Effect of planting date and growth stage on secondary and micronutrient content of soybean tissue

Field experiments were conducted to determine the effect of planting date and cultivar on B, Zn, Mn, Fe, Mg, and Ca content of soybean leaflets, petioles, and stems at beginning bloom (R1), beginning seed (R5) and physiological maturity (R7) growth stages. The concentrations of all the nutrients analyzed were influenced by planting date and cultivar in at least one year. The concentration ranges were: B, 16–167 ppm; Zn, 14–98 ppm; Fe, trace‐575 ppm; Mn, 12–122 ppm; Mg, 0.18–0.89%, and Ca, 0.47–3.02%. As the plants developed, [Fe] generally decreased, [Mn] increased, and [Zn] showed no consistent response. Changes in B, Mg, and Ca concentrations with plant development varied with the plant part. Leaflet [Ca] and [B], and petiole [Ca] and [Mg] increased during seedfill. Petiole and stem [B], and stem [Mg] and [Ca] decreased during seedfill.     

An examination of Fe deficiency stress response in relation to Fe uptake in two sorghum hybrids and their parent cultivars

Two sorghum (Sorghum bicolor L. Moench) hybrids CSH‐10 and ‐ 11 and their parent cultivars 296‐A, SB‐1055 and MR‐715 were examined for their tolerance to Fe‐deficiency stress, and also Fe uptake. It was observed that there was greater reduction of pH of the nutrient media and more rapid recovery from chlorosis only in the female parent 296‐A, and to some degree in the hybrids, but not in the male parents. The results indicated that Fe uptake‐translocation were inversely related to their Fe stress tolerance.     

Fe Deficiency Responses in Parietaria diffusa: A Calcicole Plant

Abstract

Pellitory of the wall (Parietaria diffusa L.), a dicotyledonous wild plant belonging to the family of Urticaceae, is widespread on calcareous soils, and also on walls and debris, were lime concentration, sometimes, is extremely high; it may then be considered a calcicole plant. Since high pH values and the presence of CaCO₃ and HCO₃ ^? cause low Fe solubility, its availability in such substrates could be the ecological factor limiting the distribution of spontaneous plants in calcareous soils, and a calcareous soil‐born plant should be characterized by a higher Fe‐efficiency in comparison with calcifuge ones. Parietaria diffusa was grown in nutrient solutions in the presence and in the absence of Fe, and in the presence of CaCO₃ and bicarbonate at two concentrations (5 and 15 mM), in order to simulate a natural substrate with different lime contents. Some biochemical parameters were determined and the morphological and hystological modifications of the root system were evaluated in order to verify whether Parietaria is a Fe‐efficient plant and adopts the adaptive mechanisms of Strategy I Fe‐efficient plants.     

Activities of Iron‐Containing Enzymes in Leaves of Two Tomato Genotypes Differing in Their Resistance to Fe Chlorosis

Abstract

Two tomato (Lycopersicon esculentum Mill., cvs. Pakmor and Target) genotypes differing in resistance to iron (Fe) deficiency were grown in nutrient solution under controlled environmental conditions over 50 days to study the relationships between severity of leaf chlorosis, total concentration of Fe, and activities of Fe‐containing enzymes in leaves. The activities of Fe‐containing enzymes ascorbate peroxidase, catalase, and guaiacol peroxidase, and additionaly the activity of glutathione reductase, an enzyme that does not contain Fe, were measured. Plants were supplied with 2 × 10^?7 M (Fe deficient) and 10^?4 M (Fe sufficient) FeEDTA, respectively. Leaf chlorosis appeared more rapidly and severely in Target (Fe deficiency senstive genotype) than Pakmor (Fe deficiency resistant genotype). On day 50, Pakmor had 2‐fold more chlorophyll than Target under Fe deficiency, while at adequate supply of Fe the two genotypes were very similar in chlorophyll concentration. Despite distinct differences in development of leaf chlorosis and chlorophyll concentrations, Pakmor and Target were very similar in concentrations of total Fe under Fe deficiency. In contrast to Fe concentration, activities of Fe‐containing enzymes were closely related to the severity of leaf chlorosis. The Fe‐containing enzymes studied, especially catalase, showed a close relationship with the concentration of chlorophyll and thus differential sensitivity of tomato genotypes to Fe deficiency. Glutathione reductase did not show relationship between Fe deficiency chlorosis and enzyme activity. The results confirm that measurement of Fe‐containing enzymes in leaves is more reliable than the total concentration of Fe for characterization of Fe nutritional status of plants and for assessing genotypical differences in resistance to Fe deficiency. It appears that Fe deficiency‐resistant genotype contains more physiologically available Fe in tissues than the genotype with high sensitivity to Fe deficiency.     

