SILICON NUTRITION AND PHYTOPHTHORA DRECHSLERI INFECTION EFFECTS ON GROWTH AND MINERAL NUTRIENTS CONCENTRATION,UPTAKE, AND RELATIVE TRANSLOCATION IN HYDROPONIC-GROWN CUCUMBER

A hydroponic experiment was performed to investigate silicon (Si) and Phytophthora drechsleri root rot effects on growth and tissue partitioning of Si, zinc (Zn), iron (Fe), and manganese (Mn) in two cucumber cultivars (Cucumis sativus L. cvs. ‘Dominus’ and ‘Super Dominus’). Root length, plant height, and root fresh weight were significantly decreased by P. drechsleri, which were all significantly alleviated by 1.0 mM Si. Increasing Si level in the nutrient solution was accompanied with its enhanced uptake by cucumbers. Plants infected with P. drechsleri transported lower Mn to shoot than non-infected plants. Influence of P. drechsleri infection on root Fe concentration was dependent on cucumber cultivar while a decrease in root Zn concentration was found in infected cucumbers. Silicon nutrition increased Zn and Fe uptake in both cucumber cultivars. It is suggested that Si nutrition improved the crop growth, particularly under biotic stress, and hereby, increased micronutrients uptake by cucumber.     

DIFFERENTIAL RESPONSE OF TWO OLIVE CULTIVARS TO EXCESS MANGANESE

The response of three-month-old rooted cuttings of the olive cultivars ‘Picual’ and ‘Koroneiki’ grown in black plastic bags containing perlite as a substrate to excess manganese (Mn) (640 μM) was studied. The rooted cuttings were irrigated with 50% modified Hoagland nutrient solution. At the end of the experimental period, which lasted 130 days, the total fresh and dry weights, as well as the shoot elongation of ‘Picual’ plants were significantly reduced under excess Mn (640 μM), compared to the control plants (2 μM), whereas the growth of ‘Koroneiki’ plants was similar in both Mn treatments. The tolerance index, which is derived from the ratios between the plant growth data of different treatments and the control one, of ‘Picual’ plants to excess Mn was about half of this of ‘Koroneiki’ plants. In both cultivars, the concentrations of Mn in various plant parts (root, basal stem, top stem, basal leaves, top leaves) were significantly increased as Mn concentration in the nutrient solution increased. Furthermore, in the 640 μM Mn treatment, 2 to 2.5-fold greater Mn concentrations were recorded in almost all plant parts of ‘Koroneiki’, than those of ‘Picual’. Similar results were recorded with regard to the total Mn content per plant (‘Koroneiki’ absorbed much more Mn from the nutrient solution than ‘Picual’). On the other hand, excess Mn negatively affected the absorption of iron (Fe), calcium (Ca), magnesium (Mg), phosphorus (P), zinc (Zn), and boron (B), depending on the olive cultivar. In both cultivars, while the Mn use efficiency was significantly decreased under excess Mn conditions, the nutrient use efficiencies of P, Ca, and Fe were significantly increased, compared to the control plants (2 μM Mn). It was also found that excess Mn resulted in a significant increase of stomatal conductance and transpiration rate of both cultivars, whereas the photosynthetic rate was significantly increased only in ‘Koroneiki’. In ‘Picual’, similar photosynthetic rates were recorded in both Mn treatments. The measurement of the various chlorophyll fluorescence parameters, F_v/F_m and F_v/F₀ ratios, revealed that the functional integrity of photosystem II (PSII) of photosynthesis was not affected due to excess Mn, irrespectively of the cultivar. In conclusion, although ‘Koroneiki’ tissues had much higher Mn concentrations than those of ‘Picual’, the parameters related to the growth and photosynthetic performance of plants indicates that the internal tolerance of ‘Koroneiki’ tissues to excess Mn was higher than this of ‘Picual’.     

