Risk assessment for volunteer and seedling GM potatoes in the northernmost European growing areas

Abstract

Commercial production of genetically modified (GM) potatoes (Solanum tuberosum L.) could represent a risk to conventional production if volunteer plants develop from tubers or true seeds that survive until the following growing season. We studied such risks under northernmost European conditions and monitored the effects of cultivar, tuber size and tuber depth in the soil on winter survival at MTT Agrifood Research Finland, Jokioinen (61°06′N, 23°02′E) from 2004–2007. Tubers of two non-GM cultivars, Saturna and Asterix, and two size classes, 25–30 mm and 45–50 mm, were planted at depths of 10 and 20 cm in autumn, soon after harvest. In winters 2004–2005 and 2005–2006 all tubers planted in the soil in autumn were killed by frost. In 2005–2006, the field was covered by up to 30–40 cm of snow and the minimum soil temperatures ranged between ?0.4^oC and ?0.9^oC, but only 0.0–3.5% of the tubers survived and there was no difference between cultivars, tuber sizes and planting depths. Under laboratory conditions compared with ?2.0°C and ?2.5°C, treatment at ?3.0°C for 72 h resulted in significantly lower survival rate of the tubers (8.2%). Asterix, a late maturing table potato cultivar, was more resistant to low temperatures than the processing cultivar Saturna. In general, volunteer tubers are not currently a significant risk for coexistence of GM and conventional potato production in northern Europe due to the cold winter conditions but also due to possibilities to control the sporadic volunteers from the next crop. However, we noted that seedlings initiated from true potato seed are able to produce tubers despite the short growing season. Such a risk could be reduced by accepting only non-berry-producing GM cultivars for cultivation.     

Effects of nano-fertilizers on physiological and yield characteristics of pinto bean cultivars under water deficit stress

Abstract

In order to evaluate the effects of water deficit stress and foliar application of zinc (Zn) and iron (Fe) nanoparticles on physiological characters and seed yield of pinto bean, an experiment was designed as a split factorial design based on randomized complete blocks with three replications in two growing seasons (2016–2017 and 2017–2018). Treatments were included water deficit stress (normal irrigation and water deficit stress in 50% flowering), foliar application of nano-fertilizers (control, nano-Zn (1.5?g L^?1), nano-Fe (2?g L^?1) and combination of nano-Zn and nano-Fe) and four cultivars of pinto bean (Sadri, Coosha, Cos16, and Ghaffar). The results showed that the soluble sugars and proline content was increased under water deficit. Water deficit stress through decreasing chlorophyll and relative water content of leaves as well as the iron and zinc content of seeds, decreased seed yield and quality. The application of nano-fertilizers of zinc and iron enhanced antioxidant enzymes activity, proline and soluble sugars content as well as leaf area. Also applied nano-fertilizers improved seed quality in terms of protein content. According to obtained results the effect of foliar spray of nano-fertilizers on iron and zinc content of seeds regards to bean cultivars was different. It was concluded that the foliar application of iron combined zinc nano-fertilizers can be useful in pinto bean cultivars under water deficit stress. In both normal and water deficit Cos16 cultivar showed the better amount of studied characteristics compared to other cultivars. The results of cluster analysis of these cultivars confirmed the superiority of Cos16 cultivar.     

Influence of Potassium Rates and Sources on Seed Cotton Yield and Yield Components of Some Elite Cotton Cultivars

