EFFECT OF VERMICOMPOST DOSES ON CANABIS SATIVA PHOTOSYNTHESIS-RELATED PARAMETERS, GROWTH AND YIELD

Hemp, Cannabis sativa is certainly a mul­tifunctional as well as a niche crop, due to great po­ten­tial for innovative use of its different products. Aspects of hemp mineral nutrition are very important in the cultivation of these plants, in particular to make cul­ti­vation environmentally friendly by replacing synthetic fertilizers with organic ones. Among organic fertilizers, vermicompost has gained particular attention within the last decades. Explaining the role of vermicompost, this study evaluated the effects of different doses of this fer­ti­lizer on hemps in two separate field studies. In a small-scale field experiment, the effect of two doses of ver­micompost and adequate concentrations of mineral elements fertilizers the growth, physiological condition, as well as yield of hemp was compared. The effect of increasing doses of vermicompost on the physiological condition and yield of hemp was analysed in a broader field experiment. The experiments were performed at the Viļāni Scientific Centre of the Agricultural Resour­ces and Economics, in 2017 and 2018, using the Latvian hemp cultivar ‘Pūriņi’. For the experiments, certified vermicompost produced by ‘Eko Zeme’ (Latvia) was used, which was produced from composted cow manure by adding grass biomass. In field experiment, the posi­tive effect of vermicompost on hemp growth was greater than the effect of equivalent mineral fertilizer con­centra­tions. When using vermicompost in increasing doses, better hemp growth (40–60 %) was observed at 5 and 10 t ha-1, stem yield increased on average by 40 % due vermicompost, seed yield ranging from 1.00 t ha-1 in control plants, to 1.56 t ha-1 in 20 t ha-1 in plants treated with 20 t ha–1 vermicompost plants. The weight of 1000 seeds per plant in all variants (from 13.54 to 13.85 g) was relatively close to the indicated maximum level (14.59 g). A statistically significant increase in chlo­ro­phyll concentration in plant leaves was observed under the influence of vermicompost. The increase in the Per­for­mance Index of the chlorophyll a fluorescence measu­rement was only for plants in individual experimental variants; regardless of how significant the increase in stem and seed yield was due to the respective doses of vermicompost. In general, the results characterize the growth of hemp in local agroclimatic conditions and allow to expect a stable increase in yield under the in­fluence of vermicompost.

Investigation of European shot-hole borer, Xyleborus dispar (Coleoptera, Scolytidae), in apple orchards of Latvia

European shot-hole borer is known to occur on a wide range of deciduous trees and frequently found on fruit trees in most of the Holarctic. During the last years increased activity of this beetle contributed necessity for investigation of it in apple orchards of Latvia. Because of the latent behavior it is difficult to control distribution of Xyleborus dispar. Often insecticides are not effective, especially if not used in an appropriate time and methods of integrated or biological plant protection are needed. In the current study, results of two year monitoring of X. dispar flying activity and effectiveness of two types of sticky traps, Rebell Rosso and Csalomon Palx, bitted with 50% alcohol are presented. Four traps of each type were placed in each orchard at the beginning of May in 2013 and at the middle of April in 2014. Differences among respective orchards were recorded: the highest number of beetles was found in the largest orchard surrounded by wide deciduous forests; the lowest number was recorded in the orchard surrounded by the agricultural lands. The first emerging X. dispar female was caught at the middle of April. During the vegetation season the highest flying activity of beetles was at the end of April - beginning of May (17th – 18th week). Afterwards number and flying activity of beetles decreased and at the middle of June (25th – 26th week) reached zero. In orchard with the highest number of European shot-hole borer, significantly higher number of beetles was recorded on Rebell Rosso traps; for the rest two orchards higher number of X. dispar was recorded on Csalomon Palx traps

Disentangling the Belowground Web of Biotic Interactions in Temperate Coastal Grasslands: From Fundamental Knowledge to Novel Applications

