ABSTRACT The aim of the present study was to determine the beekeeping potential of Croton heliotropiifolius Kunth (Euphorbiaceae) based on flowering strategy, floral characteristics, available floral resources, and the individuals frequencies and foraging activities of Apis mellifera L. on its flowers in Fazenda Ingazeira, Brazil. Each C. heliotropiifolius plant possessed inconspicuous diclinous flowers clustered into 560 ± 60 dense terminal inflorescences containing 59 ± 12 pistillate and 160 ± 26 staminate flowers. Although both types of flowers produced nectar (pistillate: 2.8 ± 0.8 μL ; staminate: 0.3 ± 0.06 μL ), A. mellifera workers mostly visited staminate flowers (98%) during the peak visitation period (08:00-11:00 h). Moreover, during the foraging period, each plant produced approximately 5.376 × 10 8 pollen grains, ensuring approximately 33 visitation cycles from a colony of A mellifera workers that picked up an average of 405 pollen grains per visit per flower. Further, C. heliotropiifolius showed an annual cornucopia flowering strategy with high flower production for five months, which is an important characteristic that ensures floral resource availability in the environment. These findings suggest that C. heliotropiifolius has a great potential for apiculture in this region.

ABSTRACT Yellow passion fruit is a fruit species widely cultivated throughout the Brazilian semi-arid territory, but its yield is affected by the quality of the waters of this region. In this context, the objective was to evaluate the gas exchange and production of passion fruit cv. BRS Rubi do Cerrado irrigated with waters of different cationic natures. The study was conducted in drainage lysimeters under greenhouse conditions in Campina Grande, PB, Brazil, in a randomized block design, and the treatments were eight cationic natures of irrigation water (S1 - Control; S2 - Na+; S3 - Ca2+; S4 - Mg2+; S5 - Na+ + Ca2+; S6 - Na+ + Mg2+; S7 - Ca2+ + Mg2+ and S8 - Na+ + Ca2+ + Mg2+) with three replicates. Plants in the control treatment were irrigated with water of low electrical conductivity (ECw = 0.4 dS m-1), while those of the other treatments were irrigated using water with ECw of 3.5 dS m-1. The treatments Na+ + Ca2+, Na+ + Mg2+ and Ca2+ + Mg2+ were prepared in the equivalent ratio of 1:1, and Na++Ca2++Mg2+ in the ratio 7:2:1, respectively. Water salinity of 3.5 dS m-1 reduced gas exchange, and stomatal conductance and transpiration were the most sensitive variables of passion fruit. The number of fruits of passion fruit cv. BRS Rubi do Cerrado decreased with water salinity, regardless of the cationic nature. The waters of calcic and calcic+magnesian nature caused the greatest deleterious effects on the production variables of passion fruit, at 259 days after transplanting.

ABSTRACT Due to the predictions of climate change, there is a need to identify forage plants that can keep their productivity and nutritive value under hydric stress. The objective of this study was to evaluate the biomass and chemical responses of three Desmanthus spp. accessions under two water deprivation regimens (7 and 21-day). The experimental design used was randomized blocks in a 3 × 2 factorial arrangement (access and water deprivation) with four replications. There were reductions in the biomasses of leaf and stem fractions of 64% and 51%, respectively. The 43F accession showed greater leaf (1.86 g.plant-1) and stem (1.97 g.plant-1) biomasses under a total water restriction of 21 days, compared to the 89F and AusT accessions. In accessions 43F and 89F, there were carbohydrate accumulations in the leaves of 28% and 51%, respectively, under the 21-day water restriction, while AusT decreased 38% within a 7-day interval. Water deprivation affected the chemical characteristics of the accessions. Free proline was similar among accessions and accumulated 463% more in the leaves of plants submitted to 21-day water deprivation (90.22 mg.kg-1) compared to those subjected to water deprivation for 7 days (16.03 mg.kg-1). Proline and total soluble carbohydrate accumulation in 43F and 89F were insufficient to regulate crude protein, C content, and C:N ratios. These results demonstrate the variability in drought tolerance among accessions. Accessions 43F and 89F were more susceptible to 21-day water deprivation, while AusT showed greater drought tolerance.