Abstract

A field experiment was conducted at Central Cotton Research Institute, Multan, Pakistan on Miani soil series, silt loam soil (Calcaric, Cambisols and fine silty, mixed Hyperthermic Fluventic Haplocambids) to assess the response of four cotton (Gossypium hirsutum L.) cultivars to potassium (K) fertilization. The treatments consisted of four cotton cultivars (CIM-448, CIM-1100, NIAB-Karishma, S-12), four potassium rates (0, 62.5, 125, 250 kg K ha^?1), and two sources of potassium fertilizer [muriate of potash (KCl) and sulphate of potash (K₂SO₄)]. The cotton cultivars differed significantly in response to various potassium fertilizer levels and its sources with respect to seed cotton yield and its components. The highest yield was obtained with the application of 250-kg K ha^?1, however, it was economical to add 125 kg K ha^?1. Seed cotton yield of cv. CIM-448 was considerably greater than that of the other cultivars in K-unfertilized treatments, which was related to cultivar differences in K uptake efficiency in utilizing native potassium nutrient. Potassium added as muriate of potash caused a significant depression in seed cotton yield than that of sulphate of potash. The increase in yield seemed to have resulted largely from the higher K concentration of leaf tissues at bloom stage and available soil-K because of potassium application. A significant relationship between the yield and number of bolls per plant (r = 0.92**) and boll weight (r = 0.85**) indicated that these two growth attributes were responsible for enhancing the quantum of final harvest of seed cotton.     

Response of Cotton and Wheat Cultivars to Soil-applied Boron in a Boron-deficient,Noncalcareous Typic Ustochrept

Field experiments were conducted to study the response of cotton genotypes (G. arboreum Bt cv. RCH 650 BGII; non-Bt cv. F 2228; G. herbaceum cv. FDK 124) and wheat and triticale genotypes (T. aestivum cv. PBW 622; T. durum cv. PDW 314; triticale cv. TL 2908) to direct and residual B application (0, 0.5, 1.0, and 2.0 kg B ha^?1 as borax) using a Typic Ustrochrept, neutral, noncalcareous, loamy sand and B-deficient soil. A significant response of 218 and 231 kg ha^?1 in seed cotton yield was recorded with an application of 1.0 kg B ha^?1 to cotton and 2.0 kg B ha^?1 to wheat. A significant response of 152 kg ha^?1 grain yield of wheat was observed with the application of 0.5 kg B ha^?1 to wheat, while no residual effect of B was observed when B was applied to cotton. On the basis of agronomic and B uptake efficiency, genotypes of cotton (RCH 650 BG II > FDK 124 > F 2228) and wheat (PDW 314> TL 2908> PBW 621) responded differentially to B application, thus indicating that yield of Bt cotton and durum wheat will be reduced more than the other cultivars under B deficiency.     

Use of Sieved Compost Plus Hydrogel for Solid Matrix Priming of Carrot Seeds

In this study we report the water release curve of a compost-based carrier for solid matrix priming and its effects on carrot seed germination. ‘Danvers Half Long’ and ‘Nantes Scarlet’ carrot (Daucus carota) seeds were primed for 7 d at 15°C in a carrier consisting of 5:1:5.7 sieved compost: hydrogel:distilled water (based on weight) equaling a water potential of ?1.0 MPa. Seeds were blended with carrier at 1:10, 1:20, 1:30, or 1:40 (based on weight) and compost priming was compared with a polyethylene glycol (PEG) priming procedure. Germination testing at 20-30°C (16-8 h) in darkness indicated that all compost priming treatments hastened seed germination more than PEG priming. Compost priming at 1:30 increased final germination percentage (FGP) for ‘Nantes Scarlet’ (FGP = 85%) compared to PEG primed (FGP = 72%) seeds but ‘Danvers Half Long’ FGP was similar for all treatments. For both cultivars, seeds that were compost primed had reduced G (days to 10% FGP) and G (days to 50% FGP) compared to PEG primed or nonprimed seed. For ‘Danvers Half Long’ carrot seeds, priming ratios of 1:30 reduced G values more effectively than all other treatments. For ‘Nantes Scarlet’ carrot seeds, G₁₀ and G₅₀ values were reduced similarly at all seed-to-carrier ratios. Compost primed seeds could be dried and stored for 35 d at 3 or 20-30°C (16-8 h) for ‘Danvers Half Long’ and for 35 d at 3°C for ‘Nantes Scarlet’ with no loss in priming benefit. We conclude that solid matrix priming with a compost based carrier is a satisfactory alternative to PEG priming to improve germination of carrot seed.     

