Half-strength Nutrient Solution Research Articles

Exploring the synergistic effects of melatonin and salicylic acid in enhancing drought stress tolerance in tomato plants through fine-tuning oxidative-nitrosative processes and methylglyoxal metabolism

Enhancement of drought stress (DS) tolerance in plants has been reported with the separate applications of melatonin (MT) and salicylic acid (SA). However, the synergistic effects of their combined application and the exact mechanisms through which they enhance drought tolerance are still not fully understood. The study explored the joint effects of MT and SA on DS tolerance and their implications for oxide-nitrosative processes and methylglyoxal metabolism in tomato plants. To impose DS in tomato plants, they were treated with a 6% polyethylene glycol solution (PEG-6000) in a half-strength nutrient solution. The plants underwent a treatment consisting of individual or combined spraying with 0.5 mM SA and/or 0.1 mM MT every two days for 14 days to relieve the after effects of the PEG-induced stress. The combined MT and SA treatment improved plant drought tolerance, resulting in significant increases in shoot (75%) and root (204%) dry weights. Other improvements included a 141% increase in total chlorophyll content, a 61% increase in Fv/Fm, a 39% increase in Ψl, a 50% increase in RWC, and a 76% increase in proline content compared to DS alone. It also increased non-enzymatic antioxidants (ascorbate and glutathione) and decreased oxidized glutathione under DS. The combined treatment also led to decreased levels of hydrogen peroxide, carbonyl (-CO), and thiol (-SH) groups, indicating the activation of the oxide-nitrosative system. Additionally, the treatment with MT and SA together increased the activity of l-cysteine desulfhydrase (L-CD), resulting in the production of hydrogen sulfide (H2S) and nitric oxide (NO), while decreasing the activity of S-nitroso glutathione reductase, which may have accelerated S-nitrosylation. The synthesis of methylglyoxal (MG) was also reduced by the combined treatment, possibly through the upregulation of the glyoxalase system. Overall, our study presents evidence that the combination of MT and SA treatment can enhance tomato plant tolerance to DS by regulating the oxidative-nitrosative processes and methylglyoxal metabolism.

FERTILIZER CONCENTRATION AND IRRIGATION METHOD AFFECTS GROWTH AND FLOWERING OF TWO BEDDING PLANTS

Zonal geranium (Pelargonium × hortorum ‘Real Mintaka’) and petunias (Petunia × hybrid Hort. Vilm.-Andr. ‘Giove’) were grown in closed soilless systems to evaluate the effects of irrigation system (drip and subirrigation) and nutrient solution concentration (half and full) during spring growing season in terms of substrate electrical conductivity (EC(s)), growth, quality, crop evapotranspiration, and growth index water use efficiency (WUE(GI)). For both crops, at the end of the cultural cycle the highest EC(s) in the upper and lower layers were recorded in plants fertilized with the full strength solution, whereas the effect of irrigation system was less pronounced where the highest EC(s) was recorded in subirrigation but only in the upper layer. The highest EC(s) recorded with subirrigation under full strength nutrient solution on geranium had a negative effect on plant growth parameters (shoot dry weight, root-to-shoot ratio, final leaf area, and growth index) and on number of flowers, while no significant effects were observed for petunia, indicating that this bedding plant can be considered more tolerant to salinity. No significant differences among treatments were recorded for the petunia WUE(GI), whereas for geranium the lowest value of WUE(GI) was observed in the subirrigation treatment using half strength nutrient solution.

Zinc tolerance and uptake by Arabidopsis halleri ssp. gemmifera grown in nutrient solution

