Plant Fe Content Research Articles

Iron Chlorosis in Gerber as Related to Properties of Various Types of Compost used as Growing Media

Nutrient deficiencies in crop plants may be influenced by a number of properties of the growing media. Some peat‐substitute substrates can promote iron (Fe) chlorosis in sensitive plants, which has traditionally been ascribed to the elevated pH of growing media. To identify the origin of this problem in various types of composted organic residues used as growing media and possible corrections, a complete randomized experiment on gerber (Gerbera jamesonii Adlam) as an Fe‐chlorosis sensitive crop involving three factors (growing medium, medium acidification, and the medium treatment with Fe) was performed. Although the Fe content in plants decreased with increasing pH in the growing medium, the chlorophyll content as measured using a chlorophyll meter (Minolta Soil Plant Analysis Development, SPAD) was not significantly related to pH. The SPAD readings and Fe concentrations in plants, dry matter, and flower production were not significantly related to diethylenetriaminepentaacetic acid (DTPA)–extractable Fe in the growing media. The addition of Fe‐chelate significantly increased yield (P<0.01), and SPAD at 65 and 96 days after planting (P<0.001 and P<0.01, respectively). However, the effect of the acid treatment was, different depending on the growing media. When the acidification promoted a positive effect on SPAD readings, this was nonsignificantly different than that obtained with the application of Fe‐chelate. The estimated amount of available Fe in the growing media was not relevant, which explains the incidence of chlorosis as physiological factors related to pH.

Iron nutrition affects cadmium accumulation and toxicity in rice plants

The effect of iron (Fe) nutrition on cadmium (Cd) toxicity and accumulation in rice plants was studied using a hydroponic system. The inhibitory effect of Cd on plant growth and chlorophyll content (SPAD value) was dependent on Fe level and the genotype. Malondialdehyde (MDA) content in leaves and roots was not much affected by an increased Cd stress at 0.171 mg l−1 Fe, but it showed a rapid increase when the plants were exposed to moderate (1.89 mg l−1) and high (16.8 mg l−1) Fe levels. High Fe nutrition caused a marked reduction in Cd content in both leaves and roots. Fe content in plants was lower at high Cd (5.0 μM) stress than at low Cd (<1.0 μM) stress. Cd stress increased both superoxide dismutase (SOD) and peroxidase (POD) activities at low and moderate Fe levels. However, with high Fe level, it increased the POD activity, but reduced the SOD activity. Our results substantiate the hypothesis that cell membrane-bound iron transporter (carrier) involved in high-affinity iron transport systems can also transport Cd, and both these ions may compete for this common carrier. The study further showed that there were significant correlations between MDA and Fe contents in leaves and roots of rice plants. It is suggested that the occurrence of oxidative stress in plants exposed to Cd stress is mediated by Fe nutrition. The present results also show that Cd stress affects the uptake of Cu and Zn.

Toxicity level for phytoavailable zinc in compost–peat substrates

Petunias were grown in compost–peat substrates with different Zn contents (basic load, 400, 800, and 1600 mg kg –1) in order to identify toxic levels of Zn in plant dry matter and of phytoavailable (CaCl 2-extractable) Zn in compost–peat substrates. Yield reduction of petunias was only observed at an extremely high Zn content (635 mg Zn kg –1 plant d.m.), although chlorosis was evident at lower Zn levels (160 mg Zn kg –1 plant d.m.). Thus, the occurrence of Zn-induced chlorosis during the growth period was chosen as the toxicity parameter. Chlorosis and plant Zn content were reduced by additional Fe supply, although the Fe content of the plants was not affected. During a six week growth period, petunia Zn content and chlorosis increased in the first two and three weeks, respectively, and then decreased, whereas plant Fe content decreased sharply between the second and third week after the start of Zn treatment. Chlorosis first occurred with a plant Zn content of 160 mg kg –1, corresponding to a CaCl 2-extractable Zn content in the substrate of 6 mg l –1, which was identified as the toxicity level for phytoavailable Zn in compost–peat substrates. Taking a safety factor into account, a critical level of 4.5 mg l –1 was computed, which should not be exceeded in order to avoid Zn-induced chlorosis.

Nutrient Uptake in Poinsettia during Different Stages of Physiological Development

`Supjibi' poinsettias (Euphorbia pulcherrima Willd.) were grown hydroponically for 15 weeks in nutrient solutions with 100-15-100, 200-30-200, or 300-46-300 (in mg·L-1 of N-P-K) to determine nutrient uptake patterns and accumulation rates. Results indicate that increasing fertilization rates from 100 to 300 mg·L-1 of N and K did not significantly influence the plant dry mass or the nutrient concentration of P, K, Ca, Mg, Na, B, Cu, Fe, Mn, Mo, and Zn in poinsettias. NH4-N concentration in the leaves, stems, and roots were lowest with the 100-mg·L-1 N fertilization rate and increased as the N application rate increased to 200 and 300 mg·L-1. Leaf P concentration levels from 1 week after potting through anthesis were above 1.3%, which exceeds the recommended level of 0.9%. When the plant tissue dry mass for each fertilizer rate was transformed by the natural log and multiplied by the mean tissue nutrient concentration of each fertilizer rate, there were no significant differences among the three fertilization rates when the total plant nutrient content was modeled for N, P, or K. Increasing the fertilizer application rate above 100 mg·L-1 N and K and 15 mg·L-1 P decreased total plant content of Ca, Mg, Mn, and Zn and increased the total plant Fe content. The results of the weekly nutrient uptake based on the total plant nutrient content in this study suggests that weekly fertilization rates should increase over time from potting until anthesis. Rates (in mg) that increase from 23 to 57 for N (with 33% of the total N supplied in the NH4-N form), 9 to 18.5 for P, 19 to 57 for K, 6 to 15 for Ca, and 3 to 8 for Mg can be applied without leaching to poinsettias and produce adequate growth in the northern United States.