COMPARATIVE STUDIES ON THE IRON AND ZINC CONTENTS ESTIMATION USING ATOMIC ABSORPTION SPECTROPHOTOMETER AND GRAIN STAINING TECHNIQUES (PRUSSIAN BLUE AND DTZ) IN MAIZE GERMPLASMS

Malnutrition arising from dietary deficiency of critically important mineral micronutrients such as iron (Fe) and zinc (Zn) is a serious problem affecting nearly half of the world's population. Screening for micronutrients rich breeding lines includes the estimation of grain micronutrient contents in the seed samples using atomic absorption spectrophotometer (AAS). Though the protocol produces precise results, it is usually costly and time consuming. The nutritionist started searching for newer methods like staining the particular plant tissue with dyes so the initial screening of among vast germplasm lines becomes easier. A set of four hundred and thirty genotypes were used in this experiment wherein the reliability and the cost effectiveness of the use of the staining method in place of the estimation using AAS was investigated. The intensity of the color developed was directly proportional to the amount of iron and zinc in the grains and were scored as 1, 2, 3, 4, and 5. The genotype ‘UBC 7’ has got the maximum level of iron (65.43 mg kg^?1) with about 64 lines is found to contain higher levels of iron. The genotype ‘UMI 421’ had the maximum level of zinc (60.15 mg kg^?1) along with ten lines showing richer zinc levels. The genotypes namely ‘UMI 1069’, ‘UMI 630’, ‘UMI 473’, ‘UMI 327’, and ‘UMI 382’ are found to be having considerably higher levels of iron and zinc in the kernels. These lines may be used for the introgression of the traits concerning micronutrient enhancement into the popular elite cultivars. When compared to the estimation with AAS, the staining methods with Prussian Blue and Dithizone (DTZ: 1,5-diphenyl thiocarbazone) are found be very cost effective and precise in identifying and categorizing the lines as micronutrient rich/deficit. The varying color intensities serve as a reliable selection criterion for grain micronutrient contents in maize and other cereal crops. These protocols, could, therefore, be effectively used as the initial screening methodology and so the genotypes might be identified for higher grain micronutrient contents among huge population in a short period of time.     

Effect of Two Nitrogen Forms on the Growth and Iron Nutrition of Pea Cultivated in Presence of Bicarbonate

ABSTRACT

Two cultivars of pea: ‘PS210713’ (‘PS’), sensitive to iron deficiency, and ‘Marveille de Kelvedon’ (‘MK’), tolerant, were cultivated in controlled climatic conditions during one month, on a nutrient solution containing either nitrate (NO₃ ^?, 4 mM) or ammonium (NH₄ ⁺, 4 mM) and in the presence of bicarbonate (10 mM). The effects of these nitrogen forms on the growth and the mineral nutrition, and especially iron nutrition are analyzed.

The reduction of growth by bicarbonate was approximately 30% in case of NO₃ ^? nutrition in the two cultivars, whereas in ammoniacal treatment the reduction is only 6% and 18% respectively in ‘PS’ and ‘MK’ cultivars.

In presence of bicarbonate, the plant growth is not stimulated by NO₃ ^?relatively to its growth on ammoniacal medium, as often noticed when plants are cultivated on medium without bicarbonate: In presence of this compound, the biomass production of plant pea, was not influenced by the nitrogen forms. The nitric source led to a ferric chlorosis in the sensitive cultivar plants whereas any chlorosis was noted when ammoniacal source was applied. On the other hand, nitric nitrogen form decreased the nitrogen feeding of plants and increased the potassium one, while the effect of the ammoniacal nitrogen form on these nutrients was quite the inverse. In addition, the later increased the allocation of iron towards shoots. Besides, with this nitrogen source there was not accumulation of nitrate in the plant tissues. In nitric feeding case, the nitrate is mainly accumulated in the roots of the two cultivars. It is noticeable that the sensitive cultivar (‘PS’) accumulates three times more nitrate than the tolerant one (‘MK’).

On the level of the whole plant, the iron and phosphorus nutrition seems unaltered by the nitrogen form.     