ABSTRACT The biological control, thinking about the integrated management, has been inserted with other management techniques to disease control, such as soybean anthracnose. The aims of this work were to verify the action of Trichoderma and Bacillus isolates in the induction of soybean resistance mechanisms to anthracnose as a function of seed treatment. The statistical design was entirely randomised, in a 5 x 2 (agent species x sampling times) factorial scheme with five replicates. Soybean seeds were treated with Bacillus amyloliquefaciens BV03, B. subtilis BV02, Trichoderma asperellum BV10, Carbendazim + Thiram and distilled water (control). Seven days after seedling emergence, 2 μL of 1 x 10−4 Colletotrichum truncatum spores were inoculated on the cotyledons. Catalase (CAT), peroxidase (POX), phenylalanine ammonia lyase (PAL) and glyceollin (GLY) activities before and after pathogen inoculation, as well as the diameter of the anthracnose lesion on the cotyledons, were evaluated. Data were submitted to analysis of variance and, when significant, the mean values were compared by Fisher’s test (p < 0.05). The treatments did not influence the first sampling time before inoculation. Trichoderma asperellum BV10 increased POX and PAL activities up to 173%, while B. amyloliquefaciens BV03 increased POX activity. Glyceollin was not influenced by the treatments. The T. asperellum BV10 reduces the diameter of the anthracnose lesion by up to 61%. Thus, T. asperellum BV10 has the potential to control soybean anthracnose, improved the response defense against C. truncatum, when performed on seed treatment.

ABSTRACT The action of photosystem I (PSI) inhibiting herbicides depends on light to cause oxidative stress in plants. However, their translocation is inhibited due to their rapid action in the presence of light. The aim was to evaluate the efficacy of the herbicide diquat for control of corn plants subjected to different periods of absence of light after application. Two experiments (field and greenhouse) were conducted, applying the herbicide diquat (200 g a.i. ha−1) to maize plants at stage V4. The plants were subjected to different periods of absence of light after diquat application: 0; 1; 2; 3; 4; 5 and 6 hours. A treatment without herbicide application was used as a control. The control (%) and biomass of corn plants were evaluated in both experiments, and photosynthetic activity and hydrogen peroxide (H2O2) accumulation in leaves were evaluated in the greenhouse experiment. The results showed that diquat needs at least 5 hours of absence of light after application to fully control corn plants. The plants recovered when using shorter periods (4 hours or less) of darkness, and injuries were restricted to points where the herbicide had contact with the plant. The ability of plants to recover was related to the higher photosynthetic activity and oxidative stress induction due to early light exposure. Thus, the lower production of H2O2 in plants kept in the dark for longer periods after herbicide application allows the translocation of the herbicide to meristems, which prevents regrowth of corn plants.

ABSTRACT The possibility of early soybean fertilization carried out on the predecessor crop has several benefits, mainly operational ones, making the production system more conservationist and balanced. An experiment was carried out at the Anhumas Experimental Station, Luiz de Queiroz College of Agriculture (USP/ESALQ), located in Piracicaba, SP, Brazil, during 2001/2002, 2002/2003, and 2003/2004 agricultural years on a typic Hapludox aiming to evaluate the effects of the early fertilization on soybean yield. The fertilization consisted of applying 90 kg ha−1 of P2O5, 50 kg ha−1 of K2O, and micronutrients (Co, Cu, Fe, Mn, Mo, and Zn). The experiment was conducted in a randomized complete block design with three replications and 12 treatments consisting of different levels of early soybean fertilization carried out on the finger millet crop: T1, no fertilization; T2, conventional soybean fertilization; T3, early 50% K fertilization; T4, early 100% K fertilization; T5, early 50% P fertilization; T6, early 50% P and K fertilization; T7, early 50% P and 100% K fertilization; T8, early 100% P fertilization; T9, early 100% P and 50% K fertilization; T10, early 100% P and K fertilization; T11, early 100% P and K fertilization + micronutrients; and T12, early leaf fertilization with micronutrients. The results showed that the early soybean sowing fertilization with phosphorus and potassium carried out during finger millet sowing does not interfere with the thousand-seed weight and soybean yield.