Grasslands represent an essential part of terrestrial ecosystems. In particular, coastal grasslands are dominated by the influence of environmental factors resulting from sea–land interaction. Therefore, coastal grasslands are extremely heterogeneous both spatially and temporally. In this review, recent knowledge in the field of biotic interactions in coastal grassland soil is summarized. A detailed analysis of arbuscular mycorrhiza symbiosis, rhizobial symbiosis, plant–parasitic plant interactions, and plant–plant interactions is performed. The role of particular biotic interactions in the functioning of a coastal grassland ecosystem is characterized. Special emphasis is placed on future directions and development of practical applications for sustainable agriculture and environmental restoration. It is concluded that plant biotic interactions in soil are omnipresent and important constituents in different ecosystem services provided by coastal grasslands

Medium pH aff ects regeneration capacity and oxidative enzyme activity of Pinus sylvestris in tissue culture

Abstract Medium pH that is one of the important factors of the physico-chemical environment during development of plant tissues in conditions of in vitro culture which is modifi ed during preparation of media, but also changes with developing explants. Th e present experiments were performed to monitor the changes of medium pH and to determine the eff ect of medium pH on physiological characteristics of mature Pinus sylvestris L. tissue cultivated in vitro. Th e fi nal changes of medium pH aft er addition of agar and autoclaving were towards alkalinity in the range of initial pH 3.0 to 5.5. Results of the experiments proved that in general cultivation of pine buds causes acidifi cation of the medium. Th e degree of acidifi cation of medium during cultivation depends on initial pH of medium, morphogenesis of explants and duration of cultivation period without transplantation. Lowered activity of oxidative enzymes in buds cultivated on more acidic medium and less necessity for acidifi cation to reach the equilibrium in medium pH suggest that a low initial pH is more suitable for successful pine bud morphogenesis

Salinity Tolerance and Ion Accumulation of Coastal and Inland Accessions of Clonal Climbing Plant Species <i>Calystegia sepium</i> in Comparison with a Coastal-Specific Clonal Species <i>Calystegia soldanella</i>

Plant species adapted to saline habitats represent an important resource in the assessment of salinity tolerance mechanisms. The aim of the present study was to analyze salinity tolerance and ion accumulation characteristics for various accessions of Calystegia sepium from different habitats in comparison to these of Calystegia soldanella in controlled conditions. Plants were introduced in culture using stem explants with leaf and were cultivated in controlled conditions under six different substrate salinities. Salinity tolerance of both C. sepium and C. soldanella plants was relatively high, but the tolerance of particular accessions did not depend on the substrate salinity level in their natural habitats. C. sepium accession from a mesophytic non-saline habitat was only slightly negatively affected by increasing substrate salinity. However, coastal accession of C. sepium and coastal-specific species C. soldanella had some similarities in ion accumulation characteristics, both accumulating a high concentration of soluble ions in aboveground parts and excluding them from underground parts. All C. sepium accessions from different habitats represented varied physiotypes, possibly associated with their genetic differences. C. sepium accessions from different habitats can be suggested as models for further studies aiming at dissecting possible genetic, epigenetic and physiological mechanisms of adaptation to heterogeneous environmental conditions

<i>Ranunculus sceleratus</i> as a Model Species to Decrypt the Role of Ethylene in Plant Adaptation to Salinity

