Nowadays open field and protected vegetable cultivation practices require and use genotypes which are precisely tailored to their intended growth environments. Variability of this kind provides a rich source of material to uncover molecular mechanisms supporting the necessarily divergent physiological traits. In this study, typical field-optimized and glasshouse-cultivated cucumber F1 hybrids were investigated, and displayed slower growth (‘Joker’) and faster growth (‘Oitol’) in seedlings. Antioxidant capacity was lower in ‘Joker’ and higher in ‘Oitol’, pointing to a potential redox regulation of growth. The growth response of seedlings to paraquat treatment indicated stronger oxidative stress tolerance in the fast-growing ‘Oitol’. To test whether protection against nitrate-induced oxidative stress was also different, fertigation with increasing potassium nitrate content was applied. This treatment did not change growth but decreased the antioxidant capacities of both hybrids. Bioluminescence emission revealed stronger lipid peroxidation triggered by high nitrate fertigation in the leaves of ‘Joker’ seedlings. To explore the background of the more effective antioxidant protection of ‘Oitol’, levels of ascorbic acid (AsA), as well as transcriptional regulation of relevant genes of the Smirnoff–Wheeler biosynthetic pathway and ascorbate recycling, were investigated. Genes related to AsA biosynthesis were strongly upregulated at an elevated nitrate supply in ‘Oitol’ leaves only, but this was only reflected in a small increase in total AsA content. High nitrate provision also triggered expression of ascorbate–glutathion cycle genes with stronger or exclusive induction in ‘Oitol’. AsA/dehydro–ascorbate ratios were higher in ‘Oitol’ for all treatments, with a more pronounced difference at high nitrate levels. Despite strong transcriptional upregulation of ascorbate peroxidase genes (APX) in ‘Oitol’, APX activity only increased significantly in ‘Joker’. This suggests potential inhibition of APX enzyme activity specifically in ‘Oitol’ at a high nitrate supply. Our results uncover an unexpected variability in redox stress management in cucumbers, including nitrate inducibility of AsA biosynthetic and recycling pathways in certain genotypes. Possible connections between AsA biosynthesis, recycling and nitro-oxidative stress protection are discussed. Cucumber hybrids emerge as an excellent model system for studying the regulation of AsA metabolism and the roles of AsA in growth and stress tolerance.

Biophoton radiation also referred to as ultra-weak photon emission (UPE) is used to denote a spontaneous and permanent photon emission associated with oxidative processes in cells and seems to universally occur in all living systems as a result of the generation of reactive oxygen species (ROS) that are produced under stress conditions. The measurement of this biophoton emission allows for a non-invasive approach in monitoring phenological stages throughout plant development which has direct relevance in agriculture research. In this study, the emission of photons emanating from sunflower (Helianthus annuus, L.) plants exposed to biotic and abiotic stress has been investigated. In healthy plants raised under controlled growth conditions UPE was low whereas in stressed individuals it considerably increased; particularly upon water stress. The kinetics of the signal is shown to reveal an exponential decay with characteristic dynamics, which appears to reflect different physiological states concomitantly setting in upon stress. The dynamics of the signal decay is shown to vary according to the type of stress applied (biotic vs. abiotic) hence suggesting a putative relationship between the kinetic traits of change in the signal intensity-decay and stress. Intriguingly, the determination of the change in the intensity of biophoton emission that ensued in a short time course was possible by using the initial biophoton emission intensity. The predictability level of the equations demonstrated the applicability of the model in a corroborative manner when employing it in independent UPE-measurements, thus permitting to forecast the intensity change in a very accurate way over a short time course. Our findings allow the notion that albeit stress confers complex and complicated changes on oxidative metabolism in biological systems, the employment of biophoton imaging offers a feasible method making it possible to monitor oxidative processes triggered by stress in a non-invasive and label-free way which has versatile applications especially in precision agriculture.

