Legume cultivars affect N uptake, component crop growth, and soil physical and chemical characteristics in maize–legume intercropping systems.  However, how belowground interactions mediate root growth, N fixation, and nodulation of different legumes to affect N uptake is still unclear.  Hence, a two-year experiment was conducted with five planting patterns, i.e., maize–soybean strip intercropping (IMS), maize–peanut strip intercropping (IMP), and corresponding monocultures (monoculture maize (MM), monoculture soybean (MS), and monoculture peanut (MP)), and two N application rates, i.e., no N fertilizer (N–) and conventional N fertilizer (N+), to examine relationships between N uptake and root distribution of crops, legume nodulation and soil N availability.  Results showed that the averaged N uptake per unit area of intercrops was significantly lower than the corresponding monocultures.  Compared with the monoculture system, the N uptake of the intercropping systems increased by 31.7–45.4% in IMS and by 7.4–12.2% in IMP, respectively.  The N uptake per plant of intercropped maize and soybean significantly increased by 61.6 and 31.8%, and that of intercropped peanuts significantly decreased by 46.6% compared with the corresponding monocultures.  Maize and soybean showed asymmetrical distribution of roots in strip intercropping systems.  The root length density (RLD) and root surface area density (RSAD) of intercropped maize and soybean were significantly greater than that of the corresponding monocultures.  The roots of intercropped peanuts were confined, which resulted in decreased RLD and RSAD compared with the monoculture.  The nodule number and nodule fresh weight of soybean were significantly greater in IMS than in MS, and those of peanut were significantly lower in IMP than in MP.  The soil protease, urease, and nitrate reductase activities of maize and soybean were significantly greater in IMS and IMP than in the corresponding monoculture, while the enzyme activities of peanut were significantly lower in IMP than in MP.  The soil available N of maize and soybean was significantly greater increased in IMS and IMP than in the corresponding monocultures, while that of IMP was significantly lower than in MP.  In summary, the IMS system was more beneficial to N uptake than the IMP system.  The intercropping of maize and legumes can promote the N uptake of maize, thus reducing the need for N application and improving agricultural sustainability.

The jasmonate ZIM domain (JAZ) protein belongs to the TIFY ((TIF[F/Y]XG) domain protein) family, which is composed of several plant-specific proteins that play important roles in plant growth, development, and defense responses.  However, the mechanism of the sorghum JAZ family in response to abiotic stress remains unclear.  In the present study, a total of 17 JAZ genes were identified in sorghum using a Hidden Markov Model search.  In addition, real-time quantification polymerase chain reaction (RT-qPCR) was used to analyze the gene expression patterns under abiotic stress.  Based on phylogenetic tree analysis, the sorghum JAZ proteins were mainly divided into nine subfamilies.  A promoter analysis revealed that the SbJAZ family contains diverse types of promoter cis-acting elements, indicating that JAZ proteins function in multiple pathways upon stress stimulation in plants.  According to RT-qPCR, SbJAZ gene expression is tissue-specific.  Additionally, under cold, hot, polyethylene glycol, jasmonic acid, abscisic acid, and gibberellin treatments, the expression patterns of SbJAZ genes were distinctly different, indicating that the expression of SbJAZ genes may be coordinated with different stresses.  Furthermore, the overexpression of SbJAZ1 in Escherichia coli was found to promote the growth of recombinant cells under abiotic stresses, such as PEG 6000, NaCl, and 40°C treatments.  Altogether, our findings help us to better understand the potential molecular mechanisms of the SbJAZ family in sorghum in response to abiotic stresses.

In China, the abuse of chemical nitrogen (N) fertilizer results in decreasing N use efficiency (NUE), wasting resources and causing serious environmental problems.  Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China.  To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system (IMS).  Three N rates, NN (no nitrogen application), LN (lower N application: 270 kg N ha^–1), and CN (conventional N application: 330 kg N ha^–1), and three topdressing distances of LN (LND), e.g., 15 cm (LND1), 30 cm (LND2) and 45 cm (LND3) from maize rows were evaluated.  At the beginning seed stage (R5), the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant^–1 and 0.14 mL h^–1 plant^–1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively.  The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3.  The N uptake, NUE and N agronomy efficiency (NAE) of IMS under CN were 308.3 kg ha^–1, 28.5%, and 5.7 kg grain kg^–1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively.  The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively.  Those results suggested that LN with distances of 15–30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping.  Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.

Potassium (K) deficiency is one of the major abiotic stresses which has drastically influenced maize growth and yield around the world. However, the physiological mechanism of K deficiency tolerance is not yet fully understood. To identify the differences of root morphology, physiology and endogenous hormones at different growing stages, two maize inbred lines 90-21-3 (tolerance to K deficiency) and D937 (sensitive to K deficiency) were cultivated in the long-term K fertilizer experimental pool under high potassium (+K) and low potassium (–K) treatments. The results indicated that the root length, volume and surface area of 90-21-3 were significantly higher than those of D937 under –K treatment at different growing stages. It was noteworthy that the lateral roots of 90-21-3 were dramatically higher than those of D937 at tasselling and flowering stage under –K treatment. Meanwhile, the values of superoxide dismutase (SOD) and oxidizing force of 90-21-3 were apparently higher than those of D937, whereas malondialdehyde (MDA) content of D937 was obviously increased. Compared with +K treatment, the indole-3-acetic acid (IAA) content of 90-21-3 was largely increased under –K treatment, whereas it was sharply decreased in D937. On the contrary, abscisic acid (ABA) content of 90-21-3 was slightly increased, but that of D937 was significantly increased. The zeatin riboside (ZR) content of 90-21-3 was significantly decreased, while that of D937 was relatively increased. These results indicated that the endogenous hormones were stimulated in 90-21-3 to adjust lateral root development and to maintain the physiology function thereby alleviating K deficiency.