Summary: A dataset of 87 020 nifH reads and 16 782 unique nifH protein sequences obtained over 2 years from four locations across a gradient of agricultural soil types in A rgentina were analysed to provide a detailed and comprehensive picture of the diversity, abundance and responses of the N ₂ ‐fixing community in relation to differences in soil chemistry and agricultural practices. Phylogenetic analysis revealed an expected high proportion of A lphaproteobacteria , B etaproteobacteria and D eltaproteobacteria , mainly relatives to B radyrhizobium and M ethylosinus / M ethylocystis , but a surprising paucity of G ammaproteobacteria . Analysis of variance and stepwise regression modelling suggested location and treatment‐specific influences of soil type on diazotrophic community composition and organic carbon concentrations on nifH diversity. nifH gene abundance, determined by quantitative real‐time polymerase chain reaction, was higher in agricultural soils than in non‐agricultural soils, and was influenced by soil chemistry under intensive crop rotation but not under monoculture. At some locations, sustainable increased crop yields might be possible through the management of soil chemistry to improve the abundance and diversity of N ₂ ‐fixing bacteria.

In tomato, auxin and gibberellins (GAs) interact with each other to drive fruit growth and development. While the role of auxin in directing GA biosynthesis and signal is already known, very little information has been obtained about GA‐mediated control of auxin signalling and response. Interestingly, we show that gibberellic acid (GA₃) is able to modify the expression of several auxin signalling genes in the partial auxin‐insensitive diageotropica (dgt) mutant, suggesting that GAs may override the control of DGT on auxin signal. Procera (pro) mutation, which confers a constitutively active GA signal, enhances the effects of exogenous auxin, indicating that PRO may act as a negative effector of auxin responses in fruits. Indeed, transcript modulation of some auxin/indole acetic acid and auxin response factor genes in auxin‐treated dgt/pro fruits suggests that PRO controls their expression possibly bypassing DGT. It was also shown that GA biosynthesis, in response to auxin treatment, is largely controlled by DGT. It is therefore conceivable that the DGT‐mediated increase of active GAs in auxin‐treated or pollinated fruits would promote PRO degradation, which in turn activates part of the auxin signalling cascade.