Response of Chamecytisus palmensis to drought stress induced by polyethylene glycol during germination

Abstract

Seed germination and subsequent changes in Chamecytisus palmensis were studied under water limiting conditions, imposed by increasing concentrations of polyethylene glycol (PEG-6000) (0, 5, 10, 15, 20, 25, and 30%). Six water stress conditions (C. palmensis. Seed germination was completely inhibited under the drought stress of 30% (?1.20?MPa). Similar to the seed germination, the growth of radicles and hypocotyls after seed germination was also restricted by PEG-simulated drought stress, especially when water potential was lower than ?0.12?MPa (25%). In the same way, the ratio of radicles and hypocotyls significantly decreased with the increase of PEG concentrations, demonstrating strong adaptability to drought stress. Moreover, the decline of radicles and hypocotyls lead to a decrease in the number of root hairs. This would seriously affect the water absorption ability of the young roots. It was concluded that drought stress might be one of the causes for obstructed natural regeneration of C. palmensis plantations on sandy land.     

ROOT ZONE TEMPERATURE INFLUENCES ZINC REQUIREMENT OF MAIZE CULTIVARS ON A CALCAREOUS LOAM SOIL

The zinc (Zn) requirement of a maize (Zea mays L.) hybrid (‘FHY-396’) and an indigenous variety (‘EV-7004’) was measured at low (22.4 ± 5°C) and high (28.8 ± 5°C) root-zone temperatures (RZT). Four Zn rates (0, 3, 9 and 27 mg kg^?1 soil) were applied to a calcareous loam soil in pots for the glasshouse study. Shoot and root dry matter yields were significantly more at the higher RZT. Regardless the RZT, maximum relative shoot dry matter yield in hybrid and variety was produced, respectively, at 9 and 3 mg Zn kg^?1 soil. Zinc concentration in roots and shoots of both the cultivars increased with Zn rates and it was significantly more at the higher RZT. Cultivars differed in critical Zn concentration (C_ZnC) required for maximum shoot dry matter yield. The C_ZnC ranged from 25 to 39 μg Zn g^?1 plant tissue for optimum growth of both the cultivars at low and high RZT.     

K-priming positively modulates growth and nutrient status of salt-stressed cotton (Gossypium hirsutum) seedlings

Being macronutrient, K⁺ is involved in a number of metabolic processes including stimulation of over 60 enzymes. The present study was conducted to investigate whether K-priming could alleviate the effects of salinity on the growth and nutrient status of cotton seedlings. The seeds of two cotton cultivars, namely FH-113 and FH-87, were primed with solutions of three potassium sources (KNO₃, K₂SO₄ and K₂HPO₄) using three concentrations (0%, 1.25% and 1.5%) of each potassium source. After 1 week of germination, the seedlings were subjected to salinity (0 and 200 mM NaCl) stress. The results showed that salinity significantly affected growth and nutrients status of cotton seedlings. The K-priming alleviated the stress condition and significantly improved dry matter as well as nutrient uptake in cotton seedlings. Of the priming treatments pre-sowing treatment with KNO₃ (1.5%) was most effective in increasing shoot and root lengths and biomass of cotton seedlings. The seedlings raised from seed treated with KNO₃ (1.5%) showed varied accumulation of cations (Ca²⁺, Na⁺ and K⁺) and faced less oxidative stress irrespective of cotton cultivars under salt stress. The results suggested that pre-sowing seed treatment with KNO₃ (1.5%) might be recommended for synchronized germination and sustainable production of cotton crop under saline environments.     

The difference in the formation of thermotolerance of two cotton cultivars with different heat tolerance

ABSTRACT

In order to study the mechanism of thermotolerance of cotton cultivars with different heat tolerance, the response of yield component and photosynthesis to short-term heat stress (HT; average temperature 34°C) was studied. Pot experiments were carried out in 2015 and 2016 by using cotton cultivar PHY370WR (heat tolerant cultivar) and Sumian15 (heat susceptible cultivar). Results showed that heat (34°C) treatment resulted in a significant (p < 0.05) reduction in cotton yield. Path analysis showed that the direct path coefficient (0.89) of boll weight was higher, compared with the boll number (0.46). With high-temperature stress, it was the difference of boll weight reduction contributed the majority to the difference of yield reduction between cultivars, not the difference of boll number reduction. Different decrease in photosynthesis between cultivars leads to the different decline in boll weight. Different thermotolerance between the two cultivars were as follows: the heat tolerant cultivar could maintain higher photosynthesis rate under HT, and it could recover more quickly and highly in photosynthesis than the heat susceptible cultivar. More importantly, the leaf functional period of heat tolerant cultivar was less shortened by HT than that of heat susceptible cultivar.     

