Our objectives were to determine the influence of salinity on root cell wall composition in soya beans and the possible mechanism of salt tolerance. Two soya bean cultivars, Touzan 69 (salt sensitive) and Dare (salt tolerant), were selected as experimental material for comparison. Root growth was clearly inhibited by salinity in both cultivars, but Touzan 69 showed more severe reductions in root length than Dare. In the 0–5 mm root segment (from root tip), the total cell wall sugar content of Touzan 69 decreased considerably due to salinity as were the pectin, hemicellulose and cellulose fractions. In Dare, NaCl treatments only caused a slight decrease in the pectin fraction and no marked change in hemicellulose and cellulose fractions. Without salt treatment, the pectin fraction accounted for about 40 % and cellulose for 30 % of cell wall composition in the 0–5 mm root segment; in the 5–10 segment (from root tip), pectin and cellulose accounted for 27 % and 45 % in Touzan 69, and 34 % and 38 % in Dare. The percentage of pectin decreased and that of cellulose increased in the 5–10 mm root segment compared with the 0–5 mm segment. This indicates that pectin largely regulates cell growth, as the 0–5 mm region is considered the elongation zone of soya bean roots. Salt treatment decreased the percentage of pectin, but increased that of cellulose across root zones of the two cultivars, suggesting that salt presence may increase cell wall rigidity, and thus, inhibits root growth. Dare was able to maintain its main root cell wall substances, an apparent advantage for root cell growth that may overall improve its salt tolerance. Also, the less reduction in cell wall uronic acid was of some benefit in the positive regulation of root cell growth in Dare. The changes in cell wall composition, especially the pectin content had a close relation with the regulation of root growth. The difference in salt tolerance between the two tested cultivars can partly be explained on the basis of these changes in response to salinity. Sugar compounds in each cell wall constituent and their functions in ion transport as well as the relationship between root cell wall and soya bean salt tolerance need to be further investigated.

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The accidentally introduced beetle Ophraella communa was first found in 1996 in Japan and has rapidly expanded its distribution range to include regions with substantially different climates. During this range expansion and subsequent establishment in new habitats, the life history traits of O. communa have changed depending on new habitat environmental conditions. In this study, we investigated the photoperiodic response of O. communa controlling its reproductive diapause, an important trait that adjusts the life cycle to local climate and phenology of host‐plants. We examined temporal changes and geographical differences in this trait. In the Tsukuba population of O. communa, the diapause incidence under conditions of 12 h light : 12 h dark (LD 12:12), 13:11 and 14:10 did not consistently increase or decrease during 2005–2012, although it fluctuated yearly. The diapause incidence in this period, however, was lower than that in 1999 reported previously and the critical day‐length inducing diapause was shortened by >1 h from 1999 to 2005. These results suggest that the photoperiodic response of O. communa shifted during this period. To examine geographical differences in this trait, we compared the Hirosaki, Morioka, Tsukuba and Koshi lines. The diapause incidence at LD 13:11 was significantly different between the O. communa lines: 86.5% in the Hirosaki line (collected in 2010) , 81.4% in Morioka (collected in 2010), 45.0% in Tsukuba (collected in 2011) and 7.1% in Koshi (collected in 2009), and was positively correlated with the latitude of the origin. These results suggest that this trait shifted, responding to the environmental conditions in the colonized regions.

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