VARIATION IN PHOSPHORUS EFFICIENCY AMONG BRASSICA CULTIVARS I: INTERNAL UTILIZATION AND PHOSPHORUS REMOBILIZATION

Plants have adapted a number of mechanisms to cope with widespread phosphorus (P) deficiency in arable lands. Crop species and even cultivars differ widely in one or more of these adaptive mechanisms hence, in P efficiency. Identification of these mechanisms is pre-requisite for long term breeding programs. Two independent experiments were conducted to study the possible mechanisms of P efficiency in Brassica cultivars. Eight Brassica cultivars (‘B.S.A.’, ‘Toria’, ‘Toria Selection’, ‘Brown Raya’, ‘Peela Raya’, ‘Dunkeld’, ‘Rainbow’, and ‘CON-1’) were selected on the basis of differences in growth under P deficiency from preliminary experiment. In the first experiment, cultivars were grown for 40 days in sand supplied either with sparingly soluble phosphate rock (PR) or soluble mono-ammonium phosphate (MAP). Cultivars differed significantly (P<0.05) for biomass production, P contents and P use efficiency. Low P availability in PR treatment resulted in significantly lower dry weights and P contents than those grown with MAP. The cultivars ‘Rainbow’, ‘Brown Raya’ and ‘Dunkeld’ accumulated more biomass (3.2 g/pot) and P contents (3.0 mg/pot) than other cultivars when grown with PR. Root dry weight was significantly correlated with shoot dry weight, shoot P content and total P content (r > 0.65) indicating significance of improved root growth for P acquisition. While in the second experiment cultivars were grown with adequate P for 30 days and then P was withdrawn from the nutrient solution by replacing fresh P free nutrient solution for 10 days. Induced P deficiency increased P contents in young leaves by two folds indicating remobilization of P from older leaves and shoot. Nonetheless cultivars varied for remobilization but differences in P remobilization could not explain the differences in P utilization efficiency among cultivars. Hence further experimentation to study root morphology, P uptake, and organic acid exudation by these cultivars in relation to P deficiency is recommended.     

The Symbiotic Performance and Plant Nutrient Uptake of Certain Nationally Registered Chickpea (Cicer Arietinum L.) Cultivars of Turkey

An experiment was conducted under greenhouse conditions to test the symbiotic performance and plant nutrient uptake of the twelve nationally registered chickpea cultivars (‘Çak?r’, ‘I??k-05’, ‘Can?tez-87’, ‘Hisar’, ‘Ya?a-05’, ‘Azkan’, ‘Küsmen-99’, ‘Gökçe’, ‘Damla-89’, ‘Diyar-95’, ‘Aziziye-94’, and ‘?zmir-92’) in Turkey. Inoculation with Mesorhizobium ciceri increased the average nodule number by 687%, nodule weight by 257%, plant height by 6%, shoot dry weight by 12%, root dry weight by 21%, chlorophyll content by 4.2%, nitogen (N)% by 7.9%, and total N by 22.7%. Averaged across chickpea cultivars, inoculation also significantly increased sulfur (S) by 14.4%, phosphorus (P) by 1.9%, magnesium (Mg) by 13.8%, potassium (K) by 6.2%, calcium (Ca) by 17.4%, copper (Cu) by 4.5%, iron (Fe) by 16.5%, manganese (Mn) by 10.9% and zinc (Zn) uptake by 9.4%. The macro- and micronutrient uptake of cultivars significantly correlated with their nitrogen content and the magnitude of response to inoculation in relation to nodulation, plant growth, nitrogen fixation, and nutrient uptake significantly varied among cultivars. Based on the amount of fixed N and plant nutrient uptake, ‘Azkan’, ‘Aziziye-94’, ‘Küsmen-99’, ‘Diyar-95’, and ‘Hisar’ were the genotypes with the most positive response to inoculation. Our data showed that nodulation, nitrogen fixation, plant dry matter production, and macro- and micronutrient uptake of the inoculated chickpea can be improved by selecting the best compatible cultivar.     

Phytosiderophore release in relation to multiple micronutrient metal deficiency in wheat

Phytosiderophore (PS) release, which occurs mainly under iron deficiencies in the representative Poaceae, has been speculated to be a general adaptive response to enhance the acquisition of micronutrient metals. However, it is very common to encounter deficiency of micronutrients other than iron (Fe) in soils and interactions with respect of multi-micronutrient deficiency to effect on PS release are not known. Further, the diurnal rhythm for the release of PS may also be affected under multiple micronutrient deficiency. PS release capacity and PS content of roots and the diurnal rhythm of PS release was measured in selected efficient and inefficient wheat genotypes varied on individual and combined deficiency of Fe, zinc (Zn), copper (Cu) and manganese (Mn) in nutrient solution culture. A nutrient sufficient treatment was also taken as experimental control. Lack of Fe in the nutrient medium caused a significantly higher release of PSs followed by Zn, Mn and Cu in the same order. The diurnal rhythm of PS release was similar in the absence of either of the micronutrients or under their combined deficiency. Micronutrient sufficient control did not release any PS. Fe-use-efficient cultivars produced and released a larger amount of PS and differed from the inefficient cultivars in terms of the PS release but not in the PS biosynthesis in the roots. Thus, indicating that the limitation at the level of release of the PS is responsible for low Fe use efficiency of the Fe deficiency susceptible cultivars. Further, the diurnal variation in the PS release was similar for all the investigated wheat cultivars and did not influence the variation in the Fe use efficiency.     