Zinc is an essential micronutrient element but its concentrations found in contaminated soils frequently exceed those required by the plant and soil organisms, and thus create danger to animal and human health. Phytoremediation is a technique, often employed in remediation of contaminated soils, which aims to remove heavy metals or other contaminants from soils or waters using plants. Arabidopsis (A.) halleri ssp. gemmifera is a plant recently found to be grown vigorously in heavy metal contaminated areas of Japan and it contained remarkably high amount of heavy metals in its shoots. However, the magnitude of Zn accumulation and tolerance in A. halleri ssp. gemmifera need to be investigated for its use as a phytoremediation plant. A. halleri ssp. gemmifera was grown for 3 weeks into half-strength nutrient solution with Zn (as ZnSO(4)) levels ranging from 0.2 to 2,000 microM. The harvested plants were separated into shoots and roots, dried in the oven, and ground. The plant tissue was digested with nitric-perchloric acid, and the Zn concentration in the digested solution was measured by atomic absorption spectrophotometer. The results showed no reduction in shoot and root dry weight when plants were grown at 0.2 to 2,000 microM Zn in the solution. The highest Zn concentration measured in the shoots was 26,400 mg kg(-1) at 1,000 microM Zn, while in the roots, it was 71,000 mg kg(-1) at 2,000 microM Zn treatment. Similar to the Zn concentration in plant parts, maximum Zn accumulation of 62 mg plant(-1) in the shoots and 22 mg plant(-1) in the roots was obtained at 1,000 and 2,000 microM Zn in the solution. The percentage of Zn translocation in shoot varied from 69% to 90% of the total Zn, indicating that the shoot was the major sink of Zn accumulation in this plant. The results of this study indicate that the growth of A. halleri ssp. gemmifera was not affected by the Zn level of up to 2,000 microM in the nutrient solution. The concentration of Zn found in shoot indicated that A. halleri ssp. gemmifera has an extraordinary ability to tolerate and accumulate Zn and hence a good candidate for the phytoremediation of Zn-polluted soil. Based on the results presented in this study and earlier hydroponics, and field study, A. halleri ssp. gemmifera seems to be a potential heavy metals hyperaccumulator, and could be recommended to use for phytoremediation of Cd- and Zn-contaminated soils.

The Influence of Drip Irrigation or Subirrigation on Zucchini Squash Grown in Closed-loop Substrate Culture with High and Low Nutrient Solution Concentrations

Zucchini plants (Cucurbita pepo L. cultivar Afrodite) were grown during a summer–fall season in closed-soilless systems using a mixture peat–pumice to evaluate the effects of irrigation system (drip irrigation and subirrigation) and nutrient solution concentration (half = 1 dS·m−1 and full = 2 dS·m−1) in terms of substrate electrical conductivity (ECs) using the dilution 1:1.5 media:water method, growth, yield, leaf mineral composition, fruit quality, and mineral solution composition. At the end of the cultural cycle, the highest ECs at the upper (0 to 7.5 cm) and lower (7.5 to 15.0 cm) layers were recorded with subirrigation using a full nutrient solution concentration. The highest plant growth, yield, and leaf macroelements concentration (nitrogen, phosphorus, and potassium) were recorded in both irrigation systems using a full-strength solution, followed by drip irrigation, and finally by subirrigation treatment using a half-strength nutrient solution. Fruit yield, fruit mineral composition (phosphorus, potassium, calcium, and magnesium), and leaf macroelements concentration (nitrogen, phosphorus, potassium, and magnesium) were substantially reduced when the concentrations of macronutrients in the feed solution were lowered to 50% of control. Using half-nutrient solution concentration, the marketable yield reduction was more pronounced with subirrigation (58%) than with drip irrigation (42%). The variation of the macronutrient and EC in the solution during the growing cycle was less pronounced in the subirrigation than with the drip irrigation system, which represents an important aspect for the simplification of the closed-loop management of the nutrient solution.

Effects of nutrition and Bacillus amyloliquefaciens on tomato (Solanum lycopersicum, L.) growing in perlite

Plant growth-promoting rhizobacteria (PGPR) are free-living bacteria that, as their name suggests, promote plant growth. However, they can also be of help in the biological control of plant diseases. This study reports the effects of two different commercially available strains of Bacillus amyloliquefaciens (FZB24 and FZB42) on tomato production in open and closed systems in the presence of different amounts of nutrients. Three factors were tested: (1) the type of nutrition system (open or closed), (2) the concentration of the nutrient solution (full or half strength), and (3) the PGPR applied (either B. amyloliquefaciens FZB24 or B. amyloliquefaciens FZB42, or a no-PGPR control). Perlite was used as the growth medium. Variables related to water use efficiency, yield and fruit quality were assessed. The use of half strength nutrient solution was sufficient for full growth in the open system in both spring and autumn seasons. However, the same strength nutrient solution was associated with reduced yields in the closed system during the autumn season. The application of either strain of B. amyloliquefaciens increased the yield of the tomato plants by 8-9% in the open system in the spring, whereas they had an adverse effect on yield in the closed system under half strength nutrient solution conditions during the autumn.

