Silicon and salicylic acid promote different responses in legume plants

Abstract

The foliar application of silicon (Si) and salicylic acid (SA) can be beneficial to plants. However, there are doubts about the interaction of Si and SA in the physiology and yield of legume crop. The objective of this study was to evaluate the effects of foliar application of Si and SA on the photosynthetic variables and yield of soybean and bean grains. The experiments were composed by four treatments: potassium silicate and stabilized sodium at a concentration of 3.6?g?L^?1 Si in the absence and presence of SA (210?mg?L^?1), only SA, and without Si or SA. The interaction of Si with foliar SA enhanced photosynthesis only in soybean; it did not affect the physiological variables of bean and did not alter the yield of the two crops. The results indicated that foliar Si application at high concentrations, independently of SA application, increased the physiological variables of the soybean without affecting the yield; however, the combined application of Si and SA had an adverse effect on the physiology and yield of bean.     

SOURCES OF SULFUR FOR DRY MATTER,SEED YIELD,AND OIL CONCENTRATION OF CANOLA GROWN IN SULFUR DEFICIENT SOILS OF SOUTH-WESTERN AUSTRALIA

Leaching of sulfur (S) on sandy soils may limit the effectiveness of S fertilizers especially when applied at sowing. The effectiveness of S sources for canola (oil seed rape, Brassica napus L.) grown in sandy low S soils of south-western Australia is not known. This study was completed to determine the relative effectiveness of gypsum and a gypsum-based by-product from synthetic rutile processing called Canola Blue for canola grown in low S soils of the region. Canola Blue is a mixture of gypsum and elemental S, and is granulated so its effectiveness may vary from gypsum. We measured the effectiveness of the two S sources in the glasshouse for young seedling growth and for minimizing S leaching. In the four field experiments, the two S sources were evaluated for relative effects on canola seed yield and the concentration of oil in seed. Canola Blue applied at sowing was as effective as gypsum for canola growth in the glasshouse and when applied at 35 days after sowing (DAS) was as effective as gypsum for seed yield in the field. For the glasshouse study, Canola Blue when applied to the soil surface (topdressed) at 35 DAS was as effective as gypsum in achieving a rapid recovery of leaves from S deficiency symptoms and of shoot growth. Where S deficiency appears during the growing season, topdressing with Canola Blue appears to be as effective under the conditions of this experiment as was gypsum. However, the S in Canola Blue was less prone to leaching than that applied as gypsum.     

Antigenotoxicity and Antioxidant Activity of Acerola Fruit (Malpighia glabra L.) at Two Stages of Ripeness

Genotoxic and antigenotoxic effects of acerola fruit at two stages of ripeness were investigated using mice blood cells. The results show that no ripeness stage of acerola extracts presented any genotoxic potential to damage DNA (Comet assay) or cytotoxicity (MTT assay). When antigenotoxic activity was analyzed, unripe fruit presented higher DNA protection than ripe fruit (red color) extract. The antioxidant capacity of substances also showed that unripe samples inhibit the free radical DPPH more significantly than the ripe ones. The results about determination of compounds made using HPLC showed that unripe acerola presents higher levels of vitamin C as compared to ripe acerola. Thus, vitamin C and the complex mixture of nutrients of Malpighia glabra L., and especially its ripeness stages, influenced the interaction of the fruit extract with the DNA. Acerola is usually consumed when ripe (red fruit), although it is the green fruit (unripe) that has higher potential as beneficial to DNA, protecting it against oxidative stress.     

The role of soil factors and leaf protein in the utilization of mopane plants by elephants in northern Botswana

Background  

Mopane (Colophospermum mopane) plants form monotypic woodlands that cover extensive areas in northern Botswana. Mopane is also a principal food item in the diet of elephants. Obtrusive damage to mopane plants as a result of elephant feeding may alter the structure of mopane woodlands. Some mopane woodland areas in northern Botswana are subjected to heavy elephant utilization rates whereas other mopane areas are less affected. However, the underlying reason for the concentrated elephant utilization is unknown.     

Nanoparticles in the management of brown eye spot in coffee

European Journal of Plant Pathology - Brown eye spot (Cercospora coffeicola) is one of the main diseases of coffee (Coffea arabica L.) and represents a serious phytosanitary problem for the crop....     

Soil physico-chemical properties,biomass production,and root density in a green manure farming system from tropical ecosystem,North-eastern Brazil

Purpose

Soil physico-chemical properties, biomass production, and root density are considered key factors indicating soil health in an agroecosystem. The soil physico-chemical changes and plant growth (e.g., shoot biomass production and root density) in a 6-year cultivation of plant species used as green manure in a sandy soil from Tropical ecosystem, North-eastern Brazil, were investigated between July and December 2019.