Water deficit and abscisic acid production of Salicornia bigelovii under salinity stress

We investigated the mechanism of growth reduction of dicotyledonous halophyte Salicornia bigelovii under salinity stress by growing it at 0.005 to 500?mol?m^?3 sodium chloride (NaCl). The optimal range for growth of S. bigelovii was between 50 and 200?mol?m^?3 NaCl. A significant correlation was found between growth and water content, which indicated that water deficit was an important factor in growth reduction at both suboptimal and supraoptimal salinities. Abscisic acid (ABA) concentration of the shoot was negatively related to growth and water content, which suggested that ABA induced by water deficit may inhibit growth at both the suboptimal and supraoptimal salinities. The cause of water deficit at supraoptimal salinity might be caused by nutritional imbalance and osmotic stress due to the low osmotic potential of the external solution. However, limited salt uptake may be one of the causes of water deficit under suboptimal salinity. We discuss a sodium ion (Na⁺) specific deficit rather than salt deficit as another possible cause of water deficit.     

Yield and water use efficiency of hybrid Bt cotton as affected by methods of sowing and rates of nitrogen under surface drip irrigation

Field experiments were conducted for two years to find out the appropriate sowing configuration and rate of nitrogen (N) for sustained yield and improved water use efficiency of hybrid Bt cotton irrigated through surface drip irrigation. Drip irrigation under normal sowing, in which equal quantities of water and N were applied as check-basin irrigation, resulted in an increase of 389 and 155 kg ha^?1 in seed cotton yield compared with check-basin irrigation during the first and second year, respectively. Normal paired row sowing under a drip irrigation system, in which only 50% of irrigation water was applied compared with normal sowing, produced a yield similar to normal sowing under drip irrigation during both years, resulting in 22% higher water use efficiency. Dense paired row sowing under drip irrigation, in which only 75% irrigation water was applied compared with normal sowing, increased the mean seed cotton yield by 5% and water use efficiency by 19%. Decrease in the rate of nitrogen application (from 150 to 75 kg N ha^?1) caused a decline in seed cotton yield and water use efficiency under all the methods of sowing, but the reverse was true for agronomic efficiency of N.     

棉花调亏灌溉的生理响应及其优化农艺技术

在移动式防雨棚下，采用盆栽土培法和测坑微区试验相结合的方法，分析了调亏灌溉对棉花不同生育阶段蒸腾速率（Tr）、光合速率（Pn）、光合产物积累与分配、经济产量（Y）和水分利用效率（WUE）的影响，盆栽试验采用二因素（水分调亏阶段和调节亏水度）随机区组设计，测坑微区试验采用三因素（水分调亏度、施肥水平和植株密度）正交旋转组合设计。结果表明：适时适度的水分调亏使得Tr明显下降，而Pn下降不明显，复水后光合产物具有超补偿积累，且有利于向经济产品（籽棉）运转与分配。棉花调亏灌溉（RDI）的适宜指标是：苗期轻、中度调亏，0～40cm土层湿度下限为50％FC～60％FC（田间持水量）；蕾期轻度调亏，0～40cm土层湿度控制下限为60％FC；花铃期不宜调亏，0～40cm土层湿度应不低于75％FC；吐絮期可中度调亏，0～40cm土层湿度可控制在50％FC～55％FC。     

