Effects of Dibutyl phthalate and phthalic acid on chlorosis recovery in iron‐deficiency stressed sorghum cultivars

The effects of DBP (Dibutyl phthalate) and PA (Phthalic acid) supplied to the nutrient medium of Fe‐deficiency stressed sorghum cultivars, CSH‐5, 2077‐A, and CS‐3541 were examined. It was found that both the chemicals (50 mg/1) caused recovery of the cultivars CSH‐5 and 2077‐A in 4 days of treatment. Furthermore, the growth of roots, especially the adventitious roots, was increased by the chemicals.     

Comparison of HCl extraction versos total iron analysis for iron tissue analysis

Extraction of Fe from fresh leaves with 0.1 N HCl proved to be a better indicator of the Fe status of a variety of ornamental tropical foliage and flowering plants compared to total Fe, 0.1 N HCl‐ether, and IN HCl extraction. It consistently gave higher correlations (r = 0.73 to 0.95 depending on the species) with chlorophyll concentration than the other methods tested. However, even 0.1 N HCl extraction did not distinguish levels of Fe deficiency accurately when compared between species.     

Comparative growth of two peach seedling rootstocks under alkaline soil conditions

An almond X peach seed line, ‘Titan’ X Nemaguard (T X NG), which is tolerant to lime‐induced chlorosis, was compared to a susceptible seedling rootstock, Nemared, under alkaline conditions. The tolerant rootstock's growth was not affected by Fe stress, whereas the susceptible rootstock showed chlorosis which corresponded to approximately a 20% chlorophyll loss in the new foliage during the 18‐week stress period, a 62% decrease in shoot dry weight and a 22% decrease in plant height.     

Metal micronutrients relationships in crop,soil, and common weeds of two maize (Zea mays L.) fields

Deficiencies of metal micronutrients are common in some calcareous soils. Samples of aerial parts of maize and five common weeds and also soil beneath these plants were collected and analyzed to investigate the status and relationships of metal micronutrients in soil, crop, and common weeds of maize field trials at two sites. Results showed that Fe concentration in five studied weeds was higher than that of maize; the highest Fe concentration was found in Convolvolus arvensis and Echinochloa crus-galli (first site) and in Convolvolus arvensis tissues (second site). At both sites, the highest Mn concentration was observed in aboveground parts of Echinochloa crus-galli. The concentration of Mn (both sites) and Fe and Cu (second site) were remarkably higher in Echinochloa crus-galli tissues in comparison with maize. Also the concentrations of Fe (both sites) and Cu (second site) were considerably higher in Convolvolus arvensis tissues in comparison with maize. Available Fe was the highest in the soil beneath Convolvolus arvensis and Portulaca oleracea (first site) and beneath Convolvolus arvensis and Cenopodium album (second site). The high value of available Fe in the soil beneath Convolvolus arvensis may explain why Fe concentration was the highest in aerial parts of this weed species.     

Co-situs application of controlled-release fertilizers to alleviate iron chlorosis of paddy rice grown in calcareous soil

Abstract

Co-situs is the placement with one application of a sufficient amount of controlled-release fertilizer for an entire growing season at any site, together with seeds or seedlings, without causing fertilizer salt injury. An experiment was conducted to find an efficient method for ameliorating Fe deficiency in two rice cultivars (cv. Tsukinohikari and cv. Sasanishiki) grown in a calcareous soil (pH 9.2, CaCO₃ 384 g kg^?1), which was poor in organic matter (0.1 g kg^?1) and available Fe (3.0 μg g^?1 soil). The field treatments consisted of co-situs application of the following fertilizers: 1) controlled-release NPK fertilizer (CRF-NPK) containing no micronutrients; 2) controlled-release NPK fertilizer containing micronutrients (CRF-M1); and 3) controlled-release NPK fertilizer containing micronutrients (CRF-M2). The main difference between CRF-M1 and CRF-M2 was that the former had larger granules than the latter. All the fertilizers were placed in contact with the roots of rice seedlings at transplanting time. Plants in the CRF-M1 and CRF-M2 treatments had similar lengths, number of stems, leaf age, and leaf color (SPAR value) during the cultivation period. By contrast, plants from the CRF-NPK treatments grew poorly, showed severe chlorosis symptoms of Fe deficiency, and all died on 30 DAT. Plants of both cultivars accumulated more macroand micronutrients with the CRF-M2 treatment than with the CRF-M1 treatment. The grain yield of cv. Tsukinohikari was 0.0, 1,910, and 2,160 kg ha^?1 for the CRF-NPK, CRF-M1, and CRF-M2 treatments, respectively, and 0.0, 2,490, and 2,860 kg ha^?1 for the same treatments for cv. Nihonbare. Chlorosis due to iron deficiency was successfully ameliorated and world-average grain yields were obtained with the co-sites application of both controlled-release fertilizers.     

