Responses of young cucumber plants to a diurnal temperature drop at different times of day and night

In greenhouse production of a number of vegetable and ornamental plant species, a short diurnal temperature drop in the end of the night or in the morning is commonly used to reduce stem elongation as an alternative to chemical growth retardants. Experiments were carried out to quantify the effects of a temperature drop at different times of the day and night on growth and photosynthetic activity of young cucumber plants. During 6 days plants were exposed daily to a temperature of 10 °C for 2 h at the beginning, in the middle and at the end of the night and day periods. The results have shown that plant response to drop may be qualitatively different in the light and darkness. While strongest effects of drop are observed when it is given in the daytime, for practical application in greenhouses it is more appropriate to reduce temperature at night. However, it may not be strictly necessary for cucumber seedlings to apply drop at the end of the night as it was stated in the literature. Thus, our results may cast doubt on the following statements: (a) temperature drops are not effective when delivered at other times of the day or night (except before sunrise), (b) optimal time for drop effects depends on the daily dynamics of stem and petiole elongation rate. It is rather drop itself is capable of modifying the dynamics of plant growth in the daily cycle.</p

Suelos de humedal del lago de Pátzcuaro, Michoacán, México

En México, en particular en el estado de Michoacán, el estudio sobre la génesis, morfología y función de los suelos hidromórficos no ha sido explorado de forma suficiente, pese a contar con grandes extensiones de humedales continentales, como la zona vadosa del lago de Pátzcuaro. Se estudiaron dos humedales representativos de la costa del lago de Pátzcuaro, Michoacán: uno de ellos saturado permanentemente, con desarrollo de gleysoles, y un humedal con inundación periódica, fluvisoles, desarrollados en una gran planicie aluvial. Los resultados indican la presencia de un gleysol háplico (colúvico, éutrico) (WRB, 2006), de coloración pardo oscuro, con cantidades moderadas de carbono orgánico (0.87% promedio), arcilloso > 30%, de estructura predominante de poliedros subangulares y prismas con segregación de sesquióxidos ferromanganosos, sobresaliendo los hiporrevestimientos de óxidos de fierro, y presencia de restos de ostrácodos en la mayor parte del perfil. Destaca una discontinuidad litológica. Por su parte, en el humedal aluvial se presenta un fluvisol háplico (hiperhúmico, éutrico) (WRB, 2006), un suelo con matriz de color pardo grisáceo, con altos contenidos de materia orgánica en todo el perfil (> 7 %) y restos de ostrácodos. Son suelos con alta saturación de bases (> 50 %). Tres zonas de humedad son bien definidas al interior de los suelos: una zona baja de endosaturación permanente, una zona intermedia producto de la capilaridad, y una zona de secado-humedecimiento alternado en los epipedone

Photosynthetic Nutrient and Water Use Efficiency of Cucumis sativus under Contrasting Soil Nutrient and Lignosulfonate Levels

To reduce the use of commercial conventional inorganic fertilizers, the possibility of using pulp and paper industry wastes in agriculture as an alternative source of nutrients is recently under study and discussion. This work aimed to evaluate the effect of sodium lignosulfonate application to soil on photosynthetic leaf nutrient (N, P, K, Ca, Mg, Fe, Mn, and Na) and water use efficiency. A pot culture experiment was conducted with cucumber seedlings, using five lignosulfonate concentrations (0, 1, 2.5, 5, and 10 vol. %) in sandy soil under sufficient or low nutrient availability for plants. The impact of nutrient availability on the plants’ physiological traits was stronger than the lignosulfonate impact. Under sufficient nutrient availability, the lignosulfonate application resulted in decreased photosynthetic N, P, K, Ca, Mg, Fe, and Na use efficiency. Cucumber growth and development, and photosynthetic nutrient, water, and light use efficiency were significantly reduced with a nutrient deficiency. The sodium lignosulfonate application was not successful in eliminating the negative effects of nutrient deficit on cucumber seedlings

Effect of Shungite Application on the Temperature Sensitivity of Allium cepa Respiration under Two Soil Water Regimes