Proteomic analysis of salt stress responses in foxtail millet ( Setaria italica L. cv. Prasad) seedlings

Soil salinity is one of the major abiotic stresses limiting crop productivity and the geographical distribution of many important crops worldwide. To gain a better understanding of the salinity stress responses at molecular level in dry land small millet crop, foxtail millet ( Setaria italica L.), we carried out a comparative proteomic analysis. Foxtail millet seeds were surface sterilized and germinated in Petri plates lined with filter paper. Salt stress was imposed by serving the Hoagland half strength nutrient solution with 100, 150 and 200 mM NaCl (saline treatment) or without (control) and maintained in dark for 7 days. Salt treatment resulted in reduced seedling growth and dry mass. The temporal changes in total protein profile of foxtail millet seedlings under different salt stress regimes were studied using two-dimensional electrophoresis. Among ∼175 protein spots reproducibly detected on each gel, some were up-regulated and few others were down-regulated at least at one time point. Mass spectrometry analysis allowed the identification of 29 differentially expressed proteins including well-known salt responsive proteins. Several proteins showed up- and down-regulation during salt stress. MALDI-TOF/MS analysis and database searching of some of the identified proteins indicated that the proteins are known to be involved in several processes, i.e., of signal transduction, photosynthesis, cell wall biogenesis, stress related and several metabolisms like energy, lipid, nitrogen, carbohydrate and nucleotide metabolisms, where others are of unknown function. In conclusion, our study provides new insights into salt stress responses in foxtail millet and demonstrates the advantages of proteomic analysis.

Yield and fiber quality of Upland cotton as influenced by nitrogen and potassium nutrition

Nutrient stress in Upland cotton ( Gossypium hirsutum L.) depresses lint yield, particularly of late-season fruit (bolls), and may disrupt fiber development. A 2-year (1999 and 2000) study was conducted outdoors in large pots to determine individual effects of nitrogen (N) and potassium (K) stress at flowering stage on lint yield and fiber quality. Treatments were half-strength nutrient solution from emergence to crop maturity (control), 20% and 0% of control N from first flower onward, and 20% and 0% of control K from first flower onward in 1999 and first square onward in 2000. Leaf N and K were determined every 2–3 days from an uppermost, fully expanded leaf on the main-stem of five plants selected at random. Mature bolls were harvested from sympodial (fruiting) branches only and grouped according to week of anthesis across a 35-day flowering period, providing five flowering groups, from which fiber length, strength, and micronaire were determined. Fiber length was not consistently altered by stress, suggesting early stages of fiber development were indirectly affected by plant N and K status. Nitrogen deficiency decreased yield through early termination of reproductive growth. In 1999, although flowering group four of N-deficient cotton had low length, strength, and micronaire, values for weighted-sum micronaire (whole-plant micronaire) increased under N stress by about 12% in 0% N treatment and about 18% in 20% N treatment. In general, N and K stress had opposite effects on weighted-sum micronaire. The year by N treatment interaction was significant for weighted-sum strength, due to weak fibers in N-deficient cotton in 1999, but no treatment difference in 2000. Apparently, crop response to N stress was influenced by environment, as flowering groups with low quality fiber also comprised a large fraction of total lint, and thus placed heavy demands on plant N and carbohydrate reserves. Severe K deficiency in 2000 decreased yield and lint weight boll −1, and micronaire values of 3.7 or less were evident in flowering groups two, three and four. Results support evidence that N stress indirectly affects cotton growth, as N deficiency decreased fiber length, strength and micronaire primarily in flowering groups with large percentage of bolls. Results from 2000 support evidence that K deficiency adversely affects reproductive growth, boll weight, and sugar translocation in cotton.

Nitrogen deficiency effects on plant growth, leaf photosynthesis, and hyperspectral reflectance properties of sorghum

An experiment was conducted under outdoor pot-culture conditions to determine effects of nitrogen (N) deficiency on sorghum growth, physiology, and leaf hyperspectral reflectance properties. Sorghum (cv. DK 44C) was seeded in 360 twelve-litre pots filled with fine sand. All pots were irrigated with half-strength Hoagland's nutrient solution from emergence to 25 days after sowing (DAS). Thereafter, pots were separated into three identical groups and the following treatments were initiated: (1) the control (100% N) continued receiving the half-strength nutrient solution; (2) reduced N to 20% of the control (20% N); and (3) withheld N from the solution (0% N). Photosynthetic rate (Pn), chlorophyll (Chl) and N concentrations, and hyperspectral reflectance of the uppermost, fully expanded leaves were determined at 3- to 4-day-interval from 21 to 58 DAS during the N treatments. Plants were harvested 58 DAS to determine effects of N deficiency on leaf area (LA), biomass accumulation, and partitioning. Nitrogen deficiency significantly reduced LA, leaf Chl content and Pn, resulting in lower biomass production. Decreased leaf Pn due to N deficiency was mainly associated with lower stomatal conductance rather than carboxylation capacity of leaf chemistry. Among plant components of dry weights, leaf dry weight had the greatest and root dry weight had the smallest decrease under N deficiency. Nitrogen-deficit stress mainly increased leaf reflectance at 555 ( R 555) and 715 nm ( R 715) and caused a red-edge shift to shorter wavelength. Leaf N and Chl concentrations were linearly correlated with not only the reflectance ratios of R 405/ R 715 ( r 2 = 0.68 ***) and R 1075/ R 735 ( r 2 = 0.64 ***), respectively, but also the first derivatives of the reflectance (d R/d λ) in red edge centered 730 or 740 nm ( r 2 = 0.73–0.82 ***). These specific reflectance ratios or d R/d λ may be used for rapid and non-destructive estimation of sorghum leaf Chl and plant N status.