Technologies for the diagnosis and remediation of Fe deficiency

The objective of this paper is to review the developments in the last few years in two important issues related to Fe deficiency in plants. First, the current knowledge on the possible ways to carry out the diagnosis and prognosis of Fe deficiency in plants is discussed. This includes discussion on the best ways to carry out a meaningful analysis of Fe-containing compounds in different plant parts. We will also discuss other measurement techniques that can permit to assess the Fe nutritional status in plants, including leaf chlorophyll concentrations and others. Second, the new developments in management techniques to control and remediate iron deficiency are discussed. This includes possible improved ways to supply Fe compounds available to plants, both to the soil and to the irrigation water. We also discuss possible ways to supply directly the plant with Fe containing compounds, either to the foliage or to the stem. A particular emphasis is given throughout the paper to fruit tree crops growing in Mediterranean areas.     

Mechanisms of plant growth stimulation by humic substances: The role of organo-iron complexes

Abstract

Stimulatory effects of humic substances (HS) on plant growth have been observed and widely documented. Studies have often shown positive effects on seed germination, root initiation and total plant biomass. The consistency of these observations has been uncertain, predominantly due to the lack of understanding of the plant growth promotion mechanism. Often these effects have been attributed to a direct effect of plant growth hormones; whereas in other instances the term “hormone-like activity” has been used to describe the plant growth stimulation (Chen and Aviad, Humic Substances in Soil and Crop Sciences: Selected Readings, American Society of Agronomy, Soil Science Society of America, 1990; Nardi et al., Humic Substances in Terrestrial Ecosystems, Elsevier Science B.V., 1996). Yet, investigators have been unable to prove that plant growth regulators are present in HS preparations, or the evidence provided remains unconvincing. An alternative hypothesis suggesting that growth enhancement of plants grown in nutrient solution (NS) containing HS is the result of improved micronutrient availability, Fe in particular, has been postulated and tested in the present study. Nutrient solutions containing N, P, K, Ca, Mg, S, B, Mo, Cu, Mn, Zn, and Fe at concentrations considered to be optimal for plant growth were tested for solubility of the Fe, Zn, and Mn, 7 days after preparation. In addition to control solutions at pH values of 5, 6, 7, and 7.5, 0 to 200 mg L^?1 of leonardite humic acid (HA) were added to the solutions and they were tested for Fe and Zn solubility. The HA greatly enhanced the maintenance in solution of Fe, in all the tested solutions, and Zn at pH 7.5. Mn mostly remained in solution in its inorganic forms. Plant growth experiments were carried out on both dicotyledonous plants (melons and soybean) and monocotytedonous Poaceae plants (ryegrass), due to the major difference in their Fe uptake mechanism. Plants grown in the absence of Fe exhibited severe Fe deficiency that could only partially be corrected with the addition of mineral Fe salts. The addition of HA or fulvic acid (FA) without addition of Fe, and Zn resulted in partial growth enhancement and correction of Fe deficiency, or none of the two, in the various experiments. This suggests that the growth enhancement effect observed in solutions containing Fe, Zn, and HS was related to the micronutrients rather than to phytohormones. However, the addition of Fe, Zn and either EDTA, HA or FA resulted in healthy, chlorophyll rich plants and enhanced growth, thereby providing evidence that improved Fe, and possibly Zn nutrition is a major mechanism of plant growth stimulation by HS. The use of the term hormone-like activity could be the result of the similarity of the physiological effects obtained in plants enjoying sufficient supply of Fe and Zn.     