Biopriming in bean seeds

The incorporation of biological control organisms in seeds may help control pathogens and improve seedling performance. The aim of this study was to determine the effects of biopriming bean seeds with Trichoderma spp. and Bacillus subtilis using physiological conditioning, suspensions of biological structures and film coating techniques. Biopriming treatments with suspensions of biological structures were performed using the commercial products Agrotrich plus^® and Rhizoliptus^®. Water restriction was achieved using a PDA?+?Manitol (?0.7?MPa) medium for both Trichoderma spp. and Bacillus subtilis. Fifty disinfected bean seeds were placed in each petri dish. When the first radicle protrusion appeared in a seed, the other seeds were removed and dried in the laboratory environment for 48?h. Film coating was performed with the addition of the Color Seed^® (150?mL kg^?1) polymer to a treatment solution containing either the Trichoderma spp. or the Rhizoliptus product. Seeds were dried for 48?h in the laboratory. Seeds were covered and treated with one or both organisms. Biopriming with spore or bacterial cell suspensions promoted bean seedling growth, and the other techniques were not required to potentiate these benefits. Covering the primed bean seeds reduced seed quality. Both Trichoderma spp. and Bacillus subtilis promote bean seedling growth, benefitting the seedling even after it becomes independent of the seed reserves.     

Foliar feeding of boron improves the productivity of cotton cultivars with enhanced boll retention percentage

Abstract

Cotton (Gossypium hirsutum L.) is of prime importance because of its quality fiber and edible oil production. Boron (B) is among essential micronutrients for plant growth; it aids in the transfer of sugars and nutrients from leaves to fruit that are involved directly or indirectly in many plant functions. Cotton growth, yield and quality are strongly affected with boron application. A two-year study was conducted to evaluate the impact of foliar applied B (0, 2, 4, 6, 8 and 10?g of B L^?1 of water) on the performance of cotton cultivars (FH-113, MNH-786 and CIM-496). The results indicated that growth, yield and quality traits of cotton were significantly influenced by different levels of foliar applied boron as well as cultivars of cotton. Among cotton cultivars, the yield and quality parameters were superior in cultivar “FH-113.” Foliar application of boron at 6?g L^?1 of water improved leaf area index and leaf area duration and eventually improved the number of bolls per plant, boll retention percentage, average boll weight, lint yield, ginning out turn, fiber length and uniformity ratio of cotton. Foliar application of B at 6?g per liter of water, showed promising results by improving growth and quality parameters and is recommend to enhance the economical yield production of cotton cultivar “FH-113” with improved quality.     

Different pre-sprouting methods for early tuber harvest in potato (Solanum tuberosum L.)

Abstract

Earlier harvest of potatoes (Solanum tuberosum L.) can be achieved by different treatments of the seed tubers. This can be important, for example, in areas with a short growing season and in organic farming. In a pot experiment, different pre-sprouting methods were evaluated for four cultivars. The experiment consisted of (a) untreated seed tubers stored at 4 °C until planting, (b) traditional pre-sprouted tubers (P) and (c) pre-sprouted tubers with stimulation of adventitious root formation (PR). Pre-sprouted seed tubers have earlier and faster tuber formation, but often lower yield than non pre-sprouted tubers if there is no restriction of the growing season. The PR method developed here, where tubers were sprayed with water to stimulate adventitious root formation and give faster development and tuber initiation than conventional pre-sprouting, can be of value when the growing season is restricted or if early harvest is important. Initial emergence of the pre-sprouted potatoes was monitored in two pot experiments. Emergence was faster for the pre-sprouted treatments compared with the control, but there were no significant differences between the two pre-sprouting methods. At harvest, the pre-sprouted treatments gave higher yield than the control for all growing periods, methods and cultivars, although the differences were not significant for every combination. The cultivars Matilda, Cicero, Ovatio and Superb seemed to respond more positively in terms of yield to PR treatments than cv. Ditta. The new method for stimulating adventitious root formation developed here will substantially help growers to achieve earlier harvests.     