This study aimed to evaluate whether shungite application to Umbric Podzols may affect leaf and root mitochondrial respiratory pathways, and the leaf response to a temperature change. A pot culture experiment was conducted with Allium cepa L. seedlings, using soil shungite concentrations of 0, 5, 10, and 20 g kg&minus;1 and two soil water regimes: well-watered (WW) and drying&ndash;wetting (DW) cycles. The soil water deficit increased the total respiration (Vt) of onion leaves, but not roots, under low (13 &deg;C) and high (33 &deg;C) measurement temperatures. Shungite application affected leaf Vt only at 13 &deg;C: it increased the Vt rate under WW and decreased itunder DW. An increase in the measurement temperature to 33 &deg;C enhanced the sensitivity of leaf respiration to the inhibitor of the alternative respiratory pathway (salicylhydroxamic acid, SHAM). Shungite application increased the contribution of theSHAM-sensitive pathway to the leaf Vt rate under WW, but not under the DW regime, regardless of the leaf temperature. In contrast to theSHAM-resistant pathway, the temperature sensitivity of the SHAM-sensitive rate decreased following the decrease in soil water availability. Shungite application increased the temperature sensitivity of both SHAM-sensitive and SHAM-resistant pathways under DW, and significantly decreased these parameters under WW. In summary, the decrease of temperature sensitivity of the alternative SHAM-sensitive respiratory pathway with a decrease of soil water availability or the shungite-related decrease of both SHAM-sensitive and SHAM-resistant leaf respiration may play an important role in enhancing the resistance of plant respiration to stress temperature

Physiological Responses of Lettuce (Lactuca sativa L.) to Soil Contamination with Pb

Contamination of agricultural soils with heavy metal leads to a decrease in the crop quality and yield, as well as increases in public health risks. In this study, we aimed to evaluate the impact of soil contamination with lead (Pb) on the growth, photosynthesis, respiration, and coupling between these physiological processes, as well as temporal dynamics of Pb uptake and accumulation by lettuce (Lactuca sativa L.) plants. For this 46-day pot experiment, Pb(NO3)2 was mixed with loamy Retisol soil with the rate of 0, 50, and 250 mg kg&minus;1. No significant differences in plant biomass accumulation were found between plants grown on Pb-free and Pb-rich soil, but root-weight ratio, root-to-shoot weight ratio, and leaf area were lower, and the number of leaves and leaf weight per unit area were significantly higher in plants grown on soil contaminated with Pb than in their counterparts grown on Pb-free soil. The concentration of Pb in plant root and shoot followed the increase in soil Pb, with Pb content in the roots being higher than in the shoots. Soil Pb decreased chlorophyll content, net CO2 assimilation rate and photosynthetic light use efficiency, but caused an increase in the leaf respiration rate regardless of whether respiration was performed in the light or in darkness. Increased ratio of respiration to photosynthesis reflects the shift in the carbon balance of lettuce plants toward carbon losses under stress conditions of soil contamination with Pb

Physical Properties of <i>Retisol</i> under Secondary Pulp and Paper Sludge Application

A positive effect of pulp and paper mill sludges as a rich source of organic substrates on soil properties was previously found for some types of sludge and soil. In this study, the effect of secondary pulp and paper sludge on water characteristics and thermal properties of Retisol, as well as the growth parameters of lettuce (Lactuca sativa L.), was tested on the basis of a pot experiment when watering plants with a 20 or 40% sludge solution. The sludge application enhanced plant growth with an increase in biomass accumulation of 21 and 53%, respectively, for 20 and 40% sludge treatments. When the sludge dose was increased from 0 to 40%, the number of leaves increased by 25%, and the leaf mass per area value increased by 42%. Due to the accumulation of more biomass in the shoots than in the roots, sludge causes a change in the allocation of plant biomass. A significant effect of the sludge application on soil particle and microaggregate sized compositions, as well as on the saturated soil hydraulic conductivity, was not found in this study. However, fitted soil water retention curves showed an increased soil water content in sludge-treated soil at all water content values exceeding field capacity. Secondary sludge application led to an increase in the saturated water content from 0.50 to 0.56 cm3 cm−3. The 40% sludge solution increased soil thermal conductivity from 0.92 to 0.98 W m−1 K−1 under saturated water content and from 0.83 to 0.92 W m−1 K−1 under field capacity. The thermal conductivity was higher in the sludge-treated than untreated soil due to a more pronounced positive effect of increased saturated water content than the negative effect of the increased organic matter content on heat transfer. The positive impact of secondary sludge application on both plant growth parameters and physical properties of Retisol, such as increased soil water-holding capacity and thermal conductivity coefficient confirms the possibility of using it to improve soil characteristics and plant productivity