Effects of heavy metals on both induction and function of root Fe(lll) reductase in Fe-deficient cucumber (Cucumis sativusL.) plants

Heavy metals are known to induce Fe chlorosis in different plant species. Heavy-metal-induced chlorosis is generally correlated with low plant Fe contents, suggesting effects of heavy metals on Fe mobilization and uptake. Under Fe-deficient conditions, dicotyledonous plants enhance root Fe(III) reductase activity, thus increasing the capacity to reduce Fe(III) to Fe(II), the form in which roots absorb Fe. We studied the effect of several heavy metals (Mn, Pb, Zn, Mo, Ni, Cu, and Cd) on the induction of enhanced root Fe(III) reductase by 11 -d-old Fe-deficient cucumber (Cucumis sativus L. cv. Ashley). The effect of these heavy metals on the function of the induced Fe(III) reductase was also investigated. Results showed that some heavy metals can inhibit both the induction and function of root Fe(III) reductase. Ni, at 20 μM, and Cu and Cd, at 5 μM concentration or higher, severely inhibited the induction of root Fe(III) reductase while Mn, Pb, Zn, and Mo had little effect, even at concentrations higher than 20 μM. Function of the induced root Fe(III) reductase only was negatively affected by Cu and Ni

Blood powder, a source of iron for plants

Abstract Natural materials that possess chelating ability for iron (Fe) such as plant and animal residues have been used as Fe sources for plants. A solution culture study and a soil incubation study were conducted to investigate use of poultry blood powder as an Fe source for plants. Iron in blood is chelated by the heme group present in hemoglobin molecule. Stability of Fe in this chelate was found to be high in neutral and acidic solutions. Only a very small fraction (0.1 to 0.2%) of total Fe could be extracted from blood powder by a 0.1M calcium chloride (CaCl2) solution. In the culture solution study, Fe from blood powder was as effective as Fe from FeEDDHA in preventing Fe chlorosis of soybeans. Yield and Fe content of plants receiving blood powder were higher than the control and were not different from the plants receiving FeEDDHA. The incubation study using two soils, two Fe sources and three Fe rates indicated that DTPA‐Fe increased from application of 5, 10 or 15 mg of Fe as blood powder/kg in ...

CORN YIELD VARIABILITY AND UPTAKE OF VARIOUS NUTRIENTS IN RESPONSE TO PHOSPHORUS FERTILIZATION IN LOW-P SOILS

Phosphorus was either banded, broadcast, or incorporated into raised beds at 33, 66, 99, or 132 kg·ha-1. Sweet corn was planted in two rows 30 cm apart on the beds. Substantial differences in plant growth were observed between the two rows on each bed. Yield response to P treatments was masked by this variability. Plant tissue samples were collected at mid-season and at harvest time, and were analyzed for P, K, Ca, Mg, Zn, and Fe. Strong positive correlations were found between corn yield and plant Fe content, and strong negative correlations were found between corn yield and plant Zn content. Phosphorus content of tissue was positively correlated with plant Fe and negatively correlated with plant Zn content. Differences in plant height measured at mid-season could not be explained by nutrient concentrations in the tissue at that time. Corn ear yield was best explained by Fe concentration of the shuck (positive correlation), and by zinc concentration of the foliage (negative correlation) at harvest time. The range in ear weight was greater with the banded P treatments than with broadcast or incorporated P.

Effects of Seasonal Interactions of Nitrogen, Phosphorous, and Potassium Fertilizers on Yield and Nutrient Content of Snap Beans (Phaseolus vulgaris L.)1

Abstract Pod yields, nutrient content of plant tissues, and NO3-N accumulation in pods were determined for snap beans grown at 4 N and 2 P-K levels in the spring and fall seasons of 1968 and 1969. Increased N applications resulted in increased pod yields, higher levels of K, Ca, Mg, and Zn in the plants, and accumulation of NO3 in pods; however, the NO3 effects varied between years. Applied P-K reduced pod yield, increased Fe content of plants but antagonized Mg and Zn uptake. Of plant parts, pods accumulated the most N, P, and Zn; leaves, the most K, Ca, Mg, Fe, and Mn; and stems, the most Cu. Seasonal influence of N and P-K application rate on yield was not consistent. In general, beans had higher nutrient content in the spring than in the fall. Translocation of K, Ca, Fe, and Cu was influenced by season.