Cereals are a staple food in many regions of the world and are essential for global food security. Lead is one of the most significant environmental stressors, impacting plants throughout their life cycle and causing substantial damage to plant growth and development. It disrupts intracellular processes, thereby reducing plant productivity. The aim of this study was to determine the effect of exogenously applied vitamin PP (100 mu M) (nicotinamide) on the morphological, physiological, and biochemical parameters of spring barley var. Eunova under lead stress (1 mM Pb(NO3)2) and to determine the most effective method of applying this vitamin in a pot experiment. Vitamin PP was applied exogenously through three different methods: seed soaking, foliar application, and soil irrigation. The application of 1 mM Pb(NO3)2 resulted in decreased root (from 13.9% to 19.9%) and shoot length (from 16.2% to 24.8%) and increased catalase (CAT) activity from 45% to 106%, and peroxidase (POX) activity from 39% to 46% compared to the control. Lead stress led to an increase in proline (Pro) content from 30 to 63% and comparatively in malondialdehyde (MDA) content (rising from 61% to 79.4%), as well as elevated assimilatory pigment content (by 35%) in barley grown in the pot experiment. Exogenous vitamin PP significantly and positively influenced the improvement of the measured morphological, biochemical, and physiological parameters, reducing the toxicity of lead salts. It was shown that the most effective method of vitamin PP application was achieved through foliar spraying and irrigation.

Planting macadamia in karst rocky desertification areas has significant ecological and economic benefits. However, the production of macadamia in karst area are facing serious drought challenges due to the poor water holding capacity of soil, and less and uneven precipitation resulting with the rising of temperature in the world. Selecting and breeding drought-resistant rootstocks is one of the main measures to solve this problem in macadamia nut production in karst area. In this study, the morphological and physiological performance of half-sib family offspring of 14 macadamia cultivars were investigated under severe drought conditions and their drought resistance was evaluated comprehensively in order to select the most suitable macadamia rootstocks. Results revealed that the leaves of all rootstocks were damaged after drought stress. Among the tested rootstocks, the leaves of QA5 were damaged the most severely, and the leaves of the whole plants were chlorotic, followed by C11, A4, and NY2, while the symptoms in leaves of O.C and H2 was less obvious after drought stress for 30 d. At the same time, the O.C and H2 had the lowest drought injury index (DII), which was 0.40, while the QA5 had the highest DII value (0.82). The physiological indices, including malonaldehyde (MDA), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), soluble protein (SP), soluble sugar (SS), proline (Pro) and relative electrolyte leakage (REL) increased (Drought tolerance coefficient, DTC > 1) after drought stress, while relative water content of leaves (L-RWC), chlorophyll (Chl), relative water content of roots (R-RWC) and root activity (RA) decreased (DTC < 1) in all cultivars. Except SP, SS and Pro, there were significant differences in other indexes among different rootstocks. The 13 physiological indices were transformed into seven independent, comprehensive indices through principal component analysis (PCA), whose cumulative contribution ratio reached 82.905%. The 14 rootstocks were divided into 3 categories based on the comprehensive evaluation value (D). The O.C and H2 were clustered into the drought-tolerant group, whose D values were 0.743 and 0.669, respectively. The NY3, 333, 788, NY116, NY1, NY2 were belonged to the intermediate drought tolerance group, the D values were 0.530, 0.508, 0.497, 0.465, 0.457 and 0.441 respectively. Lastly, A16, A4, C11. GR1, 695 and QA5 were clustered into low drought tolerance group with the lowest D values of 0.396, 0.391, 0.360, 0.360, 0.355, 0.324, respectively. The result of stepwise regression analysis showed that MDA, POD, APX, SS, REL, R-RWC and RA were the most significant physiological and biochemical indices that played a significant role in drought tolerance, and could be used as the primary evaluation and identification indicators of drought tolerance of macadamia. These results indicated that the drought-resistant rootstocks of macadamia could improve their drought resistance by stimulating the cluster root development, increasing antioxidant enzyme activity and raising the content of osmotic regulatory substances under drought stress. Our study not only provided alternative rootstocks for macadamia drought-resistant cultivation, but also provided the theoretical basis for the drought-resistant rootstock breeding of macadamia by expounding the physiological mechanism of drought-resistance.

