Vol 65, No 6 (2018)

Literary data on very long-chain fatty acids (VLCFAs) that are present in polar lipids of the plant cell membranes are discussed. Large amounts of VLCFA are found in polar lipids of some cellular organelles as well as in nonextractable lipids from diverse plant objects, where the influence of surface lipids on the relative content of these FAs is excluded. In some plants, the VLCFA fraction in membrane lipids increases under several kinds of stress. Amounts and diversity of VLCFAs are lower in flowering plants as compared with the representatives of more ancient taxons—gymnosperms, ferns, and marine algae. Presence of VLCFAs in the composition of annular lipids of the cell membranes is assumed. Biosynthesis of VLCFAs, enzymes involved in the process, and encoding genes are discussed.

Potato Solanum phureja Juz. & Bukasov crop species' metobolome at the flowering stage includes 234 compounds, 117 of which were identified. The most represented group among them contains sugars and their derivatives that are in accordance with intensive carbohydrate exchange of potato tissues and organs. Young leaves and developing reproductive organs are characterized by a wide spectrum of organic and amino acids, nitrogen-containing compounds, and lipids as well as compounds of secondary metabolism that may indicate the intensity of metabolic processes and the formation of defense mechanisms. Depletion of metabolites’ profile in senescent leaves agrees with the idea of weakening synthetic processes in them and the onset of metabolites’ outflow to new forming attracting potato organs. Specificity of metabolic profiles, which corresponds to age and physiological status of potato organ or tissue, was revealed.

Allelopathy is very important for the scientific disposition of garden plants. To understand the allelopathic potential of Koelreuteria bipinnata Franch. var. integrifoliola, the germination of Agrostis tenuis Sibth., Festuca arundinacea Schreb. and Lolium perenne L. were determined under laboratory conditions. The results showed that root, stem and leaf aqueous extracts of K. bipinnata var. integrifoliola had allelopathic effects on all three turf grasses, and the allelopathic activity varied according to extract concentrations, test species, and extract sources. Lower extract concentrations did not affect or promoted the germination and initial seedling growth of turf grasses, but the highest concentrations almost had inhibitory effect. The order of allelopathic potentials of the three organs on germination of these receptors was root < stem < leaf. And at the highest concentration of leaf extract, the most strongly inhibition was found in A. tenuis, followed by F. arundinaces and then L. perenne. In addition, according to gas chromatography–mass spectrometry (GC–MS) analysis, the allelopathic potential compounds and their abundance in root, stem and leaf were obviously different. Therefore, the allelopathic compounds may responsible for allelopathy of K. bipinnata var. integrifoliola. These findings suggested that more attention should be paid to the leaf of K. bipinnata var. integrifoliola for the relative higher allelopathic effects.

To clarify how the components of the entire photosynthetic electron transport chain in response to drought stress in maize. The activities of photosystem II (PSII), photosystem I (PSI), and the electron transport chain between PSII and PSI of maize were investigated by prompt fluorescence (PF), delayed fluorescence (DF) and 820 nm modulated reflection (MR). Maize (Zea mays L.) plants were subjected to different levels of soil water availability including control, moderate and severe drought stress. A significant decrease in ϕE₀, Ψ₀ and PI_ABS was found in maize treated with moderate drought stress. A significant increase in ABS/RC was observed, but there were no significant change in the fast MR phase and the amplitude of DF under moderate drought stress compared to the control. Under severe drought stress, the exchange capacity between Q_A to Q_B, reoxidation capacity of plastoquinol, and the oxidation and re-reduction rates of PC and P₇₀₀ all decreased. These results demonstrated that moderate drought stress reduced the photochemical activity of PSII from Q_A to PQH₂, while the photochemical activity of PSI was unscathed. However, severe drought stress inhibited the entire electron transport chain from the donor side of PSII to PSI-end electron acceptors. In addition, the photochemical activity of PSII is more sensitive to drought stress than PSI.

Growing evidence indicates that calcium-dependent protein kinases (CDPKs) are involved in many aspects of plant’s growth, development and responses to biotic and abiotic stresses. Previous researchers reported AtCDPK1 gene used as a positive regulator in salt and drought stress signaling. This study aimed to increase transgenic potatoes’ (Solanum tuberosum L. cv. Favorita) tolerance to the drought and osmotic stresses. Transgenic potato plants expressing AtCDPK1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter (referred to as T-plants) were successfully generated through Agrobacterium-mediated transformation. Two representative transgenic T6 and T25 lines were evaluated for enhanced tolerance to drought and osmotic stresses. The survival rates of transgenic lines T6 and T25 (67 and 54%, respectively) were higher than that of wild type (WT) plants (25%) after the drought stress. After 15 days of PEG stress, the survival rate of T6 was 45.68%, whereas that of the WT line was approximately 20%. The survival rate of transgenic lines was very higher than that of WT after 15 days of PEG stress. The content of proline and malondialdehyde (MDA) were clear difference between control and transgenic lines after the drought and osmotic stresses. After the 24 h osmotic treatment, content of proline in transgenic plants was very higher than that of the control, enhanced 26%, reached an extremely significant level (P < 0.05). MDA content in transgenic plants was lower than the control in the same period, while the biggest difference appeared at 24 h (P < 0.05), and MDA content of transgenic plants reduced 28% than the control. qRT-PCR proves that relative expressions of StP5CS and StProDH genes in the transgenic lines both increased in early period, and then decreased after PEG 6000 stress. These results suggested that enhanced AtCDPK1 expression affected the transcription of stress-associated genes and the content of proline and MDA in transgenic plants, which leads to improved tolerance ability in transgenic potatoes.

