The purpose of this research was to identify the soil organic matter (SOM) fractions changes in a crop rotation system under no-till system (NTS). This research was carried out from October 2010 to February 2014 in a Rhodic Hapludox. The experiment was set up in completely randomized blocks in a factorial design with eight cover crops and three soil depths (0-5, 5-10 and 10-20 cm) with four repetitions. Cover crops: fall-winter corn, intercropping fall-winter corn with Brachiaria ruziziensis, intercropping fall-winter corn with B. brizantha cv. Marandu, intercropping fall-winter corn with Crotalaria spectabilis, B. ruziziensis, B. brizantha cv. Marandu, Pennisetum glaucum L. and set-aside area. The results of SOM granulometric fractionation showed that 6.5% of the total organic carbon (TOC) stocks were in the particulate organic carbon (POC) fraction. The low values of POC observed in this research are associated with the weather condition of experimental site, which shows high temperature and moisture. In relation to the labile carbon (LC), the highest LC stock was observed in 0-5 cm depth, which differed from the 10-20 cm depth. The POC, LC and labile nitrogen (LN) were the SOM fractions that showed to be more sensitive to detect the changes promoted by the cover crops and soil depths in NTS, as well as the carbon management index (CMI). The intercropping fall-winter corn with B. brizantha cv. Marandu and B. ruziziensis were efficient in increasing the CMI in deeper depth (10-20 cm).
Dipteryx alata Vogel is a tree species widely found in Cerrado, settling preferentially in well drained soils. Studies related to ecophysiology of D. alata may contribute to the decision making about using seedlings of this species in projects aimed at the recovery of degraded areas where seasonal flooding happens. This study aimed to assess the effects of flooding on photosynthetic and antioxidant metabolism and quality of D. alata seedlings cultivated or not under flooding during four assessment periods (0, 20, 40, and 60 days), followed by 100 days after the end of each assessment period (0+100, 20+100, 40+100, and 60+100 days), allowing verifying the potential for post-flooding recovery. Flooded plants showed lower photosynthetic efficiency than non-flooded plants, regardless of the periods of exposure. However, this efficiency was recovered in the post-flooding, with values similar to that of the non-flooded seedlings. Moreover, the damage to FV/FM was evidenced by an increase in the period of exposure to flooding, but recovery was also observed at this stage of the photosynthetic metabolism. Seedling quality decreased under flooding, not varying between periods of exposure, but remained lower although the increase observed in the post-flooding period, with no recovery after flooding. The occurrence of hypertrophied lenticels associated with physiological changes and an efficient antioxidant enzyme system might have contributed to the survival and recovery of these seedlings. Thus, this species is sensitive to flooding stress but capable of adjusting and recovering metabolic characteristics at 100 days after the suspension of the water stress, but with no recovery in seedling quality. Thus, we suggested plasticity under the cultivation condition and determined that the time of 100 days is not enough for the complete resumption of growth.
The purpose of this study was to assess the changes in soil chemical properties affected by the cover crops cultivated in crop rotation in short-term of no-till implementation under Rhodic Hapludox soil. This research was carried out from October 2010 to February 2014. The experiment was set up in completely randomized blocks in a factorial design with eight treatments (cover crops) and three soil depths (0-5, 5-10 and 10-20 cm) with four repetitions. The cover crops were: fall-winter maize (T 1), intercropping fall-winter maize with B. ruziziensis (T 2), intercropping fall-winter maize with B. brizantha cv. Marandu (T 3), intercropping fall-winter maize with Crotalaria spectabilis (T 4), B. ruziziensis (T 5), B. brizantha cv. Marandu (T 6), Pennisetum glaucum L. (T 7) and fallow (T 8). The T 6 and T 7 affected exchangeable Mg +2 , it was observed higher exchangeable Mg +2 in T 6 (2.39 cmol c dm-3) and T 7 (2.43 cmol c dm-3) in comparison to T 1. The phosphorus content showed interactive effect between cover crops and soil depth. In the comparison among the depths, the P contents were higher in 5-10 cm, which showed improvement of 24.6% and 25.2% in comparison to 0-5 and 10-20 cm layers, respectively. The cover crops evaluated in this research affected the exchangeable Mg +2 and K + , as well as Mg +2 and K + saturation. The P content changed in response of cover crops, which was important to observe that this nutrient may increase the content with adoption of cover crops in no-till system. The species used in this research might be recommended to integrate a crop rotation system with the possibility of increasing P availability in topsoil depth in no-till system.