Nutrient and Water Use Efficiency at Leaf Level of Cucumber Plants under Contrasting Soil Nutrient and Lignosulfonate Level

To reduce the use of commercial conventional inorganic fertilizers, the possibility of using pulp and paper industry wastes in agriculture as an alternative source of nutrients has recently been under study and discussion. This work aimed to evaluate the effect of sodium lignosulfonate application to soil on photosynthetic leaf nutrient (N, P, K, Ca, Mg, Fe, and Mn) and water use efficiency. A pot culture experiment was conducted with cucumber seedlings using five lignosulfonate concentrations (0, 1, 2.5, 5, and 10 vol. %) in sandy soil under sufficient or low nutrient availability for plants. The impact of nutrient availability on plant physiological traits was stronger than the lignosulfonate impact. Under the condition of sufficient nutrient availability, the lignosulfonate application decreased N, P, K, Ca, Mg, and Fe use efficiency, increased Mn use efficiency, and did not change water use efficiency. The decrease in nutrient use efficiency was connected with both photosynthetic rate decrease and leaf nutrient content increase. The decline in soil nutrient availability caused a decrease in nutrient and water use efficiency. Under low nutrient availability, soil lignosulfonate tended to increase nutrient and water use efficiency, but it was not successful in eliminating the negative effects of soil nutrient deficiency on plant growth, photosynthetic processes, and efficiency of nutrient use

Sodium Lignosulfonate Effect on Physiological Traits of Cucumis sativus L. Seedlings

The application of pulp and paper mill sludge to agricultural soils is commonly considered as a strategy to improve soil properties, promote plant growth, and reduce the demand for costly chemical fertilization. The aim of this study was to evaluate if sodium lignosulfonate (sLS), one of the sludges of pulp production, may affect the biomass production, the respiration (R) and net CO2 assimilation rate (An) at the leaf level, and the content and accumulation of trace elements in the leaves of cucumbers grown under a sufficient nutrient supply or soil nutrient deficit. A pot culture experiment was conducted using sLS application rates of 0, 1.0, 2.5, 5.0, and 10 vol% to sandy loam soil. The decline in nutrient availability caused an increase in the R/An ratio and dramatically depressed biomass accumulation. The leaf Fe, Ni, Cr, Co, Al, and Pb contents were lower under low nutrient availability than under sufficient nutrient supply. Although sLS was not very effective in lessening the negative effect of nutrient deficiency on biomass accumulation, it reduced respiratory carbon losses and cell membrane permeability in the leaves of cucumbers grown under nutrient deficit. The reduction in the toxic level of leaf Mn in seedlings grown under sufficient nutrient availability and the toxic level of leaf Fe under a nutrient deficit might also be considered as a positive effect of the sLS application to sandy soil

Sodium Lignosulfonate Effect on Physiological Traits of <i>Cucumis sativus</i> L. Seedlings

The application of pulp and paper mill sludge to agricultural soils is commonly considered as a strategy to improve soil properties, promote plant growth, and reduce the demand for costly chemical fertilization. The aim of this study was to evaluate if sodium lignosulfonate (sLS), one of the sludges of pulp production, may affect the biomass production, the respiration (R) and net CO2 assimilation rate (An) at the leaf level, and the content and accumulation of trace elements in the leaves of cucumbers grown under a sufficient nutrient supply or soil nutrient deficit. A pot culture experiment was conducted using sLS application rates of 0, 1.0, 2.5, 5.0, and 10 vol% to sandy loam soil. The decline in nutrient availability caused an increase in the R/An ratio and dramatically depressed biomass accumulation. The leaf Fe, Ni, Cr, Co, Al, and Pb contents were lower under low nutrient availability than under sufficient nutrient supply. Although sLS was not very effective in lessening the negative effect of nutrient deficiency on biomass accumulation, it reduced respiratory carbon losses and cell membrane permeability in the leaves of cucumbers grown under nutrient deficit. The reduction in the toxic level of leaf Mn in seedlings grown under sufficient nutrient availability and the toxic level of leaf Fe under a nutrient deficit might also be considered as a positive effect of the sLS application to sandy soil