Reduction In Dry Matter Yield Research Articles

Basil (Ocimum basilicum) Landraces Can Be Used in a Water-Limited Environment

Basil (Ocimum basilicum L.) is a member of the Labiatae family and is one of the most widely consumed aromatic and medicinal plants in many countries due to its numerous properties and uses. The objective of the study was to determine whether landraces are better adapted to water-limited environments compared to commercial cultivars. Irrigation levels and genotypes affected plant height and leaf area index, with 25% and 33% higher values observed under complete irrigation, respectively. Additionally, limited water availability resulted in a 20% reduction in dry matter yield and a 21% reduction in essential oil yield over the three years in all of the genotypes tested, specifically in the lower irrigation treatment (d40), compared to the control treatment (d100). The landraces that performed the best under limited water supply were Athos white spike (AWS) and Gigas white spike (GWS), indicating their suitability for environments with limited water resources. The results demonstrate that there are landraces that can be utilized in dryland climates with appropriate water management, enabling water conservation and utilization of fields in water-scarce areas for irrigation purposes.

Biomass production, water use efficiency and nutritional value parameters of sorghum ( Sorghum bicolor L.) genotypes as affected by seed hydro-priming and transplanting

To investigate hydropriming and transplanting effect on biomass and nutritional content of forage sorghum, a two-year field experiment was conducted in the semiarid condition of Iran. Experimental factor consisted of planting dates (July-1st, July-11th, July-23rd, August-1st) in the main plot and the factorial combination of planting methods (direct planting, hydropriming, transplanting) with cultivars (Speedfeed and Pegah) in the subplot. Planting date postponement from 1st of July to 10th of July, 23rd of July, and 1st of August, respectively, caused 16.1, 32.5 and 47.2% reduction in dry matter yield (DMY) and 7.4, 20.2, and 35.1% reduction in water use efficiency of DMY production (WUEDMY). Hydropriming and transplanting produced 23.6 and 22.4% more DMY, 24.5 and 21.8% more WUEDMY, 24 and 16.3% more crude protein yield, 22.7 and 20.9% more digestible dry matter (DDM) yield, and 22.2 and 20.1% more metabolic energy (ME) yield, compared to the direct planting. Hydropriming compared to direct planting caused 29% increase in plant growth rate and utilized growing season more productively than transplanting for DMY production. Conclusively, hydropriming and transplanting compensated for delay in planting through enhancing and accelerating germination and plant development but, applying hydropriming on Speedfeed and planting in July-1st caused the highest DMY, WUEDMY and the yield of nutritive parameters.

Biomass production, water use efficiency and nutritional value parameters of sorghum (Sorghum bicolor L.) genotypes as affected by seed hydro-priming and transplanting

To investigate hydropriming and transplanting effect on biomass and nutritional content of forage sorghum, a two-year field experiment was conducted in the semiarid condition of Iran. Experimental factor consisted of planting dates (July-1st, July-11th, July-23rd, August-1st) in the main plot and the factorial combination of planting methods (direct planting, hydropriming, transplanting) with cultivars (Speedfeed and Pegah) in the subplot. Planting date postponement from 1st of July to 10th of July, 23rd of July, and 1st of August, respectively, caused 16.1, 32.5 and 47.2% reduction in dry matter yield (DMY) and 7.4, 20.2, and 35.1% reduction in water use efficiency of DMY production (WUEDMY). Hydropriming and transplanting produced 23.6 and 22.4% more DMY, 24.5 and 21.8% more WUEDMY, 24 and 16.3% more crude protein yield, 22.7 and 20.9% more digestible dry matter (DDM) yield, and 22.2 and 20.1% more metabolic energy (ME) yield, compared to the direct planting. Hydropriming compared to direct planting caused 29% increase in plant growth rate and utilized growing season more productively than transplanting for DMY production. Conclusively, hydropriming and transplanting compensated for delay in planting through enhancing and accelerating germination and plant development but, applying hydropriming on Speedfeed and planting in July-1st caused the highest DMY, WUEDMY and the yield of nutritive parameters.