In this research it was hypothesized that Campomanesia xanthocarpa can overcome some level of water deficiency by adjusting physiological parameters and that shading minimizes the water deficit effects while maintaining elevated photosynthetic rates and relative water content of the leaves and makes a resumption of metabolism and growth when the water supply is normalized. The seedlings were submitted to two water regimes (continuous irrigation - CI and intermittent irrigation - II), three shading percentages (0, 30 and 70%) and six evaluation times (Start - T0, 1st Photosynthesis Zero - 1st P0, 1st Recovery - 1st REC, 2nd Photosynthesis Zero - 2nd P0, 2nd Recovery - 2nd REC and END). Plants under water deficit at 0% shading led to a reduction in photosynthetic metabolism, relative water content (RWC), leaf area, number of leaves, and height, especially during the stress periods 1st and 2nd P0. The 30 and 70% shading mitigated the stressful effect of water deficit on C. xanthocarpa seedlings. The results did not confirm the hypothesis that C. xanthocarpa seedlings are intolerant to water deficit since, although sensitive, they presented a potential for recovery of photosynthetic and growth characteristics under all cultivation conditions. It was concluded that that shading minimizes the stressful effects of water deficit.
This study aimed to evaluate the effect of exogenous application of salicylic acid on the photosynthetic metabolism and quality of Eugenia myrcianthes seedlings under water deficit and their recovery potential after rehydration. Two water regimes were evaluated, as follows: control - plants irrigated daily (I) and water deficit (S), with and without the application of 400 mg L–1 of salicylic acid (SA), totaling four treatments. Seedlings were evaluated at three times: at the beginning of the experiment (T0), that is, when the irrigation was interrupted; when the photosynthetic rate reached values close to zero (P0 - 15 days after irrigation interruption), that is, when irrigation restarted; and when the photosynthetic rate was recovered (REC). Eugenia myrcianthes seedlings were negatively affected when subjected to water restriction; salicylic acid attenuated the damage to the photosynthetic apparatus by acting positively on the relative water content in the leaves, SPAD index, photosynthetic metabolism, superoxide dismutase and peroxidase enzyme activity, and seedling growth in P0. Eugenia myrchiantes presented potential for recovery after resumption irrigation. The application of SA contributed to the maintenance of gas exchanges, photochemical processes and quality of E. myrcianthes seedlings during and after water deficit, suggesting the promotion of plant resistance induction.
The implantation of sweet sorghum has been shown as viable alternative in crop rotation in sugar cane plantation reform areas. The seed environment in the field is complex and several factors, such as different genotypes and osmotic stress, can negatively influence the seeds water uptake and, therefore, the sequence of germination events can be compromised. In this context, the objective of this study was to evaluate the different physiological responses of sweet sorghum seeds (Sorghum bicolor (L.) Moench) belonging to the hybrids CV 007 and CV 147 and cultivar BRS 506 when submitted to substrates with different water potentials (−0.1, −0.2, −0.3, −0.4, and −0.5 MPa) using solutions of polyethylene glycol (PEG 6000). The seeds remained in Biochemical Oxygen Demand-type germination chambers, under constant white light and the temperature of 25˚C for 14 h in the high temperature and 10 h in the low temperature. The moisture of the substrates was regularly monitored. The physiological potential of the genotypes was evaluated using the following characteristics: first count, germination, germination speed index (GSI), root length, and fresh and dry weights of seedlings. In general, germination and early growth of seedlings were negatively affected by the reduction of water potentials below −0.1 MPa, which was also damaging to the GSI of the seeds. Germination and growth of seedlings of the hybrids CV 007 and CV 147 and of the cultivar BRS 506 were affected by reduced water potentials starting at −0.1 MPa. The seeds of hybrid CV 147 were more tolerant to simulated water stress with PEG 6000 than those of hybrid CV 007 and cultivar BRS 506.
Allophylus edulis (A.St.-Hil., Cambess. and A. Juss.) Radlk., commonly known as cocum, belongs to the Sapindaceae family. This species is of great medicinal interest, with studies showing that its fruits have antioxidant, anti-cholinesterase, and cytotoxic activity. In addition, it is used in traditional medicine as an antidiarrheal, anti-inflammatory and antihypertensive. The objective of this study was to perform somatic embryogenesis in vitro from leaf and root explants of Allophylus edulis, using different 6-benzylaminopurine (BAP) concentrations combined with naphthalene acetic acid (NAA). All treatments exhibited 100% callus formation, except for the treatment without supplementation of growth regulators. The calluses developed in treatments from leaf explants showed up to two colors (brown and brown/cream), and the highest fresh and dry mass was observed in the treatment with 0.5 mg L-1 of BAP with 0.1 mg L-1 of NAA. There was no shoot formation from the leaf explants. The callogenesis in treatments from root segments showed callus formation with up to three colors (brown, brown/cream, and cream/green), and the highest fresh and dry mass was obtained when cultivated with 2.0 mg L-1 of BAP combined with 0.1 mg L-1 of NAA. These auxin and cytokinin concentrations also showed a higher number of shoots. The interaction between auxin and cytokinin is recommended to obtain somatic embryogenesis in root segments and callus with morphological characteristics suitable for organogenesis. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********
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