Vegetative growth after flowering through gibberellin biosynthesis regulates pod setting rate in soybean (Glycine max (L.) Merr.).

Pod setting rate in soybean is an important trait that determines pod number, which is highly correlated with seed yield. Using two soybean cultivars with different pod setting rates, we examined the relationship between plant growth regulation by gibberellin (GA) and pod setting rate. Plant growth rate (PGR) after flowering was significantly higher in 'Fukuyutaka' (low pod setting rate) than in 'Kariyutaka' (high pod setting rate); this difference was caused by increasing of GA biosynthesis-related genes expression. Additionally, pod setting rate in 'Fukuyutaka' was lower than that in 'Kariyutaka'. Furthermore, when 'Kariyutaka' was treated with GA after flowering, the PGR increased and pod setting rate decreased. These results suggest that pod setting rate in soybean is regulated by vegetative growth after flowering through GA biosynthesis.

Cold hardiness in various organs and tissues of Rhododendron species and the supercooling ability of flower buds as the most susceptible organ.

The freezing resistance of various organs and tissues was determined in 24 Rhododendron species (mainly Subgenus Tsutsutsi) having different ecological distributions. The order of hardiness for organ or tissue is as follows: leaf bud greater than wood greater than or equal to bark greater than flower bud, and the flower bud is characterized as the most cold-susceptible organ. The relationship of killing temperature (KT) to northern distribution was the most significant in leaf buds compared to other organs and tissues. KTs of leaf buds for the most hardy species were -45 degrees C (or below) and those for the most tender species were about -23 degrees C, while KTs of flower buds were about -28 degrees C for the former and -16 degrees C for the latter. Although KTs of flower buds native to southwestern Japan were well correlated with the exothermic temperature distribution (ETD) of florets, those in the more northern species were generally lower than ETDs. The supercooling ability of flower buds appears to be sufficient to avoid the freezing stress since the extreme minimum temperature (EMT) at the northern limit of natural distribution for each tree species examined was not lower than the KT and ETD of the flower buds.