Nutritional (Fe-Mn) interactions in ‘Big Top’ peach plants as influenced by the rootstock and by the soil CaCO3 concentration

Manganese (Mn) toxicity in plants is often not a clearly identifiable disorder and it can interfere with the absorption, translocation, and utilization of other elements such as Ca, Mg, Fe, and P. Soil conditions, management factors, and the use of different genotypes of rootstock can determine the degree of Mn toxicity and of interaction with other elements in the orchard. Five plants of the cultivar ‘Big Top’® grafted onto itself, onto plum rootstock ‘Mr.S.2/5’ and onto hybrid peach x almond rootstock ‘GF677’ were grown in 25-L containers under three treatments, 0, 20, 30% concentration of total lime, obtained by mixing powdered CaCO₃ to a sandy soil. Plants were fertilized with manure and a solid fertilizer early in April and irrigated in summer periodically with water rich in manganese. After just 28 d, active lime caused a decrease of chlorophyll SPAD index especially in plants grafted on itself, while those grafted on the tolerant ‘GF677’ rootstock behaved better than those grafted on ‘Mr.S.2/5.’ From June to September, irrigation caused increases in soil Mn concentration and Mn concentration in control plants. This caused first a serious defoliation in Big Top / Big Top plants and then a re-greening of cultivar grafted onto ‘Mr.S.2/5’ and ‘GF677,’ probably due to the interaction between iron and manganese at high pH. In particular the 20% CaCO₃ addition to the soil preserved the plants of cultivar grafted onto ‘Mr.S.2/5’ from Mn toxicity, as shown by their high chlorophyll content and growth and lower Mn leaf concentrations. Plants grafted onto ‘GF677’ rootstock showed the best behaviour under 30% CaCO₃ treatment associated to higher Fe(III)-reducing capacity and photosynthetic activity. Rootstocks and soil conditions (lime and waterlogging) influenced mineral status and growth of the peach cultivar ‘Big Top,’ particularly by interacting together and modifying Fe-Mn availability.     

Alleviation of manganese toxicity and manganese-induced iron deficiency in barley by additional potassium supply in nutrient solution

Barley plants were grown hydroponically at two levels of K (3.0 and 30 mm) and Fe (1.0 and 10 μm) in the presence of excess Mn (25 μm) for 14 d in a phytotron. Plants grown under adequate K level (3.0 mm) were characterized by brown spots on old leaves, desiccation of old leaves, interveinal chlorosis on young leaves, browning of roots, and release of phytosiderophores (PS) from roots. These symptoms were more pronounced in the plants grown under suboptimal Fe level (1.0 p,M) than in the plants grown under adequate Fe level (10 μm). Plants grown in 10 μm Fe with additional K (30 mm) produced a larger amount of dry matter and released less PS than the plants grown under adequate K level (3.0 mm), and did not show leaf injury symptoms and root browning. On the other hand, the additional K supply in the presence of 1.0 μM Fe decreased the severity of brown spots, prevented leaf desiccation, and increased the leaf chlorophyll content, which was not sufficient for the regreening of chlorotic leaves. These results suggested that the additional K alleviated the symptoms of Mn toxicity depending on the Fe concentration in the nutrient solution. The concentration (per g dry matter) and accumulation (per plant) of Mn in shoots and roots of plants grown in 10 μm Fe and 30 mm K were much lower than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that additional K repressed the absorption of Mn. The concentration and accumulation of Fe in the shoots and roots of the plants grown in 10 μm Fe and 30 mm K were higher than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that the additional K increased the absorption of Fe under excess Mn level in the nutrient solution. The release of PS, chlorophyll content, and shoot Fe concentration were closely correlated.     

Diurnal variations in absorption and translocation of a ferrated phytosiderophore in barley as affected by iron deficiency

The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe³⁺ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with ⁵⁹Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of ⁵⁹Fe, The absorption of ⁵⁹Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of ⁵⁹Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of ⁵⁹Fe by roots, The formation of root apoplastic ⁵⁹Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe³⁺ complex by roots did not follow the PS release pattern.