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.     

Iron transport in plants: Future research in view of a plant nutritionist and a molecular biologist

Iron is attractive to plant physiologists since J. Sachs has proven in 1868 the essentiality and the possible leaf uptake of Fe. It lasted about 100 years before the principal processes for Fe mobilization in the rhizosphere were discovered and classified as two distinct strategies for Fe acquisition. During the 80's and 90's of the last century the uptake of Fe²⁺ and Fe^III-phytosiderophores by specific transporters in strategy I- and strategy II-plants, respectively, were postulated without any application of the new approaching molecular techniques. In the following decade, the various transporters for Fe uptake by roots, such as AtIRT1 in Arabidopsis or ZmYS1 in maize and their possible regulation were characterized. In the following years with fast developing molecular approaches further Fe trans ortsrs were genetically described with often only vague physiological functions. In view of a plant nutritionist, besides uptake processes by roots, the following transport processes within the respective target tissue have to be considered by molecular biologists in more detail: 1) radial transfer of Fe from the root cortex through the endodermis, 2) xylem loading in roots, 3) transfer of Fe from xylem to phloem via transfer cells, 4) phloem loading with Fe in source leaves and retranslocation to sink organs, and 5) remobilization and retranslocation via the phloem during senescence of perennial plants. The importance of these various specific transport processes for a well-regulated Fe homeostasis in plants and new strategies to identify and characterize proteins involved in Fe transport and homeostasis will be discussed.     

Regulation and function of AtNRAMP4 metal transporter protein

The NRAMP gene family encodes integral membrane proteins mediating the transport of a broad range of transition metals in bacteria, fungi, plants, and animals. We studied the regulation of AtNRAMP4 in Arabidopsis. In a previous study, we showed that AtNRAMP3 and AtNRAMP4 transport manganese (Mn), iron (Fe), and cadmium (Cd). In this study, we show that, in contrast to AtNRAMP3, AtNRAMP4 complements the growth phenotype of the zrt1zrt2 Zn uptake deficient yeast mutant. In a previous study, we have shown that, under Fe starvation, AtNRAMP4 mRNA levels are up-regulated in Arabidopsis. To analyze the regulation of AtNRAMP4 at the protein level, we generated specific antibodies against AtNRAMP4 protein. The antiserum was able to recognize a tagged version of AtNRAMP4 expressed in yeast. The antibody did not reveal any change in AtNRAMP4 protein level upon Fe starvation in Arabidopsis thaliana ecotype Columbia plants. In AtNRAMP4 overexpressing plants, high levels of AtNRAMP4 protein could be detected. AtNRAMP4 overexpressing plants display cadmium hypersensitivity in a medium containing 50 μm FeEDTA as Fe source. However, despite the constitutive accumulation of AtNRAMP4 protein, AtNRAMP4 over-expressing plants did not display Cd hypersensitivity under high Fe supply (100 μm FeHBED). AtNRAMP4 over-expressing lines displayed the same sensitivity to Zn as controls under all conditions tested. Our results suggest a translational level for the regulation of AtNRAMP4. Over-expression of AtNRAMP4 in Arabidopsis thaliana confers a slight hypersensitivity to Cd but not to Zn.     