Material and methods

We characterized soil physical and chemical properties, shoot biomass production, and root density under ten plant species used as green manure: Brachiaria decumbens Stapf. cv. Basilisk, Canavalia ensiformis (L.) DC, Crotalaria juncea L., Crotalaria ochroleuca G. Don, Crotalaria spectabilis Roth, Lablab purpureus (L.) Sweet, Mucuna pruriens (L.) DC, Neonotonia wightii (Wight & Arn.) J.A. Lackey, Pennisetum glaucum L., and Stilozobium aterrimum Piper and Tracy.

Results and discussion

The highest values of soil pH, exchangeable cations, CEC, and soil available water capacity were found on the plots where Poaceae plants were cultivated, whereas for H⁺+Al³⁺, C.E.C., soil available water, and soil available water capacity were found on the plots where Fabaceae plants were cultivated. On the plots where C. ensiformis and N. wightii were cultivated, we found the highest shoot dry biomass and root density, respectively. The results highlight the importance to consider plant species from both Poaceae and Fabaceae family used as green manure as soil conditioner (by promoting soil fertility, nutrient cycling, and hydraulic properties into plant root zone), and thus creating a positive plant-soil feedback.

Conclusions

Our findings suggest that (1) a consecutive green manure practice without any input of fertilizers after 6 years changed positively both soil physical and chemical properties, and improve plant growth (e.g., shoot dry biomass and root density) in tropical savanna climate conditions; and (2) by altering soil fertility, both Poaceae and Fabaceae plants used as green manure may create a sustainable cycle into the soil profile thus promoting soil health.

     

Temporal dynamics of stem expansion and contraction in savanna trees: withdrawal and recharge of stored water

Relationships between diel changes in stem expansion and contraction and discharge and refilling of stem water storage tissues were studied in six dominant Neotropical savanna (cerrado) tree species from central Brazil. Two stem tissues were studied, the active xylem or sapwood and the living tissues located between the cambium and the cork, made up predominantly of parenchyma cells (outer parenchyma). Outer parenchyma and sapwood density ranged from 320 to 410 kg m(-3) and from 420 to 620 kg m(-3), respectively, depending on the species. The denser sapwood tissues exhibited smaller relative changes in cross-sectional area per unit change in water potential compared with the outer parenchyma. Despite undergoing smaller relative changes in cross-sectional area, the sapwood released about 3.5 times as much stored water for a given change in area as the outer parenchyma. Cross-sectional area decreased earlier in the morning in the outer parenchyma than in the sapwood with lag times up to 30 min for most species. The relatively small lag time between dimensional changes of the two tissues suggested that they were hydraulically well connected. The initial morning increase in basal sap flow lagged about 10 to 130 min behind that of branch sap flow. Species-specific lag times between morning declines in branch and main stem cross-sectional area were a function of relative stem water storage capacity, which ranged from 16 to 31% of total diurnal water loss. Reliance on stored water to temporarily replace transpirational losses is one of the homeostatic mechanisms that constrain the magnitude of leaf water deficits in cerrado trees.     

Removal of nutrient limitations by long-term fertilization decreases nocturnal water loss in savanna trees

Under certain environmental conditions, nocturnal transpiration can be relatively high in temperate and tropical woody species. We have previously shown that nocturnal sap flow accounts for up to 28% of total daily transpiration in woody species growing in a nutrient-poor Brazilian Cerrado ecosystem. In the present study, we assessed the effect of increased nutrient supply on nocturnal transpiration in three dominant Cerrado tree species to explore the hypothesis that, in nutrient-poor systems, continued transpiration at night may enhance delivery of nutrients to root-absorbing surfaces. We compared nocturnal transpiration of trees growing in unfertilized plots and plots to which nitrogen (N) and phosphorus (P) had been added twice yearly from 1998 to 2005. Three independent indicators of nocturnal transpiration were evaluated: sap flow in terminal branches, stomatal conductance (g(s)), and disequilibrium in water potential between covered and exposed leaves (DeltaPsi(L)). In the unfertilized trees, about 25% of the total daily sap flow occurred at night. Nocturnal sap flow was consistently lower in the N- and P-fertilized trees, significantly so in trees in the N treatment. Similarly, nocturnal g(s) was consistently lower in fertilized trees than in unfertilized trees where it sometimes reached values of 150 mmol m(-2) s(-1) by the end of the dark period. Predawn gs and the percentage of nocturnal sap flow were linearly related. Nocturnal DeltaPsi(L) was significantly greater in the unfertilized trees than in N- and P-fertilized trees. The absolute magnitude of DeltaPsi(L) increased linearly with the percentage of nocturnal sap flow. These results are consistent with the idea that enhancing nutrient uptake by allowing additional transpiration to occur at night when evaporative demand is lower may avoid excessive dehydration associated with increased stomatal opening during the day when evaporative demand is high.