GENOTYPIC VARIATIONS IN POTASSIUM UPTAKE AND UTILIZATION IN COTTON

Genotypic differences in potassium (K) uptake and utilization were compared for eight cotton cultivars in growth chamber and field experiments. Four of the cultivars (‘SGK3’, ‘SCRC18’, ‘SCRC21’ and ‘SCRC22’) typically produce lower dry mass and the other four (‘Nannong8’, ‘Xiangza2’, ‘Xinluzao12’ and ‘Xiangza3’) produce greater dry mass in K-deficient solution (0.02 mM). The mean dry weight of seedlings (five-leaf stage) of cultivars with greater biomass was 155% higher than that of cultivars with lower biomass yield under K deficiency. However, all the genotypes had similar dry matter yields in K-sufficient solution (2.5 mM). Thus, the four cultivars with superior biomass yield under low K medium may be described as K efficient cultivars while the inferior cultivars may be described as K inefficient. Although seeds of the studied cultivars originated from different research institutes or seed companies, there were little differences in seed K content among them, irrespective of their K efficiency. Consequently, there were no significant differences in K accumulation in seedlings (4 d after germination in a K-free sand medium) just before transferring to nutrient solutions. However, the K efficient genotypes, on average, accumulated twice as much K at 21 d after transferring to K-deficient solution (0.02 mM). A much larger root system as well as a slightly higher uptake rate (K uptake per unit of root dry weight) may have contributed to the higher net K uptake by the K efficient cultivars. In addition, the K efficiency ratio (dry mass produced per unit of K accumulated) and K utilization efficiency (dry mass produced per unit of K concentration) of the K efficient cultivars exceeded those of the K inefficient genotypes by 29% and 234%, respectively, under K deficiency. On average, the K efficient cultivars produced 59% more potential economic yield (dry weight of all reproductive organs) under field conditions even with available soil K at obviously deficient level (60 mg kg^?1). We noted especially that the four K inefficient cultivars studied were all transgenic insect-resistant cotton, suggesting that the introduction of foreign genes (Bt and CpTI) may affect the K use efficiency of cotton.     

VARIATION IN PHOSPHORUS EFFICIENCY AMONG BRASSICA CULTIVARS II: CHANGES IN ROOT MORPHOLOGY AND CARBOXYLATE EXUDATION

Increased phosphorus (P) efficiency is needed to sustain agriculture productivity on soils with low available P. Significant differences were found among Brassica cultivars for growth, P utilization, and remobilization under P deficiency (see our companion paper, Aziz et al., 2011a). To identify the possible mechanisms of P acquisition from low soluble P compounds, four cultivars (‘Rainbow’, ‘CON-1’, ‘Dunkeld’, and ‘Peela Raya’) were selected to ascertain the relationship of their differential P acquisition and growth with their root length in soil and with organic acid release pattern in solution culture experiments. For this purpose their growth and P acquisition from phosphate rock (PR) was compared with calcium di-hydrogen phosphate (Ca-P) when adding uniform dose of 100 mg P kg^?1 soil separately from the two sources. Biomass accumulation, root length, root fineness, plant P uptake and ash alkalinity was significantly (P < 0.01) different in plants of all the four cultivars when supplied with PR or Ca-P in soil. Minimum biomass produced by ‘Peela Raya’ grown with either P source was followed by ‘CON-1’, ‘Dunkeld’, and ‘Rainbow’ in ascending order. Shoot dry matter production had a significant positive correlation with root dry matter production (r = 0.85, P < 0.01), root length (r = 0.59, P < 0.05) and root P uptake (r = 0.95, P < 0.01). Cultivars varied significantly for organic acid secretion in solution culture experiment. Higher quantities of secreted citric acid, malic acid and tartaric acid in solution culture experiment were measured for ‘Rainbow’ and ‘Dunkeld’ cultivars. Efficient performance of these two cultivars for growth and P uptake was associated with their longer roots and more secretion of organic acids especially citric acid.     