Response of cotton root growth and yield to root restriction under various water and nitrogen regimes

Water and nitrogen (N) are two major factors limiting cotton growth and yield. The ability of plants to absorb water and nutrients is closely related to the size of the root system and the rooting space. Better understanding of the physiological mechanisms by which cotton (Gossypium hirsutum L.) adapts to water and N supply when rooting volume is restricted would be useful for improving cotton yield. In this study, cotton was grown in soil columns to control rooting depth to either 60 cm (root‐restriction treatment) or 120 cm (no‐root‐restriction treatment). Four water–N combinations were applied to the plants: (1) deficit irrigation and no N fertilizer (W₀N₀), (2) deficit irrigation and moderate N fertilizer rate (W₀N₁), (3) moderate irrigation and no N fertilizer (W₁N₀), and (4) moderate irrigation and moderate N fertilizer rate (W₁N₁). Results revealed that root restriction reduced root length density (RLD), root volume density (RVD), root mass density (RMD), superoxide dismutase (SOD) activity, nitrate reductase (NR) activity, total plant biomass, and root : shoot ratio. In contrast, root restriction increased aboveground biomass and yield. The RLD, RVD, RMD, and root : shoot ratio decreased in the order W₀N₀ > W₁N₀ > W₀N₁ > W₁N₁ in both the root‐restriction and no‐root‐restriction treatments. However, the opposite order (i.e., W₁N₁ > W₀N₁ > W₁N₀ > W₀N₀) was observed for SOD activity, NR activity, aboveground biomass, and seed yield. Our results suggest that, when N and water supplies are adequate, root restriction increases both root activity and the availability of photosynthates to aboveground plant parts. This increases shoot growth, the shoot : root ratio, and yield.     

Carrot root size distribution in response to biostimulant application

In 2009–2011, in Poland (53°13′N, 17°51′E), field experiments were conducted concerning the influence of biostimulants Kelpak SL and Asahi SL on the size grades of yield of carrot cv. ‘Karotan’. Kelpak SL is produced from seaweed Ecklonia maxima; Asahi SL is composed of nitrophenols. Biostimulants were sprayed from fourth-leaf stage of carrot, once, twice or three times in growing period. Seaweed extract was used at total doses of: 0, 2, 3, 4, 5, 6 and 7?l?ha^?1, while Asahi SL at 1?l?ha^?1. It was found that biostimulants had a favourable effect on total and commercial root yield, but this effect was dependent on the type of preparation, the dose, the time and the number of treatments. The best results in increasing the commercial yield were achieved after a single application of Kelpak SL at doses 2 or 3?l?ha^?1 at the fourth-leaf stage (13.1% and 12.4% respectively, compared to the control). Both biostimulants Kelpak SL and Asahi SL positively affected the root size distribution by increasing the yield of medium roots (1.9–3.8?cm in diameter) as well as large roots (3.8–5.0?cm), by 30.5% and 15.8%, respectively.     

Responses of three switchgrass (Panicum virgatum L.) cultivars to seed priming and differential aging conditions

Abstract

In switchgrass (Panicum virgatum L.) cultivation, rapid and uniform germination is essential because it is one of the most promising candidates for biofuel production. Priming, a seed enhancement technique with solid carriers, can be a useful tool for improving germination characteristics of switchgrass seeds. The objective of this study was to determine the effectiveness of priming on three non-aged and aged switchgrass cultivars of ‘Cave in rock’ ‘Dacotah’, and ‘Kanlow’. Seeds were primed with a synthetic calcium silicate (MicroCel E) and water at 30°C for five days. Seed, carrier and water proportions were 1 g, 0.5 g, and 1.5 mL, respectively. There was a 5% point (pp, Cave in rock), 8 pp (Dacotah), and 19 pp (Kanlow) increase in primed seeds compared with non-treated control seeds. Furthermore, priming decreased mean germination time by 26–36% in all seeds compared with the non-treated control. Accelerated aging was induced by storing seeds for 0, 10, and 21 days at 42°C and 95% relative humidity (RH). Germination percentage decreased and mean germination time increased with the aging. These results suggest that priming is an effective technique to improve the performance of switchgrass cultivars.     