Residual bioavailability of nickel in nickel spiked sandy loam soil: Impact on swede rape (Brassica napus L.) growth and uptake of micronutrients

In screenhouse experiment, a sandy loam soil (Typic Ustipsamment) was spiked with six levels of nickel (Ni) viz. 0, 5, 10, 25, 50, 100 mg kg−1 soil to investigate residual bioavailability of Ni and its impact on Swede rape grown after rice. The residual effect of Ni was investigated on growth of swede rape and uptake of micronutrients by it. Swede rape [Brassica napus (L.) Czern.] was grown for 60 days for dry matter accumulation, content of nickel and micronutrients. A linear and significant decrease in dry matter yield (DMY) was observed with the residual effect emanating from each successive level of Ni contamination except for that observed under 5 mg kg−1 Ni spiking. Maximum reduction in DMY (50%) was observed at 100 mg Ni kg−1 soil contamination level as compared to control. Nickel uptake by Swede rape increased substantially from 15.3 pg pot−1 in control to 397.8 pg pot−1 at 100 mg Ni kg−1 soil. Nickel spiking reduced the concentration of micronutrients in Swede rape, but significant reduction occurred only for iron at levels higher than 10 mg kg−1 soil. However, the uptake of iron, manganese, and zinc registered a significant decline at 5 mg Ni kg−1 soil and successive higher rates. Even after the harvest of Swede rape, 14.2 mg Ni kg−1 soil remained in the soil spiked with 100 mg Ni kg−1. This suggests that several cropping cycles would be required to make a contaminated soil safe for cultivation.

Effect of Salinity on Emergence and Early Growth Stages of Aromatic and Non-Aromatic Rice (Oryza sativa L.) Genotypes

Salinity hampers the production of many field crops in the region including rice (Oryza sativa L.), while commonly classified as salt sensitive within the same species, the level of sensitivity varies between genotypes. This study investigated the salinity tolerance of 28 rice genotypes, including 9 aromatics and 19 non-aromatics. Sixty seeds of each genotype were initially sown in trays (24x18 inches) during the 1st week of June, by of using four salt treatments (0, 40, 80 and 120 mM NaCl+CaCl2 @ 20:1). The experiment was laid down in a completely randomized design with four replicates in laboratory conditions, at Shah Abdul Latif University Khairpur, Sindh, for the period of twenty-five days. A significant reduction in agro-morphological parameters was observed against all salinity levels. Based on reduction in dry matter yield, all rice genotypes were found tolerant at 40 mM. Eleven rice genotypes were found tolerant, fourteen were moderately tolerant, one was moderately sensitive and remaining two genotypes were found sensitive at 80 mM salinity level. Furthermore, none of the genotypes were able to with stand 120 mM of salinity. The genotypes Khushboo, DR-83 and Mahek performed meager and showed more than 50% reduction over control and categorised as sensitive, with the genotypes Latifee, DR-67 and DR-92, DR-51 and IR-6 are categorised as tolerant with a reduction of less than 20% over control based on dry matter yield reduction against all salinity treatments at the early seedling stage. However, these genotypes cannot be justified as tolerant only on the basis of their improved performance at early growth stage. Hence, these genotypes are suggested to be studied further at other advanced growth stages up to maturity to evaluate their response under a saline environment.
 