Growth,yield and nutrient uptake of taro grown under upland conditions

There is a scarcity of basic information on dry matter accumulation by various plant organs, nutrient uptake, and yield of taro [Colocasia esculenta (L.) Schott] grown under upland conditions. These data are essential for the development of technological packages, growth simulation models, and decision support systems designed to promote agrotechnology transfer of the crop in the tropics. Two taro cultivars were planted and harvested for biomass about every six weeks during the growing season. At each harvest, plants were separated into various plant parts and their dry matter and nutrient content were determined. There were no significant differences (P<0.05) in total and edible dry matter content between cultivars. However, cultivar ‘Lila’ absorbed significantly smaller amounts of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and zinc (Zn) than cultivar ‘Blanca’, suggesting that it had a higher nutrient‐use efficiency. Fresh corm yields were not significantly different and averaged 20,221 kg/ha for both cultivars.     

Effect of salt stress on nitrogen fixation by different cultivars of green beans

Nitrogen fixation by three cultivars of green beans (Phaseolus vulgaris L., cv. ‘Tender Improved’, ‘Slim Green’, and ‘Kentucky Wonder') was investigated under normal (control = 0.3 bars osmotic pressure) and NaCl salinized (3.0 bars osmotic pressure) conditions. The study was carried out in a greenhouse with a sand culture technique, using a system which automatically recirculated a modified complete Hoagland nutrient solution with only 5 ppm N. Nitrogen was added as K¹⁵NO₃ to the culture solution. Plants were harvested three times (10, 20, and 30 days after the completion of the salt and N treatments). Plant parts (shoots and roots) were evaluated separately for dry matter production, total‐N concentration (%), total‐N content (mg/plant part), total‐N fixation (mg/plant part), and percentage of total‐N fixation. Salt stress significantly decreased dry matter production, total‐N content (uptake plus fixed), percent of total‐N fixed (based on the total‐N content of plant parts), and amount of total‐N fixed by plants. Among the three cultivars, Slim Green produced the lowest dry matter, fixed the least amount of N₂, and had the lowest fixed‐N percentage for any corresponding treatment, particularly under NaCl stress conditions.     

Influence of micronutrient and phoshorous levels and chelator to iron ratio on growth,chlorosis, and nutrition of Vaccinium ashei reade and V. elliottii chapman

‘Tifblue’ (V. ashei Reade) and US 280 (V. elliotti Chapman) blueberry plants were exposed to 2×2×2 factorial treatments of high and low phosphate and micronutrients (Cu, Zn, Mn, and B) and excess or stoichiometric concentrations of a chelator (EDDHA) added to Fe(NO₃)₃ in pH 6.8 solution cultures. Phosphorous was applied at 20 (low) or 400 (high) μM levels, micronutrients at low or high levels and either a 1:1 or 10:1 ratio of chelator to Fe concentrations.

Excess chelator in the nutrient solution always increased the severity of chlorosis except for US 280 plants grown under low P and stoichiometric chelator where neither micronutrient level resulted in chlorosis. Increased P concentration usually resulted in more severe chlorosis except for ‘Tifblue’ plants grown under low micronutrients and stoichiometric chelator where chlorosis did not develop with either P level. ‘Tifblue’ and US 280 differed in there response to excess solution Cu levels.

Unlike highbush blueberries (V. corymbosum L.), these two species of blueberries responsed to excess chelator in a manner similar to that reported for monocots.     

