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Auxin is a key hormone that regulates plant growth and development, including plant shape and sensitivity to environmental changes. Auxin is biosynthesized and metabolized via many parallel pathways, and it is sensed and transduced by both normal and atypical pathways. The production, catabolism, and signal transduction pathways of auxin primarily govern its role in plant growth and development, and in the response to stress. Recent research has discovered that auxin not only responds to intrinsic developmental signals, but also mediates various environmental signals (e.g., drought, heavy metals, and temperature stresses) and interacts with hormones such as cytokinin, abscisic acid, gibberellin, and ethylene, all of which are involved in the regulation of plant growth and development, as well as the maintenance of homeostatic equilibrium in plant cells. In this review, we discuss the latest research on auxin types, biosynthesis and metabolism, polar transport, signaling pathways, and interactions with other hormones. We also summarize the important role of auxin in plants under abiotic stresses. These discussions provide new perspectives to understand the molecular mechanisms of auxin's functions in plant development. [ABSTRACT FROM AUTHOR]

The main objective of this study was to compare the effects of two densities (278 stems x [ha.sup.-1] with two spacings of 6 m x 6 m or 4.5 m x 8 m, 400 stems x [ha.sup.-1] with two spacings of 5m x 5m or 3m x 8 m) and three poplar clones (NL95, NL895, and NL797) on productivity and carbon (C) sequestration of poplar ecosystems. The results showed that planting density significantly affected the biomass of a single tree. The mean tree biomass of clone NL95 was higher in all spacings than that of the other clones, with a significant difference for the 6 m x 6 m spacing. The biomass of poplar trees ranged from 78.9 to 110.3 Mg x [ha.sup.-1], with the highest tree biomass observed in the square configuration. Soil C concentration (0-100 cm) increased after 12 years of management. Soil C storage ranged from 138.1 to 164.3 Mg C x [ha.sup.-1], and the highest soil C storage was in the NL797 poplar plantation with 6 m x 6 m spacing. Our results suggested that clones NL95 and NL797 should be chosen for planting, with a planting density of 278 stems x [ha.sup.-1] and spacing of 6 m x 6 m. Key words: biomass production, C sequestration, plant density, plant spacing, poplar clone. Le principal objectif de cette etude etait de comparer les effets de deux densites (278 tiges * [ha.sup.-1] avec deux espacements de 6 m x 6 m ou 4,5 m x 8 m, 400 tiges x [ha.sup.-1] avec deux espacements de 5 m x 5 m ou 3 m x 8 m) et de trois clones de peuplier (NL95, NL895 et NL797) sur la productivite et la sequestration du carbone (C) dans les ecosystemes de peuplier. Les resultats montrent que la densite de plantation a eu un impact significatif sur un seul clone. La biomasse moyenne des tiges du clone NL95 etait plus elevee que celle des deux autres clones peu importe l'espacement et la difference etait significative pour l'espacement de 6 m x 6 m. La biomasse des tiges de peuplier variait de 78,9 a 110,3 Mg * [ha.sup.-1] et la biomasse la plus elevee a ete observee dans la configuration carree. La concentration de C dans le sol (0-100 cm) avait augmente apres 12 ans d'amenagement. L'entreposage de C dans le sol variait de 138,1 a 164,3 Mg C * [ha.sup.-1] et la quantite la plus elevee a ete observee dans la plantation du clone NL797 avec un espacement de 6 m x 6 m. Nos resultats indiquent que les clones NL95 et NL797 devraient etre retenus pour etre plantes avec une densite de 278 tiges x [ha.sup.-1] et un espacement de 6 m x 6 m. [Traduit par la Redaction] Mots-cles: production de biomasse, sequestration du C, densite des plants, espacement des plants, clone de peuplier., 1. Introduction The continuous increase in atmospheric carbon dioxide (C[O.sub.2]) concentration is the primary factor of climate change (Zhang et al. 2020). The two main causes of C[O.sub.2] increase are [...]

Land use significantly affects soil biological fertility through impacts on carbon (C) and nitrogen (N) cycling. The present study investigated the effects of long‐term rice cultivation after tidal flat reclamation on soil C and N metabolism, microbial biomass and biological fertility. Eighteen composite topsoil (0–20 cm) samples were identified in a chronosequence of coastal reclamation areas (0–700 years old) in subtropical monsoon climate zone, namely tidal flat (T0), salt marsh soil (S10) and paddy soil (P50, P100, P300 and P700). Using ANOVA analysis, mono‐exponential regression model, and multiple linear regressions, soil organic matter (SOM), total nitrogen (TN), cumulative C mineralization content (Ct) and N mineralization content (Nt), basal soil respiration (BSR) and microbial biomass C and N (MBC and MBN) in the P50‐P700 samples were significantly higher than those in the T0 and S10 samples, whereas C metabolic quotients (qCO2) in the P50‐P700 were significantly lower than those in the T0 and S10 samples. The time to steady state for SOM and TN are 357 years and 80 years, respectively; 133 and 221 years for Ct and Nt, respectively; and 318 and 183 years for MBC and MBN, respectively. Also, a soil biological fertility index (SBFI) was calculated on the basis of SOM, BSR, Ct, MBC, qCO2 and qCM. P100‐P300 samples had the highest SBFI score (28.7) and ranked in the class V (very high) of biological fertility, achieving steady‐state conditions after 146 years. SBFI was significantly positively correlated with SOM, TN, MBC, MBN, BSR, Ct and Nt, whereas it was significantly negatively correlated with pH, qCO2 and C mineralization quotient (qCM). MBC and qCM were two independent variables with considerable positive effects on SBFI. Long‐term rice cultivation could facilitate C and N accumulation and enhance biological fertility in soils via microbial activity, especially within 300 years. Our findings demonstrate that rice cultivation has the potential to enhance soil C and N accumulation. Carbon‐related SBFI is suitable for assessing soils under long‐term rice cultivation, mainly because the rice paddy field is an intensive and conservative system. [ABSTRACT FROM AUTHOR]