Feasibility of Moderate Deficit Irrigation as a Water Conservation Tool in California’s Low Desert Alfalfa

Irrigation management practices that reduce water use with acceptable impacts on yield are important strategies to cope with diminished water supplies and generate new sources of water to transfer for other agricultural uses, and urban and environmental demands. This study was intended to assess the effects of moderate water deficits, with the goal of maintaining robust alfalfa (Medicago sativa L.) yields, while conserving on-farm water. Data collection and analysis were conducted at four commercial fields over an 18-month period in the Palo Verde Valley, California, from 2018–2020. A range of deficit irrigation strategies, applying 12.5–33% less irrigation water than farmers’ normal irrigation practices was evaluated, by eliminating one to three irrigation events during selected summer periods. The cumulative actual evapotranspiration measured using the residual of energy balance method across the experimental sites, ranged between 2,031 mm and 2.202 mm, over a 517-day period. An average of 1.7 and 1.0 Mg ha−1 dry matter yield reduction was observed under 33% and 22% less applied water, respectively, when compared to the farmers’ normal irrigation practice in silty loam soils. The mean dry matter yield decline varied from 0.4 to 0.9 Mg ha−1 in a clay soil and from 0.3 to 1.0 Mg ha−1 in a sandy loam soil, when irrigation water supply was reduced to 12.5% and 25% of normal irrigation levels, respectively. A wide range of conserved water (83 to 314 mm) was achieved following the deficit irrigation strategies. Salinity assessment indicated that salt buildup could be managed with subsequent normal irrigation practices, following deficit irrigations. Continuous soil moisture sensing verified that soil moisture was moderately depleted under deficit irrigation regimes, suggesting that farmers might confidently refill the soil profile following normal practices. Stand density was not affected by these moderate water deficits. The proposed deficit irrigation strategies could provide a reliable amount of water and sustain the economic viability of alfalfa production. However, data from multiple seasons are required to fully understand the effectiveness as a water conservation tool and the long-term impacts on the resilience of agricultural systems.

External detoxification mechanism of corn plants exposed to cadmium stress

ABSTRACT Understanding the processes crops use to detoxify heavy metals (HMs), are critical in crops production and environmental management. The role of organic acids (OAs) exudation as an external mechanism of corn plants to detoxify cadmium (Cd) toxicity was examined in a hydroponic experiment. Treatments consisted of four levels of Cd concentrations (0, 10, 25 and 40 µM) and four exposure time periods (2, 4, 8 and 16 days) to Cd stress. The increased Cd concentration increased the release rates of OAs, namely oxalic, citric and acetic acids. Oxalic acid was the dominate OA (≥80% of the total OAs measured) released by the plants. Releasing OAs increased Cd uptake by plants via complexing Cd ions in nutrient solution. OAs exudation rate decreased by increasing exposure time periods to Cd stress. The decreased exudation rate minimised the adverse effect of Cd stress on plant growth. As a result, the percentage of dry matter yield reduction rates decreased by increasing corn plants exposure time periods to Cd stress. In conclusion, results indicated that corn roots OAs exudation rates play an important role in detoxifying Cd toxicity by complexing Cd ions and accumulate it in root vacuoles to protect cell metabolism and plant growth.

Effect of Abiotic Stress on Irrigated Maize Forage Yield as Compared to Sorghum

A study was conducted in Sudan (Africa) during the summer and winter seasons (2013 – 2014) at two locations: Shambat (normal soils) and Soba (salt affected soils). Nine maize (ZeamaysL.) and sorghum (Sorghum bicolor(L.) Moench) cultivars were studied under two watering regimes arranged in split plot experiment in randomized complete block design. The eight test-environments created by the combination of locations, seasons and watering regimes were used to investigate the effect of salt, water and heat stresses on forage yield and some related traits. The results showed that separate and combined stress factors significantly reduced forage yield. The greatest reduction in dry matter yield caused by one factor was shown by salt stress (29.6%) and the least reduction was caused by heat stress (3.9%). Water stress coupled with either heat or salt stress caused the greater reduction in yield (37.0%-43.3%) than the combination of the other factors. Full stress caused 53.8% yield reduction. Days to tasseling was significantly reduced by heat stress whereas water and salt stress showed no significant effect on tasseling duration. Full stress caused the greatest effect on days to tasseling. Plant height and stem diameter were significantly reduced by salt and water stress. Two hybrids kept top rank in yield through most abiotic stress levels showing resilience to unfavorable environments. All maize genotypes significantly outyielded the sorghum check under no heat stress (winter sowing) regardless the effect of salt and water stresses while the opposite is true under the heat stress (summer sowing). It was concluded that salt and water stress are the major abiotic stresses limiting forage maize production. Maize tolerate better reduction in temperature than dose sorghum while the latter tolerate better salt and water stresses than dose maize. Forage maize could be competitively grown during summer if water and salt stresses are avoided

