and Fe mobilization during seed germination. In addition, we will discuss the mechanisms that plants use to cope with an apparently unintended conse- quence of Fe acquisition： the uptake of toxic heavy metals via Fe transporters. Rapid progress has been made in under- standing the transport processes involved in each of these areas in the last 5 years and this review will focus on this recent progress. We will also highlight the key questions regarding transport steps that remain to be elucidated.