Messung und Simulation der anisothermen Feuchtebewegung in benetzungsgehemmten Mineralböden

Measurement and simulation of nonisothermal moisture movement in water-repellent mineral soils Water repellency often occurs in surface soil horizons, where the temperature may have a significant effect on water movement. Relatively few studies have been conducted to measure the effect of temperature gradients on hydraulic processes in water-repellent soils. The objective of this paper is to analyze the simultaneous impact of hydraulic and thermal gradients on water movement in unsaturated soils. Four sandy soils with organic matter contents between 1.0 and 2.4 percent were used in a laboratory column experiment. The soils had similar particle size distribution and contact angles between 25 and 111 degrees. The water repellency was measured with the “sessile drop method”. The experiments were conducted with open laboratory soil columns. A ceramic plate was placed at the upper end of the soil column to allow water movement from a reservoir, the lower end was closed. The matric potential of ?175 hPa at the upper part of the column was held constant. Simultaneously a constant temperature gradient of approximatly 1.1 °C/cm was applied during the nonisothermal runs. Hydraulic properties of the four soils were determined sequentially at different temperatures (5, 20 and 38°C). The time dependent volumetric water content, matric potential and temperature were measured at five positions in the column. It was found that after steady state was established the water content and matric potential profiles of the four soils differed considerably. A computer code based on the theory of Philip and De Vries (1957) was developed to simulate water and heat transport. For three soils with contact angles of 25–35, 93–108 and 109–111 degrees, respectively, the model performed well when the theoretically calculated thermal vapor difivisivity, D_TV, was multiplied by a factor between two and three. For the slightly water repellent soil with a contact angle between 45 and 83 degrees, however, this factor was about seven to eight. This factor could be the result of a combined impact of the moderate water repellency and the micromorphology of the humic substance.     

Na compound fertilizer stimulates growth and alleviates water deficit in the succulent xerophyte Nitraria tangutorum (Bobr) after breaking seed dormancy

Nitraria tangutorum (Bobr), a typical succulent xerophyte with high level of seed dormancy, is one of the few shrubs found to date that can develop and form fixed dunes in desert regions. Our studies have demonstrated that the strong drought tolerance of the succulent xerophytes was strongly linked to high sodium (Na⁺) accumulation in the photosynthesizing branches (PB) as well as leaves. The study is to explore a method that can rapidly promote the seed germination of N. tangutorum, and then investigate the positive effects of Na compound fertilizer (NaCF) on the growth and drought tolerance of N. tangutorum and ecological environment by short-term pot experiment in a greenhouse and long-term field and pot experiment in a desert environment. The results indicate that the germination rate of seeds obtained a maximum by 69% when seeds were treated with 150 mg L ^?1 gibberellic acid (GA₃) for 48 h followed by soaking in concentrated sulfuric acid (98% H₂SO₄) for 55 min, and then germinated (25/5°C) in darkness for 8 d. After breaking seed dormancy, the NaCF significantly stimulated growth of N. tangutorum and, concomitantly, improved its ability to cope with water deficit (30% of field water capacity) by increasing Na⁺ more than Potassium (K⁺) accumulation for osmotic adjustment in greenhouse and desert conditions. The contribution (take the pot experiment in the desert, for example) of Na⁺ to the osmotic potential (compared with control) varied from 13.9% in plants subjected to diammonium phosphate [(NH₄)₂HPO₄] to, surprisingly, 63.9% in plants grown in the presence of NaCF under water deficit. The distribution characteristics of the total Na⁺ (1620 mg) in the NaCF indicate that 691.2 mg (42.7%) is absorbed by plants, 848.8 mg (52.4%) remained in the pot and 80 mg (4.9%) leached, which accounted for 2.2% of the nursery soil, respectively. The positive effect of NaCF on the drought resistance of N. tangutorum and the ecological environment were also confirmed in the field experiments. These findings suggest that the rapid seed germination technology of N. tangutorum combined with the popularization and application of NaCF can shorten the seed germination period and make the seedling establishment much easier, which may be an effective strategy to restore and reconstruct degraded vegetation in many desert regions.