Improving grass silage production with controlled traffic farming (CTF): agronomics, system design and economics

Grassland silage management is generally semi-organised with no conscious attempt to re-use wheel ways as with arable fields. The total number of machine passes can be 15 or more with normal traffic (NT) systems resulting in potentially large areas of a field suffering from direct damage to the crop and soil. Literature suggests there can be grass dry matter yield reductions of 5 to 74% under NT through compaction and sward damage, with a mean of 13% in the UK. Commercially available grass forage equipment with widths of 3 to 12 m set up for controlled traffic farming (CTF) could reduce trafficked areas (which is typically 90% to 80% for NT) to 40% to 13% for CTF. This study compared grass dry matter yield between CTF and NT for a three-cut silage system based on a 9 m working width in a permanent silage field in the southwest of Scotland, UK in 2015. Results showed a 13.5% (0.80 t ha−1) increase in yield for CTF for the 2nd and 3rd cuts combined. The CTF trafficked area covered was 57% less than the NT system (30.4% compared to 87.4%) over the three silage cuts. An economic analysis based on a 13% increase in dry matter yield (for 2- and 3-cut systems) and a reduction in trafficked area from 80% (for NT) to between 45% and 15% (for CTF), increased the yield by between 0.53 t ha−1 and 1.36 t ha−1 for 2- and 3-cut systems, respectively with an equivalent grass value of between £38 ha−1 and £98 ha−1. Introducing CTF for a multi-cut grass silage system is cost-effective by increasing yields due to a reduction in compaction and sward damage.

Radiation use efficiency, chemical composition, and methane yield of biogas crops under rainfed and irrigated conditions

For biomethane production, the cup plant (Silphium perfoliatum L.) is considered a promising alternative substrate to silage maize (Zea mays L.) due to its high biomass potential and associated ecological and environmental benefits. It has also been suggested to grow cup plant on less productive soils because of its presumed drought tolerance, but robust information on the impact of water shortage on biomass growth and substrate quality of cup plant is rare. Therefore, this study assesses the effects of soil water availability on the chemical composition and specific methane yield (SMY) of cup plant. Furthermore above-ground dry matter yield (DMY) was analysed as a function of intercepted photosynthetic active radiation (PAR) and radiation use efficiency (RUE). Data were collected in a two-year field experiment under rainfed and irrigated conditions with cup plant, maize, and lucerne-grass (Medicago sativa L., Festuca pratensis Huds., Phleum pratense L.). The cup plant revealed a slight decrease of −6% in the SMY in response to water shortage (less than 50% of plant available water capacity). The average SMY of cup plant [306 l (kg volatile solids (VS))−1] was lower than that of maize [362 l (kg VS)−1] and lucerne-grass [334 l (kg VS)−1]. The mean drought-related reduction of the methane hectare yield (MHY) was significantly greater for cup plant (−40%) than for maize (−17%) and lucerne-grass (−13%). The DMY reduction in rainfed cup plant was mainly attributed to a more severe decrease in RUE (−29%) than for maize (−16%) and lucerne-grass (−12%). Under water stress, the mean cup plant RUE (1.3 g MJ−1) was significantly lower than that of maize (2.9 g MJ−1) and lucerne-grass (1.4 g MJ−1). Compared to RUE, the reduced PAR interception was less meaningful for DMY in rainfed crops. Hence, the cup plant is not suitable for growing on drought prone lands due to its high water demand required to produce reasonably high MHYs.

