UV-C rays to simulate the exposition of photosynthetic organisms to solar radiation in space environments

Ultraviolet (UV) is a component of the solar radiation with a wavelength in the range of 100 ≤ λ ≤ 390 nm that is almost entirely shielded by the terrestrial atmosphere but not in space. The effects of UV-C (100 ≤ λ ≤ 280 nm) on plants mainly depend on a) the applied UV-C radiation dose and quality, b) the different plant species and varieties used, and c) the phenological phase of irradiated plants. UV-C radiation can be extremely dangerous also at low exposition times. On the other side, considering that terrestrial plants under sunlight are naturally exposed to low doses of UV-C, the question is how much UV-C could be beneficial for plants cultivated in space, in relation to a) protection of plants from pathogens, b) increase of the concentration of important dietary supplements, and c) regulation of some physiological processes. The research on UV-C should be more addressed to better evaluate the damages and benefits in UV-C-exposed photosynthetic organisms, involving plants useful for bioregenerative life support systems (BLSSs)

Identities in the spirit of Euler

In this paper we develop new identities in the spirit of Euler. We shall investigate and report on new Euler identities of weight p+2, for p an odd integer, but with a non unitary argument of the harmonic numbers. Some examples of these Euler identities will be given in terms of Riemann zeta values, Dirichlet values and other special functions.peerReviewe

Generalisation of a Waiting-Time Relation

AbstractA generalisation of a waiting-time relation is developed by the use of Laplace transform theory. The generalisation produces an infinite series and it is demonstrated how it may be summed by representation in closed form. Extensions and examples of the waiting-time relation are given

Some Boas-Bellman Type Inequalities in 2-Inner Product Spaces

Some inequalities in 2-inner product spaces generalizing Bessel's result that are similar to the Boas-Bellman inequality from inner product spaces, are given. Applications for determinantal integral inequalities are also provided

The effect of polyethylene glycol-induced oxidative stress on photosynthesis, carbohydrates and cell membrane in Stevia rebaudiana grown in greenhouse

Drought stress is one of the major environmental stresses that limit crop production in arid regions. A greenhouse culture experiment was conducted to evaluate the response of an agronomically and economically important sweet medical herb (Stevia rebaudiana) to polyethylene glycol (PEG 6000)-induced drought stress (5, 10, and 15% (w/v) PEG, equivalent to leaf water potentials of − 0.49, − 1.40 and − 2.93 MPa, respectively) for 1 month. Plant mass, a major determinant of Stevia yield, showed a reduction after PEG treatments. PEG-reduced photosynthesis traits included the maximal quantum yield of photosystem II (Fv/Fm), efficiency of photosystems I and II (PIabs), intercellular CO2, net photosynthesis, chlorophylls, carotenoids and water use efficiency, followed by the reduction of carbohydrates. Under PEG treatment, the reactive oxygen species (ROS) accumulation occurred and plants exhibited an increase in H2O2 generation. Consequently, an increase in malondialdehyde and electrolyte leakage was evident in PEG treatment, indicating membrane lipid peroxidation. In PEG-treated plants, the ROS accumulation was accompanied by an increase in activity of some enzymatic and non-enzymatic antioxidants. Leaf extracts of PEG-treated plants showed lower superoxide anion, hydroxyl and nitric oxide radical scavenging activity than control plants. Drought stress also caused the accumulation of the compatible solutes proline and glycine betaine. Collectively, the results demonstrated that PEG-induced oxidative stress, due to insufficient antioxidant mechanisms, provoked damages to cell membrane and photosynthetic apparatus, with consequently reduced carbohydrates and plant growth. These results are of basic importance as vegetative growth is the major determining criterion for Stevia crops and adequate irrigation is crucial for obtaining higher yield

Soil quality and fertility in sustainable agriculture, with a contribution to the biological classification of agricultural soils

Soils and crops are particularly vulnerable to climate change and environmental stresses. In many agrosystems, soil biodiversity and ecosystem services provided by soils are under threat from a range of natural and human drivers. Agricultural soils are often subject to agronomic practices that disrupt soil trophic networks and make soils less productive in the long term. In this scenario, sustainable soil use aimed at improving plant/root status, growth and development plays a crucial role for enhancing the biological capacity of agricultural soils. This commentary paper is divided into the following four main sections: (i) the contentious nature of soil organic matter; (ii) soil biological quality/fertility; (iii) soil classification; and, (iv) which agricultural practices can be defined as sustainable? The published literature was analyzed within a holistic framework, with agrosystems considered as living systems where soil, vegetation, fauna and microorganisms co-evolve and are reciprocally influenced. Ultimately, this article will suggest a better stewardship of agricultural soils as a natural capital

Structural and functional organization of the root system: a comparative study on five plant species

Plants are affected by soil environments to the same extent that they affect soil functioning through interactions between environmental and genetic factors. Here, five plant species (broad bean, pea, cabbage, fennel, and olive) grown under controlled pot conditions were tested for their ability to differently stimulate the degradation of standard litter. Litter, soil C and N contents were measured for evaluating chemical changes due to plant presence, while soil microbial abundance was evaluated to assess if it had a positive or negative catalyzing influence on litter decomposition. The architecture and morphological traits of roots systems were also evaluated by using specific open-source software (SmartRoot). Soil chemical and microbiological characteristics were significantly influenced by the plant species. Variations in soil C/N dynamics were correlated with the diversity of root traits among species. Early stage decomposition of the standard litter changed on the basis of the plant species. The results indicated that key soil processes are governed by interactions between plant roots, soil C and N, and the microbial metabolism that stimulate decomposition reactions. This, in turn, can have marked effects on soil chemical and microbiological fertility, both fundamental for sustaining crops, and can promote the development of new approaches for optimizing soil C and N cycling, managing nutrient transport, and sustaining and improving net primary production