Drop impact dynamics on the hydrophobic leaf surface of an aquatic plant: a case study of Pistia stratiotes.

Pistia stratiotes is an aquatic plant with a complex structure that allows it to stay afloat. It grows quickly, and in large numbers becomes an undesirable plant as an invasive species. Describing the dynamics of a water drop splash on P. stratiotes leaves can contribute to increasing knowledge of its behavior and finding alternative methods for eradicating it or using it for the benefit of the environment. The non-wettable surface of P. stratiotes presents a complex structure-simple uniseriate trichomes and also ridges and veins. We analyzed the drop impact on a leaf placed on the water surface and recorded it by high-speed cameras. Based on the recordings, quantitative and qualitative analyses were performed. After impacting the leaf, the water drop spread until it reached its maximum surface area accompanied by the ejection of early droplets in the initial stage. Thereafter, three scenarios of water behavior were observed: (i) drop receding and stabilization; (ii) drop receding and ejection of late droplets formed in the later stage as an effect of elastic deformation of the leaf; and (iii) drop breaking apart and ejection of late droplets. The results indicated that the increasing kinetic energy of the impacting drops expressed by the Weber number and the complex leaf surface have an effect on the course of the splash. The simple uniseriate trichomes of the P. stratiotes leaf and the high energy of the falling drops were responsible for the formation and characteristics of the early droplets. The presence of ridges and veins and the leaf's mechanical response had an impact on the occurrence of late droplets.

Diffuse Reflectance Spectroscopy for Black Carbon Screening of Agricultural Soils under Industrial Anthropopressure.

Visible and near-infrared spectroscopy (VIS-NIRS) is a fast and simple method increasingly used in soil science. This study aimed to investigate VIS-NIRS applicability to predict soil black carbon (BC) content and the method's suitability for rapid BC-level screening. Forty-three soil samples were collected in an agricultural area remaining under strong industrial impact. Soil texture, pH, total nitrogen (Ntot) and total carbon (Ctot), soil organic carbon (SOC), soil organic matter (SOM), and BC were analyzed. Samples were divided into three classes according to BC content (low, medium, and high BC content) and scanned in the 350-2500 nm range. A support vector machine (SVM) was used to develop prediction models of soil properties. Partial least-square with SVM (PLS-SVM) was used to classify samples for screening purposes. Prediction models of soil properties were at best satisfactory (Ntot: R2 = 0.76, RMSECV = 0.59 g kg-1, RPIQ = 0.65), due to large kurtosis and data skewness. The RMSECV were large (16.86 g kg-1 for SOC), presumably due to the limited number of samples available and the wide data spread. Given our results, the VIS-NIRS method seems efficient for classifying soil samples from an industrialized area according to BC content level (training accuracy of 77% and validation accuracy of 81%).

Proteolytic and Structural Changes in Rye and Triticale Roots under Aluminum Stress.

Proteolysis and structural adjustments are significant for defense against heavy metals. The purpose of this study was to evaluate whether the Al3+ stress alters protease activity and the anatomy of cereale roots. Azocaseinolytic and gelatinolytic measurements, transcript-level analysis of phytocystatins, and observations under microscopes were performed on the roots of Al3+-tolerant rye and tolerant and sensitive triticales exposed to Al3+. In rye and triticales, the azocaseinolytic activity was higher in treated roots. The gelatinolytic activity in the roots of rye was enhanced between 12 and 24 h in treated roots, and decreased at 48 h. The gelatinolytic activity in treated roots of tolerant triticale was the highest at 24 h and the lowest at 12 h, whereas in treated roots of sensitive triticale it was lowest at 12 h but was enhanced at 24 and 48 h. These changes were accompanied by increased transcript levels of phytocystatins in rye and triticale-treated roots. Light microscope analysis of rye roots revealed disintegration of rhizodermis in treated roots at 48 h and indicated the involvement of root border cells in rye defense against Al3+. The ultrastructural analysis showed vacuoles containing electron-dense precipitates. We postulate that proteolytic-antiproteolytic balance and structural acclimation reinforce the fine-tuning to Al3+.

The Leaf Wettability of Various Potato Cultivars.

Leaf wettability has an impact on a plant's ability to retain water on its leaf surface, which in turn has many environmental consequences. In the case of the potato leaf (Solanum tuberosum L.), water on the leaf surface may contribute to the development of a fungal disease. If fungal disease is caused, this may reduce the size of potato harvests, which contribute significantly to meeting global food demand. The aim of this study was to assess the leaf wettability of five potato cultivars (i.e., Bryza, Lady Claire, Rudawa, Russet Burbank, Sweet Caroline) in the context of its direct and indirect impact on potato yield. Leaf wettability was assessed on the basis of contact angle measurements using a sessile drop method with an optical goniometer. For Bryza and Rudawa cultivars, which showed, respectively, the highest and the lowest contact angle values, light microscopy as well as scanning electron microscopy analyses were performed. The results of the contact angle measurements and microscopic image analyses of the potato leaf surfaces indicated that the level of wettability was closely related to the type of trichomes on the leaf and their density. Therefore, higher resistance of the Rudawa cultivar to biotic stress conditions could be the result of the presence of two glandular trichome types (VI and VII), which produce and secrete metabolites containing various sticky and/or toxic chemicals that may poison or repel herbivores.