Overcoming Fe deficiency in guava (Psidium guajava L.) by co-situs application of controlled release fertilizers

Abstract

Among micronutrient deficiencies, Fe deficiency is the most difficult nutritional disorder to prevent in the fruits of trees growing on calcareous soils. In this study, a pot experiment was carried out to evaluate the potential of co-situs application of controlled release fertilizers (CRF) in alleviating Fe deficiency and improving the growth of fruit trees growing on calcareous soil (pH 9.3). Guava (Psidium guajava L.) seedlings were used as test plants because of their sensitivity to Fe deficiency. Treatments consisted of the following: (1) broadcast application of readily soluble Fe, Zn, Cu, B and Mn fertilizers (Control) or (2) co-situs application of CRF containing N, P, K, Mg, Fe, Zn, B, Cu and Mn (Co-situs). For the Control treatment, CRF containing only N, P and K was used. Both treatments received the same amount of all nutrients. Plants were more chlorotic in young leaves under the Control treatment and the Fe content of young leaves was significantly (least significant difference [LSD_0.05]) higher under the Co-situs treatment. Dry matter production of shoots under the Co-situs treatment was 5.2-fold higher than under the Control treatment, and the total accumulations of macro and micronutrients were much higher under the Co-situs treatment than the Control treatment. Total accumulations of N, P, K, Ca and Mg were 5.0, 4.1, 9.6, 3.2 and 2.2-fold higher, respectively, under the Co-situs treatment compared with the Control treatment, and Fe, Zn, Cu and Mn accumulations were 3.2, 4.1, 6.0 and 3.7-fold higher, respectively. Iron deficiency in guava seedlings was successfully alleviated by the co-situs application of controlled fertilizer, proving the high potential of this method in alleviating Fe deficiency in fruit trees growing on calcareous soils.     

Midsummer copper sprays have no effect on ‘delicious’ apple fruit color grade or typiness

Recent reports suggested that multiple midsummer copper (Cu) sprays could improve the proportion of apple fruit (Malus × domestica Borkh.) being packed in the reddest market color grades. We conducted a three‐year field experiment in a low‐Cu orchard with a history of poor fruit coloring. We applied multiple mid‐summer sprays of Cu sulfate and basic Cu sulfate in 1994 and 1995 to ‘Bisbee Delicious’ and ‘Oregon Spur II Delicious’ apple trees. Plant tissue nutrient levels, fruit color grade, and fruit typiness were evaluated in the years of application and the following year. The Cu sprays increased leaf Cu in the years of application; however, leaf Cu in the Cu‐sprayed plots returned to or very near to background concentrations in the year after sprays were terminated. The Cu treatments did not increase the proportion of fruit in the reddest market color grades or influence five fruit typiness indices of either apple cultivar. Although midsummer Cu sprays may not enhance apple fruit red color or typiness, they may be useful for increasing overall tree Cu status, particularly for long‐season cultivars which are harvested too late for postharvest sprays to be effective.     

Relationship Between Iron Deficiency Stress and Endogenous Hormones in Iron-Efficient versus Inefficient Apple Genotypes

In solution culture at different iron (Fe) concentrations, both contents of endogenous hormones or the IAA oxidase activities in the roots and the diffusive IAA contents in the stem apex were analyzed for Malus xiaojinensis (an Fe-efficient apple genotype) or M. baccata (an Fe-inefficient apple genotype). The results showed that higher amounts of IAA in M. xiaojinensis were transported from the stem apex into roots under Fe deficiency stress, which resulted in a great enhancement of the root IAA content, being 4–5 times higher at Fe deficiency than at a normal Fe level. Root IAA content of M. baccata did not show any obvious change at both deficiency and normal level of Fe. When the appearance of leaf chlorosis was used as the test point by the time, there was no remarked difference in fluctuation of the root GA₃ or ABA contents between M. xiaojinensis and M. baccata, although the developing trends of the root GA₃ or ABA contents were slightly lagging for M. xiaojinensis. The results obtained in this experiment suggested that IAA might be a signal factor of inducing Fe deficiency response in plant of genus Malus.