The impact of drought stress on the yields and food value of selected forage grasses

<p>The aim of the study was to compare yields and nutritional value of selected species and cultivars of forage grasses under the optimal moisture conditions and long-term drought stress. The regenerative capacity of plants after dehydration was also assessed. The pot experiment was conducted in years 2009–2010 in IUNG-PIB’s greenhouse in Puławy, Poland. Nine cultivars of four species: <em>Dactylis glomerata</em> (‘Amera’, ‘Minora’), <em>Festuca pratensis</em> (‘Skra’, ‘Fantazja’), <em>Festulolium braunii</em> (‘Felopa’, ‘Agula’, ‘Sulino’), and <em>Lolium multiflorum</em> (‘Gisel’, ‘Lotos’) were investigated in well-watered conditions (70% field water capacity – FWC) and under a long-term drought stress (40% FWC).</p><p>The study showed that stress caused by soil moisture deficiency significantly reduced yields of <em>D. glomerata</em>, <em>F. pratensis</em>, <em>F. braunii</em>, and <em>L. multiflorum</em>. The total yield of dry matter under stress conditions was about 31% lower, compared to the performance achieved on the optimally moisturized treatment. The smallest reduction in dry matter yield under the conditions of water deficit was recorded for <em>D. glomerata</em>, which makes it the most resistant to stress, followed by <em>F. pratensis</em>. The resistance of <em>F. braunii</em> and <em>L. multiflorum</em> to stress was similar and significantly lower. There was a various response of different grasses to the water stress. On the basis of the value of the DSI (drought susceptibility index), the tested cultivars were ranked depending on the sensitivity to drought, starting with the most resistant cultivar: ‘Minora’, ‘Skra’, ‘Fantazja’, ‘Amera’, ‘Sulino’, ‘Agula’, ‘Gisel’, ‘Lotos’, and ‘Felopa’. The digestibility of dry matter and nutrient value of the grasses depended on both the level of soil moisture and grass species. Under the water stress, the digestibility and protein value increased compared to the control objects. <em>Lolium multiflorum</em> and <em>F. braunii</em> had the best nutritional value, while <em>D. glomerata</em> – the weakest.</p>

Effect of Inorganic Anions on The Bioavailability of Lead to Indian Rape in A Lead Spiked Loamy Sand Soil

A greenhouse pot experiment was conducted to study the influence of different inorganic anions on growth and lead (Pb) content of Indian rape (Brassica compestris var. Toria) in a Pb spiked loamy sand soil. Soil was artificially contaminated with four levels of Pb (0, 50, 100, 200 mg Pb kg−1 soil). Potassium salts of four anions viz. H2PO4−, Cl−, SO42-, CO32- were applied to soil at four rates viz. 0, 60, 120 and 240 mg kg−1 soil. Soil was equilibrated for 30 days and Indian rape was grown for 60 days as a potherb. The results showed a significant increase in mean DTPA-Pb with increase in Pb contamination and it increased from 0.3 in control to 92.2 mg Pb kg−1 soil in 200 mg Pb kg−1 treated soil. Addition of H2PO4− and CO32- resulted in a decrease of DTPA-Pb but addition of Cl−and SO42- resulted in an increase in the DTPA-Pb. The dry matter yield (DMY) of Indian rape at 60 days was significantly reduced by the addition of increasing amounts of Pb but the magnitude of reduction in DMY with Pb contamination decreased with the addition of H2PO4− and CO32- anions but increased with the addition of Cl−. Similarly, the Pb content of plants also increased linearly and significantly with increase in Pb contamination levels but decreased with the addition of H2PO4 and CO32-anions. The results suggested that addition of H2PO4 and CO32-anions lowered the bioavailability and increased the geochemical stability of soil Pb, indicating their potential for in situ remediation in Pb-contaminated soils.