Response of Sultana vines ( V. vinifera L.) on six rootstocks to NaCl salinity exposure and recovery

One-year-old Sultana ( Vitis vinifera L.) vines, own-rooted and grafted on 41B, 110R, 140Ru, 1103P and SO 4 were grown in sand–perlite mixture (1:1) irrigated with half-strength nutrient solution containing 5, 25, 50 and 100 mM of NaCl. Growth, tissue mineral content and leaf gas exchange response to salt treatment and subsequent recovery were examined over a 70-day period. Shoot growth, leaf area and total dry weight were significantly reduced ( P<0.05) at all salinity levels. Tissue salt content increased significantly with increasing salinity, Cl − being always higher than Na +. Photosynthetic rate ( P n) and stomatal conductance ( g s) were greatly reduced by salinity and highly correlated with leaf Cl − content. Own-rooted vines exhibited higher dry matter production and photosynthetic rates than grafted vines, despite the higher Cl − and Na + content. During recovery, vines previously treated with 50 and 100 mM NaCl exhibited photosynthetic rates and stomatal conductances similar to the control, although laminae Na + and Cl − content continued to increase. Our results showed that own-rooted ‘Sultana’ vines ( V. vinifera) can cope better with high salinity followed by those grafted on 1103P, 140Ru, 110R, SO 4 and 41B rootstocks.

293 Genotypic and Temporal Variation in Nitrate Uptake Rate by Kentucky Bluegrass

Turfgrass cultivars that have superior nitrate uptake ability are needed for the protection of ground water from pollution by excess nitrate. Information on temporal variation of nitrate absorption is also needed to enhance the environmental safety of turfgrass N fertilization programs. Our objectives were to evaluate Kentucky bluegrass (Poa pratensis L.) cultivars for their differences in nitrate uptake rate (NUR) and temporal variation in NUR. Six cultivars (Barzan, Blacksburg, Connie, Dawn, Eclipse, and Gnome) were propagated from individual tillers and six plants of each cultivar were generated from one mother plant. Plants were grown in silica sand, mowed weekly, and watered daily with half-strength modified Hoagland's nutrient solution containing 1 mM nitrate. When 5 months old, the plants were excavated, the roots were washed to remove sand, and the plants were transferred to 120-mL black bottles. After 24 hours in tap water, the plants were supplied with half-strength nutrient solution containing 0.5 mM nitrate, and the solutions were replaced daily for 8 days. NURs expressed as micromoles per plant per hour were calculated from solution nitrate depletion data. Significant genotypic differences in NUR were found: `Blacksburg' &gt; `Connie' &gt; `Dawn' &gt; `Barzan' = `Eclipse' &gt; `Gnome'. Significant temporal variation in NUR was also found, with NUR on the second day more than the first day after tap water. A significant interaction was noted between genotype and time. Temporal variation was greatest in `Blacksburg', while none noted in `Connie' and `Eclipse'. In `Barzan' and `Gnome', NUR on the last day was higher than the first day.

EFFECT OF DIFFERENT CONCENTRATIONS OF NUTRIENT SOLUTIONS ON THE GROWTH, YIELD, AND QUALITY OF BASIL

This experiment was carried out to ascertain optimal hydroponic conditions for top quality basil production. Sweet basil (Ocimum basilicum), opal basil (Ocimum basilicum purpurascens), and bush basil (Ocimum minimum) were grown in a hydroponics culture system (NFT) with a nutrient solution developed by the European Vegetable R & D Center in Belgium. Four different ionic strength solutions were used (half, one, two and three times strength). Although sweet, opal and bush basil belong to the same genus (Ocimum) and the same family (Labiateae), they responded differently to these concentrations of nutrient solution in terms of growth and internal qualities. The best growth of sweet basil was obtained with a half strength nutrient solution, and for opal basil, and for bush basil with standard strength solutions, respectively. The essential oil was extracted by steam distillation.