Physiological mechanisms of canola (Brassica napus L., cv. Westar) plant protection afforded by melatonin (at 0.1–100 μM) from copper salts (at 10–100 μM) were studied. Plants were cultivated on Hoagland–Snyder medium. At the age of 5 weeks, they were subjected to melatonin, copper sulfate, or their combination for 7 days. It was found that excessive copper in a nutrient medium inhibited the dry biomass accumulation against the control by 25–85%. Copper sulfate diminished the content of chlorophylls and carotenoids and functional activity of the thylakoid membranes in the chloroplasts. It increased 2.0–2.5 times the lipid peroxidation (LPO) intensity and the proline level up to 20 times. Melatonin reduced the changes caused by copper, and the degree of the protection depended on melatonin and CuSO₄ concentrations. It was found that melatonin decreased the oxidative stress and proline accumulation, both induced by CuSO₄. At first, we established the positive correlation (with the coefficient 0.8240) between the level of oxidative stress and proline content in the presence of CuSO₄. Possible mechanisms of protection by melatonin and its biological role under conditions of technogenic stress are discussed.

More than 20% of irrigated land has been influenced by salt stress, decreasing crop production. In this research, we investigated the effect of different levels of salinity (0, 50, 100 and 150 mM NaCl) and the efficiency of Piriformospora indica on growth, biochemical traits, antioxidative defense system in tomato (Solanum lycopersicum L.). NaCl stress reduced chlorophyll content, height and biomass of plants. Higher level of salinity (150 mM) declined the plant height by 22.65%, total dry weight by 56.44% and total chlorophyll by 44.34%, however, P. indica inoculation raised plant height by 43.47%, dry weight by 69.23% and total chlorophyll content by 48.09%. Salinity stress increased H₂O₂, malondialdehyde (MDA), superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) level in leaves and roots tomato seedlings. However, P. indica inoculation reduced H₂O₂, MDA and superoxide anion and enhanced DPPH compared to non-inoculated plants at all NaCl levels. The total phenol and flavonoids increased with NaCl treatment. On the other hand, the total phenolic and flavonoid increased more in P. indica inoculated plants compared to non-inoculated ones. Moreover, inoculation of P. indica implicated noteworthy improvement of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) activity in tomato upon salinity. Notably, colonization with P. indica significantly improved the content of reduced ascorbic acid (AsA), glutathione (GSH) and redox ratio in the tomato plants under salinity resulting in reduced redox state. Our findings confirmed that salinity had negative effect on tomato seedling; however, P. indica inoculation increased tolerance to salinity by improving the content of phenolic compounds, non-enzymatic antioxidants, and increasing the activity of antioxidant enzymes.

Trypophloeus klimeschi Eggers was first discovered in Xinjiang Province and had strong selection specificity for Populus alba var. pyramidalis Bunge. There was an outbreak of this beetle in the northwest shelter forest of China, resulting in significant economic losses and loss of ecological benefits. Based on a prior long-term field investigation, T. klimeschi had a different extent of injuries for different ages of P. alba var. pyramidalis and other Populus in the same area were not selected by T. klimeschi. To further explore the specificity volatile compounds, this study involved selecting host and non-host trees to analyse the volatile chemical profile of host and non-host poplars of T. klimeschi. The main volatile compounds of the host poplar P. alba var. pyramidalis for different physiological statuses and those of three other non-host poplars (P. alba L., P. tomentosa Carr., and P. dakuanensis Hsu) were analysed through solid-phase micro extraction (SPME) coupled with thermal desorption and gas chromatography-mass spectrometry (GC-MS). The major compound groups were aldehydes, esters, alcohols, ketones, phenols, terpenes and alkanes. Comparative analysis of the changes in the different physiological stages of P. alba var. pyramidalis and other non-host Populus volatile substances was conducted, and the results showed that 2-hydroxy-benzaldehyde, nonanal, decanal, 2-methyl-butanal, (Z)-3-hexen-1-ol benzoate, methyl benzoate, methyl salicylate, geraniol and salicyl alcohol might act as attractants for T. klimeschi, and 2-hexenal, hexanal, 2-cyclohexen-1-one, caryophyllene, eugenol, benzyl alcohol, and eucalyptol could be deterrents for T. klimeschi. These experiments may lead to the optimisation of a synthetic lure that may be used to detect and monitor T. klimeschi.