Biomass and quality changes of forages along land use and soil type gradients in the riparian zone of Lake Naivasha, Kenya

The recession of the water level of Lake Naivasha has incrementally exposed land surfaces creating a chronosequential transect representing durations of 1–30 years of exposure to grazing. This chronosequence provides a unique model to study the effects of land use duration on resource availability and resource base quality. Particularly, pasture quality changes in the riparian land of tropical fresh water lakes have so far not been studied. We assessed the effect of the duration of exposure to grazing on the biomass production, crude protein content and energy quality of pastures in a 4×4 latin square design (4 chronosequence positions×4 soil types). Species composition was recorded and biomass was sampled at monthly intervals from February to August 2011. Soil moisture was recorded using frequency domain reflectometry sensors. Vegetation samples were analyzed for dry matter, nitrogen and metabolizable energy. Increased land use duration favored a shift in species dominance from Pennisetum clandestinum to Cynodon plectostachyus, which was associated with a reduction in dry matter yield and increased plant nitrogen content. All measured variables tended to be higher in soils formed on alluvial than in those formed on lacustrine deposits. Increased soil N and gravimetric moisture content stimulated biomass accumulation. The crude protein yield and metabolizable energy changed with phenological stages of the pasture and declined significantly towards maturity (seed setting of grasses). Continuous grazing and reduced soil moisture content, both during low rainfall and increased distance from the lake shore, affected the composition of pasture grasses as well as forage yield and quality. This may thus differentially affect the suitability of the riparian land as pasture ground and feed resource area for grazing animals.

Effect of Salt Stress on Germination and Growth Parameters of Rice (<i>Oryza sativa</i> L.)

The response of eight varieties of Oryza sativa L. (‘NERICA 1’, ‘NERICA 5’, ‘NERICA 12’, ‘NERICA 19’, ‘IR 29’, ‘IR 20’, ‘IWA 11’, and ‘POKKALI’, a salt tolerant check) against four salinity levels (0, 5, 10, and 15 ds m-1) were studied at germination and early growth stages. Data were analyzed using Statistical Analytical System (SAS) and means were separated by Duncan Multiple Range Test (DMRT) for Final Germination Percentage (FGP), Speed of Germination (SG), Germination Energy Percentage (GE%), shoot and root length and root and shoot dry weight. Based on dry matter yield reduction, rice varieties were classified as tolerant (T), moderately tolerant (MT), moderately susceptible (MS) or susceptible (S). Germination was not recorded at 20 ds m-1 salt concentration in all cultivars. Salinity decreased FGP, SG, GE% and led to reduction in shoot and root length and dry weight in all varieties and the magnitude of reduction increased with increasing salinity stress. Rice varieties ‘NERICA 12’, ‘IR 20’, ‘IWA 11’ and ‘NERICA 19’ showed greater salt tolerance during germination (germinated at 10 ds m-1 salinity). However, ‘NERICA 1’, ‘IR 29’, and ‘IR 20’ performed better based on dry matter yield reduction. The result suggested that ‘NERICA 1’, ‘IR 29’, and ‘IR 20’ might be used for further study of salinity effect on growth processes and physiological consequences at advanced stage of growth. The physiological responses of rice plants to salinity at various developmental stages are therefore critical for identifying salinity tolerance in the cultivars.

Effect of Salt Stress on Germination and Growth Parameters of Rice (<i>Oryza sativa</i> L.)

The response of eight varieties of Oryza sativa L. (‘NERICA 1’, ‘NERICA 5’, ‘NERICA 12’, ‘NERICA 19’, ‘IR 29’, ‘IR 20’, ‘IWA 11’, and ‘POKKALI’, a salt tolerant check) against four salinity levels (0, 5, 10, and 15 ds m-1) were studied at germination and early growth stages. Data were analyzed using Statistical Analytical System (SAS) and means were separated by Duncan Multiple Range Test (DMRT) for Final Germination Percentage (FGP), Speed of Germination (SG), Germination Energy Percentage (GE%), shoot and root length and root and shoot dry weight. Based on dry matter yield reduction, rice varieties were classified as tolerant (T), moderately tolerant (MT), moderately susceptible (MS) or susceptible (S). Germination was not recorded at 20 ds m-1 salt concentration in all cultivars. Salinity decreased FGP, SG, GE% and led to reduction in shoot and root length and dry weight in all varieties and the magnitude of reduction increased with increasing salinity stress. Rice varieties ‘NERICA 12’, ‘IR 20’, ‘IWA 11’ and ‘NERICA 19’ showed greater salt tolerance during germination (germinated at 10 ds m-1 salinity). However, ‘NERICA 1’, ‘IR 29’, and ‘IR 20’ performed better based on dry matter yield reduction. The result suggested that ‘NERICA 1’, ‘IR 29’, and ‘IR 20’ might be used for further study of salinity effect on growth processes and physiological consequences at advanced stage of growth. The physiological responses of rice plants to salinity at various developmental stages are therefore critical for identifying salinity tolerance in the cultivars.

