Previous studies have shown that waterlogging/ hypoxic conditions induce aerenchyma formation to facilitate gas exchange. Ethylene (ET) and reactive oxygen species (ROS), as regulatory signals, might also be involved in these adaptive responses. However, the interrelationships between these signals have seldom been reported. Herein, we showed that programmed cell death (PCD) was involved in aerenchyma formation in the stem of Helianthus annuus. Lysigenous aerenchyma formation in the stem was induced through waterlogging (WA), ethylene and ROS. Pre-treatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) partially suppressed aerenchyma formation in the seedlings after treatment with WA, ET and 3-amino-1, 2, 4-triazole (AT, catalase inhibitor). In addition, pre-treatment with the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) partially suppressed aerenchyma formation induced through WA and ET in the seedlings, but barely inhibited aerenchyma formation induced through ROS. These results revealed that ethylene-mediated ROS signaling plays a role in aerenchyma formation, and there is a causal and interdependent relationship during WA, ET and ROS in PCD, which regulates signal networks in the stem of H. annuus.

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Solutions are urgently needed to address the continued degradation of agricultural soils worldwide, which has severely impacted the ability to grow crops and has led to increased irrigation demand from already rapidly depleting freshwater resources.This project evaluated a unique, previously untested, type of soil organic amendment, that is, coarse wood chips, for capturing and storing scarce precipitation and improving desertified, sandy soils. A field plot experiment was conducted in Ningxia, China, from 2011 through 2016, comparing unamended sandy soils with three coarse woody amendments, including (a) surface-applied mulch, (b) wood chips incorporated into the top 20 cm of soil, and 3) incorporated wood chips combined with a branch lattice shelter over the soil surface-all treatments replicated under both irrigated and nonirrigated conditions. Precipitation patterns and soil moisture content were compared between 2012 and 2015, and related soil physical and chemical properties were monitored continuously, as well as alfalfa yields in 2015 and 2016. Results indicated that amended soils maintained significantly higher soil water contents between rain events, decreased the number of days below the permanent wilting point, and improved soil properties and alfalfa growth. The combination treatment of wood chips and a branch shelter performed the best among treatments, exhibiting increases in average water storage 50% or more above controls. Unlike highly degradable soil amendments, the slow decomposition of the coarse wood chips resulted in continuous benefits for all 5 years. This use of coarse wood chips represents a timely new addition to the toolbox of soil amendments, providing a mechanism for immediate, long-lasting restoration of the world's degraded and desertified soils that will foster global food and water security.

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