ABSTRACT Specific cultivars for production of green corn, more productive and adapted to the conditions of each region, combined with adequate population density, can increase the yield of the crop. This work aimed to identify, under different plant densities, the cultivars with agronomic characteristics for the production of green corn. The experiment was conducted from March to June 2018, in the experimental area of the Technical College of Teresina, at the Federal University of Piauí. The treatments were distributed in a randomized block design, in a factorial scheme, with three plant densities (40,000, 50,000 and 60,000 plants ha−1) and two corn cultivars (AG 1051 and BRS 3046). The variables evaluated were the diameter and length of the commercial green ear, the yield, the percentage of commercial green ear and the length of the period between the emergence (VE) and the flowering stage (VT) of the cultivars in relation to the accumulated number of degree-days (ADD). In terms of cycle (period between VE and VT), the hybrid AG 1051 was later, with 47 days after emergence (DAE) and 823.23 ADD, than the BRS 3046 (44 DAE and 773.32 ADD); however, there was an acceleration of the period of vegetative development in the hybrids, which ranged from 43 (773.32 ADD) to 47 (828.23 ADD) days, respectively, so that there was male flowering. With the increase in densities, there was decrease in the values of production. The highest yield of commercial ears (15.45 Mg ha-1) was obtained at a density of 50,000 plants ha−1.

ABSTRACT The invasive pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), is a pest that threatens the production of fruits, vegetable, and ornamental plants in Brazil. It is a phytophagous insect with a wide range of hosts; thus, there is an increasing demand for sustainable environmental-friendly control methods, such as biological control. This study aimed to investigate biological parameters of Ceraeochrysa everes (Neuroptera: Chrysopidae) fed on 2nd instar nymphs of M. hirsutus and eggs of Ephestia (Anagasta) kuehniella (Zeller) (Lepidoptera: Pyralidae). The duration of the immature stages of C. everes was longer when the predator was fed on 2nd instar nymphs of M. hirsutus, compared to the control (E. kuehniella). The survival rate of immature C. everes was 82.5% and 100% when fed on 2nd instar nymphs of M. hirsutus and eggs of E. kuehniella, respectively. The type of food resource offered at the larval stage affected the pre-oviposition, oviposition, and post-oviposition periods and the longevity of C. everes females. Adult females C. everes from immature individuals fed an exclusive diet of E. kuehniella eggs had longer oviposition, fecundity (daily and total), fertility, and post-oviposition periods and longevity. Ceraeochrysa everes has the capacity for predation, development, and reproduction while having 2nd instar nymphs of M. hirsutus as food resource. Therefore, C. everes has a promising potential for controlling M. hirsutus.

ABSTRACT Erythrina velutina Willd. (Fabaceae) is drought tolerant and has the potential for reforestation in the semi-arid region. The response of its seeds to the environmental conditions of each production area influences their size, weight, physiological potential, and health. Thus, this study aimed to assess how the environmental conditions of the different regions of Paraíba influence the biometric characteristics of E. velutina seeds. Seeds from 19 mother plants collected in Juru, Sumé, Araçagi, Guarabira, São João do Cariri, Esperança, Queimadas, Cuité, Boa Vista, and Areia, in the state of Paraíba, Brazil, were used in this study. Water content, thousand-seed weight, and biometric characteristics (length, width, and thickness) were determined in the seeds from each location. The water content ranged from 3.11 to 6.84%, while the thousand-seed weight was higher in mother plants grown in Sumé and Cuité. Seed length ranged from 9.00 to 16.84 mm, being higher in mother plants grown in Juru. Seed thickness and width ranged from 5 to 12.99 mm and were larger in mother plants from Cuité. Temperature, humidity, solar radiation, wind, and precipitation caused variations in the length, width, and thickness of E. velutina seeds, with higher means observed in mother plants grown in Cuité.

ABSTRACT Knowledge about the effect of chemical conditioners on the reduction of the deleterious effects caused by salinity on crops is of great importance for the expansion of the cultivation of vegetable crops such as zucchini in the semi-arid region of the Northeast. In this context, the objective of the present study was to evaluate the effect of the foliar application of hydrogen peroxide as a mitigator of salt stress on the gas exchange, production, and postharvest fruit quality of zucchini cultivated in a hydroponic system. The study was conducted in NFT-type (Nutrient Film Technique) hydroponic system in a greenhouse, in Pombal — PB, Brazil. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution - ECns (2.1 (control); 3.6; 5.1 and 6.6 dS m−1), and four concentrations of hydrogen peroxide - H2O2 (0; 20; 40 and 60 μM), with three replicates. Nutrient solution with electrical conductivity above 2.1 dS m−1 caused a reduction in gas exchange and the total number of fruits of zucchini. An increase in nutrient solution salinity levels increased the total soluble solids content of the fruits and the initial fluorescence of zucchini. Under conditions of nutrient solution salinity above 2.1 dS m−1, hydrogen peroxide could not mitigate the effects of salt stress. Application of 20 μM of H2O2 when the plants were grown in a nutrient solution of 2.1 dS m−1 promoted higher total fruit weight and basal diameter of the fruits.