10.5937/ratpov51-5571 = Effect of genotype and applied management on alfalfa yield and quality

It is essential to apply advanced management for successful production of alfalfa hay with premium quality (high content of protein and minerals). The maximum yield and the best quality of alfalfa in Serbia can be obtained by cutting four or five times per year. In alfalfa stands, use of cutting system with three cuts per year is inefficient and does not allow full exploitation of cultivar genetic potential and environmental conditions. It is possible, and economically beneficial to grow alfalfa on pseudoglay soils after application of lime and organic manure, with recommended rates 2.5 t ha-1 lime and 30 t ha-1 manure. Cutting alfalfa at the beginning of flowering stage (5 cuts per year) provides hay with better quality - higher content of crude protein and lower portion of fibre fractions (neutral detergent fibre, acid detergent fibre, acid detergent lignin), and there is no reduction in dry matter yield. There is no differences in alfalfa quality after application of lower (2.5 t ha-1) and higher dose (5.0 t ha-1) of lime + 30 t ha-1 of organic manure, but there is significant increase of dry matter yield and protein yield per hectare followed by higher level of metabolic energy per unit area. Upon the results of this study, base of successful alfalfa production would be to develop management system and cultivars for different environments that would maximize hay yields without significant loses of quality.

Screening of Purslane (Portulaca oleraceaL.) Accessions for High Salt Tolerance

Purslane (Portulaca oleracea L.) is an herbaceous leafy vegetable crop, comparatively more salt-tolerant than any other vegetables with high antioxidants, minerals, and vitamins. Salt-tolerant crop variety development is of importance due to inadequate cultivable land and escalating salinity together with population pressure. In this view a total of 25 purslane accessions were initially selected from 45 collected purslane accessions based on better growth performance and subjected to 5 different salinity levels, that is, 0.0, 10.0, 20.0, 30.0, and 40.0 dS m−1 NaCl. Plant height, number of leaves, number of flowers, and dry matter contents in salt treated purslane accessions were significantly reduced (P ≤ 0.05) and the enormity of reduction increased with increasing salinity stress. Based on dry matter yield reduction, among all 25 purslane accessions 2 accessions were graded as tolerant (Ac7 and Ac9), 6 accessions were moderately tolerant (Ac3, Ac5, Ac6, Ac10, Ac11, and Ac12), 5 accessions were moderately susceptible (Ac1, Ac2, Ac4, Ac8, and Ac13), and the remaining 12 accessions were susceptible to salinity stress and discarded from further study. The selected 13 purslane accessions could assist in the identification of superior genes for salt tolerance in purslane for improving its productivity and sustainable agricultural production.