GENOTYPIC DIFFERENCES IN ROOT MORPHOLOGY AND PHOSPHORUS UPTAKE KINETICS IN BRASSICA NAPUS UNDER LOW PHOSPHORUS SUPPLY

Application of phosphorus (P) fertilizer is important in crop production because of the low bioavailability of phosphorus to plants in both acidic and calcareous soils. Although rapeseed (Brassica napus) is generally sensitive to P deficiency, different cultivars differ widely in this respect. Differences in P uptake and utilization between two rapeseed cultivars, one P-efficient (‘97081’) and one P-inefficient (‘97009’), were evaluated in solution culture by studying the changes in root morphology and parameters of P uptake kinetics in response to low-P stress. The P-efficient cultivar had lower Km and Cmin values and higher Vmax and developed longer and denser lateral root hair with greater number of root tips and branches under low-P stress, which resulted in a better developed root system and more efficient uptake of P. That, in turn, led to higher concentration and accumulation of P in the plants, culminating in higher biomass production. However, P utilization efficiency (biomass production per unit P accumulated in plant) of the P-efficient ‘97081’ was lower than that of ‘97009’ when P was deficient. These results suggest that P efficiency in rapeseed is due to a better developed root system as well as efficient uptake of P.     

Salt-Induced Stress Effects on Biomass,Photosynthetic Rate,and Reactive Oxygen Species-Scavenging Enzyme Accumulation in Common Bean

We studied the effects of salinity stress on biomass production, photosynthesis, water relations, and activity of antioxidant enzymes in two cultivars of common bean (‘HRS 516’ and ‘RO21’). Seedlings were raised in nutrient solution supplemented with increasing concentrations of sodium chloride (NaCl) at 0, 50, and 100 mM. After 10 days of salinity treatment, the plants were sampled to determine the enzyme activity, protein content and dry biomass. Plant biomass and activities of most antioxidant enzymes were adversely affected by salinity stress. Leaf osmotic potential was found to be directly proportional to salt stress. The cultivar, ‘HRS 516’ accumulated less sodium (Na⁺) than ‘RO21’. Under salinity, superoxide dismutase (SOD) enzyme activity increased 3 folds in both bean cultivars (‘HRS 516’ and ‘RO21’) compared to other antioxidants (APX, CAT, and GR). While not neglecting other possible factors, photosynthesis and biomass remains reliable indicators of plant functioning in response to salinity stress.     

EFFECT OF PETUNIA STOCK PLANT NUTRITIONAL STATUS ON FERTILIZER RESPONSE DURING PROPAGATION

Fertilization strategies during stock plant and cutting production are linked in terms of cutting nutrient levels and quality. Objectives were to evaluate (1) the effect of stock plant nutrition on tissue nutrient concentration and growth during vegetative propagation and (2) response to fertilizer during propagation for cuttings with 4 different initial tissue nutrient concentrations. ‘Supertunia Royal Velvet’ petunia stock plants were grown under constant fertigation of 0, 50, 100 or 200 mg nitrogen (N)^.L^?1 for 21 days. The 200 mg N^.L^?1 solution contained 150 nitrate (NO₃-N), 50 ammonium (NH₄-N), 24 phosphorus (P), 166 potassium (K), 40 calcium (Ca), 20 magnesium (Mg), 0.7 sulfur (S), 1.0 iron (Fe), 0.5 manganese (Mn), 0.5 zinc (Zn), 0.24 copper (Cu), 0.24 boron (B), and 0.1 molybdenum (Mo). Providing a complete fertilizer during propagation of petunia, beginning immediately after sticking of cuttings, reduces the risk of nutrient deficiency. Particularly in situations where fertilizer is not applied early during propagation, stock plants should be managed to ensure unrooted cuttings have adequate nutrient reserves.     

UPTAKE AND DISTRIBUTION OF SELENIUM,NITROGEN AND SULFUR IN THREE BARLEY CULTIVARS SUBJECTED TO SELENIUM APPLICATIONS

Selenium (Se) is an essential micronutrient for humans and animals, and also affects plant metabolism. In this study, the effects of increasing doses of Se application on the uptake of selenium (Se), nitrogen (N), and sulfur (S) content of three barley cultivars were investigated. The analysis indicated that the Se contents were highest in root tissues, intermediate in grain, and lowest in stem tissues in all cultivars. Total Se accumulations (whole plant) were highest in ‘Bülbül 89’ (0.171 mg kg^?1), intermediate in ‘Çetin 2000’ (0.153 mg kg^?1), and lowest in ‘Tarm 92’ cultivars (0.124 mg kg^?1). In all cultivars, the increase in grain Se content resulted in a decrease in the grain N content. While ‘Bülbül 89’ can be suggested for biofortification purposes, less Se accumulating ‘Tarm 92’ cultivar can be suggested as a fodder in Se contaminated or high Se containing areas.     

Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

Micro nutrient toxicity in French marigold

The influence of elevated levels of micronutrients on the growth and flowering of French marigold (Tagetes patula L.) was investigated. Plants were grown with nutrient solution containing 0.25, 0.5, 1, 2, 3, 4, 5, or 6 mM boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn) and toxicity development was monitored. The threshold micronutrient concentrations that induced visible foliar toxicity symptoms were 0.5 mM B, 4 mM Cu, 4 mM Fe, 2 mM Mn, 1 mM Mo, and 5 mM Zn. The dry matter yields during the 5 week experimental period were reduced when micronutrient concentrations exceeded 0.5 mM B, 3 mM Cu, 3 mM Fe, 6 mM Mn, 0.5 mM Mo, and 5 mM Zn in the fertilizer solution. Leaf chlorophyll contents decreased when the nutrient solution concentrations of Cu, Fe, and Mn were greater than 0.5 mM, 3 mM, and 2 mM, respectively. Visual toxicity symptoms of the six micronutrients were characterized.     

Effect of increasing potassium levels for alleviating sodium chloride stress on the growth and yield of tomato

Abstract

The efficacy of using various levels of potassium (K) (4, 8, and 16 mM) under saline conditions to alleviate the detrimental effects of salt‐stress were studied using five tomato (Lycopersicon esculentum Mill) cultivars, ‘Strain 19’, ‘Pearson’, ‘Montecarlo’, ‘Maruthuam’, and ‘Pusa Rub’. Results of the study revealed that 50 mM sodium chloride (NaCl) in a Hoagland nutrient solution significantly reduced stem height, fruit weight, and whole plant dry weights, but increased number of fruits/plant and improved fruit quality by increasing total soluble solids. It did not significantly affect leaf count, percent fruit set, or dry weight. The addition of 4, 8 and 16 mM potassium nitrate (KNO₃) to the nutrient solution containing 50 mM NaCl resulted in sodium/potassium (Na/K) ratios of 12.5, 6.3, and 3.1, respectively. The Na/K ratios of 12.5 and 6.3 produced significant improvement in stem height, percent fruit set, number of fruits/plant, fruit weight, and whole plant dry weight. The Na/K ratio of 3.1 was found to be detrimental as it resulted in sharp reduction of plant dry weight compared to the control. Percent total soluble solids was not significantly affected by the addition of any level of K to the saline nutrient solution. The performance of the tomatoplant grown under saline conditions supplemented with K in the nutrient solution indicated a higher response at the lowest K concentration used in this study.     

Physiological Disorder of Rice Associated with High Levels of Iron in Growth Medium

Three rice (Oryza sativa L.) varieties viz. ‘CR 683‘, ‘Budumoni’ “Budumoni”, and ‘Akisali’ were grown in sand culture in a greenhouse with three levels of iron (Fe) in nutrient solutions viz., 0.045 (control), 5.34, and 7.12 mM Fe to study the effects of iron on physiology of rice seedling growth. Shoot length, root, and shoot dry weights were reduced significantly by higher levels of Fe in the medium. Results of leaf bronzing have revealed higher bronzing score in the seedlings grown at 7.12 mM Fe in the growth medium. Occurrence of bronzing was severe in varieties ‘CR683’ and ‘Akisali’. Variety ‘Budumoni'maintained higher leaf chlorophyll content, nitrate reductase activity and total soluble protein in the leaves at 5.34 and 7.12 mM Fe. Higher concentration of iron in the nutrient medium exerted an inhibiting effect on the concentration and content of almost all the macro and micronutrients in the root and shoot. Higher Fe and nitrogen (N) contents and lower phosphorus (P), potassium (K), manganese (Mn), copper (Cu), and zinc (Zn) were determined in roots and shoots in plants grown in medium supplied with 7.12 mM Fe. The variety ‘Budumoni’ “Budumoni” performed relatively better in comparison to other tested varieties at 7.12 mM Fe in the growth medium. ‘Budumoni’ “Budumoni” can be considered a suitable rice variety to use in the rice-breeding programme for Fe toxicity tolerance in acid soils of Assam.