The aim of the present study was to develop an experimental system for an exploration of ethylene-dependent responses using intact growing Ranunculus sceleratus plants and to approbate the system for assessing the role of ethylene in salinity tolerance and ion accumulation. Plants were cultivated in sealed plastic containers in a modified gaseous atmosphere by introducing ethylene or 1-methylcyclopropene (1-MCP), a competitive inhibitor of ethylene action. High humidity inside the containers induced a fast elongation of the leaf petioles of R. sceleratus. The effect was ethylene-dependent, as 1-MCP completely blocked it, but exogenous ethylene further promoted petiole elongation. Exogenous ethylene decreased (by 48%) but 1-MCP increased (by 48%) the Na+ accumulation in leaf blades of NaCl-treated plants. The experimental system was further calibrated with ethylene and silica xerogel, and the optimum concentrations were found for inducing leaf petiole elongation (10 μL L–1 ethylene) and preventing leaf petiole elongation (200 g silica xerogel per 24 L), respectively. The second experiment involved a treatment with NaCl in the presence of 1-MCP, ethylene, or 1-MCP + ethylene, both in normal and high air humidity conditions. In high humidity conditions, NaCl inhibited petiole elongation by 25% and ethylene treatment fully reversed this inhibition and stimulated elongation by 12% in comparison to the response of the control plants. Treatment with 1-MCP fully prevented this ethylene effect. In normal humidity conditions, NaCl inhibited petiole elongation by 20%, which was reversed by ethylene without additional elongation stimulation. However, 1-MCP only partially inhibited the ethylene effect on petiole elongation. In high humidity conditions, ethylene inhibited Na+ accumulation in NaCl-treated plants by 14%, but 1-MCP reversed this effect. In conclusion, the stimulation of endogenous ethylene production in R. sceleratus plants at a high air humidity or in flooded conditions reverses the inhibitory effect of salinity on plant growth and concomitantly inhibits the accumulation of Na+ in tissues. R. sceleratus is a highly promising model species for use in studies regarding ethylene-dependent salinity responses and ion accumulation potential involving the manipulation of a gaseous environment

Vermicompost Amendment in Soil Affects Growth and Physiology of Zea mays Plants and Decreases Pb Accumulation in Tissues

Minimization of the possible harmful effects of soil pollution on agricultural production and food safety are the major challenges in modern agriculture. There is great scientific interest in the detailed understanding of the physiology of lead uptake and toxicity in Zea mays, together with the search for approaches to minimizing Pb accumulation in tissues. The aim of the present study was to explore the possibility of reducing Pb accumulation in Z. mays plants cultivated in Pb-contaminated soil, by means of vermicompost amendment. Z. mays plants were cultivated at three soil vermicompost amendment rates (10, 20, and 30%), with the addition of 1000 mg L&minus;1 of Pb in the form of Pb(NO3)2 or an equivalent amount of nitrogen in the form of NH4NO3. Additional nitrogen had a significant stimulatory effect on plant growth and physiology, but only for control plants, and at a low vermicompost amendment rate. Independently, Pb had an insignificant negative effect on plant growth and biomass partitioning, but significantly negatively affected the mineral nutrition of Z. mays plants. At a 10 and 20% soil vermicompost amendment rate, the Pb concentration in plant leaves and roots decreased by 65%, while plant biomass increased four to five times in comparison to soil-grown control plants, together with accelerated flowering. It was concluded that vermicompost is one of the most promising soil amendments for reducing heavy metal uptake and accumulation in crop plants, while also being an efficient organic fertilizer

Vermicompost Amendment in Soil Affects Growth and Physiology of <i>Zea mays</i> Plants and Decreases Pb Accumulation in Tissues

Minimization of the possible harmful effects of soil pollution on agricultural production and food safety are the major challenges in modern agriculture. There is great scientific interest in the detailed understanding of the physiology of lead uptake and toxicity in Zea mays, together with the search for approaches to minimizing Pb accumulation in tissues. The aim of the present study was to explore the possibility of reducing Pb accumulation in Z. mays plants cultivated in Pb-contaminated soil, by means of vermicompost amendment. Z. mays plants were cultivated at three soil vermicompost amendment rates (10, 20, and 30%), with the addition of 1000 mg L−1 of Pb in the form of Pb(NO3)2 or an equivalent amount of nitrogen in the form of NH4NO3. Additional nitrogen had a significant stimulatory effect on plant growth and physiology, but only for control plants, and at a low vermicompost amendment rate. Independently, Pb had an insignificant negative effect on plant growth and biomass partitioning, but significantly negatively affected the mineral nutrition of Z. mays plants. At a 10 and 20% soil vermicompost amendment rate, the Pb concentration in plant leaves and roots decreased by 65%, while plant biomass increased four to five times in comparison to soil-grown control plants, together with accelerated flowering. It was concluded that vermicompost is one of the most promising soil amendments for reducing heavy metal uptake and accumulation in crop plants, while also being an efficient organic fertilizer