Physiological Response of Okra to Flea Beetle Herbivory as Measured by Leaf Loss, Chlorophyll Disruption, and Dry Matter Yield

Okra, Abelmoschus esculentus (L.) Moench, is attacked by the adult chrysomelid flea beetles, Podagrica spp. Information on physiological disruptions that occur due to flea beetle infestation affecting okra yield loss is incomplete. Screenhouse and field experiments were established to examine the effects of insect populations on leaf abscission, chlorophyll concentration, and biomass partitioning. Okra plants were grown in wire mesh screen cages and artificially infested with flea beetles, P. uniforma Jac., at population densities of 0, 5, 10, 20, 30, and 40 pairs per plant at 3 weeks after sowing (1 pair = 1 male and 1 female). In both experiments, okra plants had increased leaf abscission up to 100% at the 40-pair level in response to P. uniforma–induced injury. There were no significant differences in chlorophyll concentrations of plants at 0-, 5-, and 10-pair levels of infestation, suggesting the use of a compensatory mechanism by plants; at the 20-pair level a significant reduction occurred. Number of leaves per plant, shoots, roots, and dry fruit and total dry matter yield were reduced with infestation above the 20-pair level. More biomass was partitioned into roots at the 5- and 10-pair levels, but insect damage at populations beyond these levels completely suppressed the plant's ability to partition biomass. Dry fruit yields were reduced more than 50% when beetle populations increased beyond 20 pairs in both experiments. There was a correlation between insect density and number of leaves per plant and shoot, root, dry fruit, and total dry matter yield. The reduction in okra leaf production and chlorophyll content and increase in leaf abscission as a result of flea beetle infestation apparently resulted in a reduction in dry matter yield. The 20-pair level appeared to be the damage threshold of the insects. Physiological disruptions induced by the flea beetle at this level overcame the plants' ability to compensate for damage and caused significant reductions in leaf production, chlorophyll content, and dry matter yield and an increase in leaf abscission.

Impact of Simulated Airborne Soot on Maize Growth and Development

Various effects of the dry deposition of soot on maize were investigated in Keszthely (Hungary) in two consecutive years. In order to be able to study a wider range of weather conditions, some of the plants were placed in a Thornthwaite-Matter type evapotranspirometer and given ad libitum water supplies. Pollution with airborne black carbon was simulated throughout the season by distributing rates of 3 g?m–2 a week using a motorised dust sprayer. Among the plant growth parameters, the leaf area index was increased by 3% - 14%, depending on the year, suggesting that the plants were able to absorb the carbon settling on the leaves. The black carbon reduced the albedo of the canopy by 17.5% - 21.8%, depending on the year, forcing the polluted maize to absorb more energy. Part of this surplus energy was utilised for increased evapotranspiration (3.9% and 11% in the two years) and to raise the surface temperature of the canopy by 1℃ - 2℃ during the mid-day hours. The effect of the contamination on maize was more intense in the hot, dry year. The unfavourable effect of soot on maize fertilisation could be observed as a significant increase in the number of deformed ears, leading to a reduction in grain dry matter. The reduction in dry matter yield for polluted maize grown with irrigation in the evapotranspirometer was far less severe than that on non-irrigated plots, suggesting that irrigation was the most obvious solution for mitigating the negative effects of contamination with airborne soot.

English

The response of twelve rice varieties against six salinity levels (0, 4, 8, 12, 16 and 20 dS m-1) were studied at germination and early seedling stages. Data were analyzed using SAS and means were separated by LSD for final germination percentage (FGP), speed of germination (SG), germination energy percentage (GE%), plumule and radical length and plumule and radical dry weight. Based on dry matter yield reduction, rice varieties were classified as tolerant (T), moderately tolerant (MT), moderately susceptible (MS) or susceptible (S). Germination was completely arrested at 20 dS m-1 salt concentration. Salinity decreased FGP, SG, GE % and led to reduction in shoot and root length and dry weight in all varieties and the magnitude of reduction increased with increasing salinity stress. Rice varieties MR211, IR20, BR40 and MR232 showed greater salt tolerance during germination (germinated at 12 dS m-1 salinity). However, MR211, MR232 and IR20 performed better based on dry matter yield reduction. The result suggested that MR211, MR232 and IR20 might be used for further study of salinity effect on growth processes and physiological consequences at advanced stage of growth, since salt tolerance of a crop at germination and early seedling stage may not correspond to that at advanced stage.   Key words: Germination, seedling, rice, salinity stress, NaCl.