Heliotropium thermophilum (Boraginaceae) plants have strong antioxidant properties. This study investigated the effectiveness of the antioxidant system in protecting the photosynthetic machinery of H. thermophilum. Plants were obtained from K & imath;z & imath;ldere geothermal area in Buharkent district, Ayd & imath;n, Turkey. Plants in the geothermal area that grew at 25-35 degrees C were regarded as the low temperature group, while those that grew at 55-65 degrees C were regarded as the high temperature group. We analysed the physiological changes of these plants at the two temperature conditions at stage pre-flowering and flowering. We meaured the effect of high soil temperature on water potential, malondialdehyde, cell membrane stability, and hydrogen peroxide analysis to determine stress levels on leaves and roots. Changes in antioxidant enzyme activities, ascorbate and chlorophyll content, chlorophyll fluorescence, photosynthetic gas exchange parameters, and photosynthetic enzymes (Rubisco and invertase) activities were also determined. Our results showed minimal changes to stress levels, indicating that plants were tolerant to high soil temperatures. In general, an increase in antioxidant enzyme activities, ascorbat levels, and all chlorophyll fluorescence parameters except for non-photochemical quenching (NPQ) and F-v/F-m were observed. The pre-flowering and flowering stages were both characterised by decreased NPQ, despite F-v/F-m not changing. Additionally, there was a rise in the levels of photosynthetic gas exchange parameters, Rubisco, and invertase activities. High temperature did not affect photosynthetic yield because H. thermophilum was found to stimulate antioxidant capacity, which reduces oxidative damage and maintains its photosynthetic machinery in high temperature conditions and therefore, it is tolerant to high soil temperature.

The Loess Plateau, located in Gansu Province, is an important energy base in China because most of the oil and gas resources are distributed in Gansu Province. In the last 40 a, ecological environment in this region has been extremely destroyed due to the over-exploitation of crude-oil resources. Remediation of crude-oil contaminated soil in this area remains to be a challenging task. In this study, in order to elucidate the effects of organic compost and biochar on phytoremediation of crude-oil contaminated soil (20 g/kg) by Calendula officinalis L., we designed five treatments, i.e., natural attenuation (CK), planted C. officinalis only (P), planted C. officinalis with biochar amendment (PB), planted C. officinalis with organic compost amendment (PC), and planted C. officinalis with co-amendment of biochar and organic compost (PBC). After 152 d of cultivation, total petroleum hydrocarbons (TPH) removal rates of CK, P, PB, PC and PBC were 6.36%, 50.08%, 39.58%, 73.10% and 59.87%, respectively. Shoot and root dry weights of C. officinalis significantly increased by 172.31% and 80.96% under PC and 311.61% and 145.43% under PBC, respectively as compared with P (P<0.05). Total chlorophyll contents in leaves of C. officinalis under P, PC and PBC significantly increased by 77.36%, 125.50% and 79.80%, respectively (P<0.05) as compared with PB. Physical-chemical characteristics and enzymatic activity of soil in different treatments were also assessed. The highest total N, total P, available N, available P and SOM occurred in PC, followed by PBC (P<0.05). C. officinalis rhizospheric soil dehydrogenase (DHA) and polyphenol oxidase (PPO) activities in PB were lower than those of other treatments (P<0.05). The values of ACE (abundance-based coverage estimators) and Chao indices for rhizospheric bacteria were the highest under PC followed by PBC, P, PB and CK (P<0.05). However, the Shannon index for bacteria was the highest under PC and PBC, followed by P, PB and CK (P<0.05). In terms of soil microbial community composition, Proteiniphilum, Immundisolibacteraceae and Solimonadaceae were relatively more abundant under PC and PBC. Relative abundances of Pseudallescheria, Ochroconis, Fusarium, Sarocladium, Podospora, Apodus, Pyrenochaetopsis and Schizpthecium under PC and PBC were higher, while relative abundances of Gliomastix, Aspergillus and Alternaria were lower under PC and PBC. As per the nonmetric multidimensional scaling (NMDS) analysis, application of organic compost significantly promoted soil N and P contents, shoot length, root vitality, chlorophyll ratio, total chlorophyll, abundance and diversity of rhizospheric soil microbial community in C. officinalis. A high pH value and lower soil N and P contents induced by biochar, altered C. officinalis rhizospheric soil microbial community composition, which might have restrained its phytoremediation efficiency. The results suggest that organic compost-assisted C. officinalis phytoremediation for crude-oil contaminated soil was highly effective in the Loess Plateau, China.