Sunflower production plays an important role in global industrial oil production. Two-spotted spider mite, Tetranychus urticae, is a dangerous, polyphagous arthropod pest with a cosmopolitan distribution, which can endanger the economic features of global sunflower production. It is widely known that pests trigger various reactions in host plants. Among these, detection of ultra-weak photon emission (UPE) enhanced upon infestation is a novel, non-invasive method suitable for the visualisation and monitoring of both biotic and abiotic stress in living tissues. In the present study, the increase in ultra-weak UPE triggered by biotic stress caused by T. urticae in Helianthus annuus was measured. UPE response of injured plants differed from that of the control plants, which was reflected by a difference in bioluminescence intensity. In leaves attacked by T. urticae the onset value of average photon count detected by the sensor and expressed in cps (counts per second) was one order of magnitude higher on average as compared to that revealed by uninjured leaves. Furthermore, UPE emission in infested leaves resulted in an abrupt decrease in the ultra-weak photon emission intensity when assayed as a function of time. The use of this non-invasive imaging technique has allowed the detection of the injury induced by T. urticae, as a biotic stressor.

Silicon (Si) is a ubiquitous element in soil with well-known beneficial effects under certain conditions, in several plant species, if supplied in available form for uptake. It may alleviate damage in various stress situations and may also promote growth when no obvious stressors are applied. Effects of Si are often linked to mitigation of oxidative stress, in particular to the induction of antioxidant defense mechanisms. In the work presented, the impact of silicon provision on pro-oxidant systems was investigated in cucumber. Plants of the F1 cultivar hybrid ‘Joker’ were grown under in vitro conditions in the absence of any applied external stressor. Silicon provision decreased H₂O₂ content and lowered lipid peroxidation in the leaves of the treated plants. This was paralleled by declining polyamine oxidase (PAO) and diamine oxidase (DAO) activities. Several PAO as well as lipoxygenase (LOX) genes were coordinately downregulated in Si-treated plants. Unlike in similar systems studied earlier, the Si effect was not associated with an increased transcript level of gene coding for antioxidant enzymes. These results suggest an inhibitory effect of Si provision on pro-oxidant amine oxidases, which may decrease the level of reactive oxygen species by retarding their production. This extends the molecular mechanisms linked to silicon effects onto redox balance in plants.

During in vitro fertilization of wheat (Triticum aestivum, L.) in egg cells isolated at various developmental stages, changes in cytosolic free calcium ([Ca²⁺]_cyt) were observed. The dynamics of [Ca²⁺]_cyt elevation varied, reflecting the difference in the developmental stage of the eggs used. [Ca²⁺]_cyt oscillation was exclusively observed in fertile, mature egg cells fused with the sperm cell. To determine how [Ca²⁺]_cyt oscillation in mature egg cells is generated, egg cells were incubated in thapsigargin, which proved to be a specific inhibitor of the endoplasmic reticulum (ER) Ca²⁺-ATPase in wheat egg cells. In unfertilized egg cells, the addition of thapsigargin caused an abrupt transient increase in [Ca²⁺]_cyt in the absence of extracellular Ca²⁺, suggesting that an influx pathway for Ca²⁺ is activated by thapsigargin. The [Ca²⁺]_cyt oscillation seemed to require the filling of an intracellular calcium store for the onset of which, calcium influx through the plasma membrane appeared essential. This was demonstrated by omitting extracellular calcium from (or adding GdCl₃ to) the fusion medium, which prevented [Ca²⁺]_cyt oscillation in mature egg cells fused with the sperm. Combined, these data permit the hypothesis that the first sperm-induced transient increase in [Ca²⁺]_cyt depletes an intracellular Ca²⁺ store, triggering an increase in plasma membrane Ca²⁺ permeability, and this enhanced Ca²⁺ influx results in [Ca²⁺]_cyt oscillation.

Rodh Mulazai is a small town in Pishin District, Balochistan, Pakistan. This study investigated the soil quality of agricultural lands in this region. The 20 field sites were sampled. All these sites had orchards (commonly apple), and three of them had tree-based intercropping systems with wheat or tomato. These agricultural lands were 7–25 years old and were commonly under conservation agriculture since the beginning. The concentration of soil organic matter in the upper 0–10 cm depth of these field sites ranged from 9.33 to 41 g kg-1. A total of 13 soil macrofauna species were found, and the most common and abundant was the earthworm Lumbricus terrestris, followed by the earthworm Lumbricus rubellus. There was no relationship found between the total number of soil fauna and the concentration of soil organic matter at these field sites, nor did soil organic matter have a relationship with the concentration of soil clay contents. Likewise, the age of these sites with continuous conservation agriculture had no relation to the concentration of soil organic matter.