David Wm. Reed

Iron chlorosis development and growth response of peach rootstocks to bicarbonate 1

Abstract For dicots, bicarbonate (HCO3‐) is regarded as a main factor in the induction of iron (Fe) chlorosis in calcareous soils, and sand and solution culture. In sand culture experiments, peach [Prunus persica (Batsch) L.] rootstock developed chlorosis only when HCO3‐ levels were equal to or higher than 6 mM. Above this level, chlorosis increaeed as HCO3‐ level was increased. In spite of the lack of chlorosis at to or below 6 mM of HCO3‐, large growth reductions (40–60% reduction in fresh shoot weight) were seen in all rootstocks, although the tolerant rootstock had less reduction than the more susceptible rootstocks. Shoot growth was affected by HCO3‐ more than was root growth.

Field evaluation of inorganic and chelated iron fertilizers as foliar sprays and soil application

Abstract A series of inorganic and chelated ferric and ferrous fertilizers were tested for their ability to alleviate Fe chlorosis as foliar and soil application on peach and grape under field conditions. Limited re‐greening was obtained with foliar application of ferric citrate/ammonium nitrate, ferrous sulfate and DTPA on peaches, and with foliar application of ferric citrate/ammonium nitrate and ferrous sulfate and soil application of ferric citrate/ammonium sulfate and ferric citrate/urea/ammonium nitrate on grapes. The only treatments that resulted in complete elimination of iron deficiency, as indicated by complete re‐greening and plant rating, was soil application of EDDHA on both peach and grape. Soil application of methyl‐EDDHA was almost as effective as EDDHA, resulting in slightly less intense re‐greening and chlorophyll content.

Influence of bicarbonate level on iron-chlorosis development and nutrient uptake of the peach rootstock Montclar

Abstract The peach rootstock Montclar [Prunus persica (Batsch) L.] was grown in sand culture supplied with half‐strength nutrient Hoagland No. 1 solution with 10 μM FeEDDHA at seven bicarbonate (HCO3‐) levels: 0, 2, 5, 10, 15, 20, and 25 mM. Montclar developed chlorosis only at HCO3‐ levels ≥ 10 mM. Above this level, chlorosis increased as HCO3‐ level was increased. When HCO3‐level increased, the contents of N, P, K, Ca, Mg, Fe, and Mn decreased; the concentrations of N, P, Ca, and Fe in the new branch growth decreased, but that of Mg and Mn did not change. The partitioning of N, P, Ca, Mg, and Fe to the new branch growth decreased, while the partitioning of K and Mn did not change. The partioning of Fe to the new branch growth decreased more than the partitioning of the other nutrients when the HCO3‐ levels were higher than 10 mM. At low HCO3‐ levels (< 10 mM), active‐Fe content decreased with increasing HCO3 − level, even though no chlorosis was observed. The correlation between chlorosis and Fe concent...

Response of Selected Greenhouse Ornamental Plants to Alkalinity in Irrigation Water

ABSTRACT Tolerance to alkalinity was evaluated in rose ‘Pink Cupido,’ ivy geranium ‘Peppermint Candy,’ vinca ‘Apricot Delight,’ chrysanthemum ‘Miramar,’ hibiscus ‘Bimini Breeze’ and ‘Mango Breeze’ plants irrigated with solutions containing 0 to 10 mM sodium bicarbonate (NaHCO3). The minimum toxic threshold of NaHCO3 was established as a 10% decrease from the control in chlorophyll concentration (as determined by the SPAD index) and shoot dry mass, which were estimated by using regression models. The ranking for susceptibility to NaHCO3-induced chlorosis was: rose > hibiscus ‘Mango Breeze’ > ivy geranium > chrysanthemum > hibiscus ‘Bimini Breeze” > vinca, with toxic thresholds of 0.8, 2.1, 2.4, 3.2, 4.2, and 6.8 mM NaHCO3, respectively. The ranking for susceptibility to NaHCO3-induced shoot dry mass reduction was: rose > hibiscus ‘Mango Breeze’ ≈ ivy geranium ≈ chrysanthemum ≈ hibiscus ‘Bimini Breeze” > vinca, with toxic thresholds of 2.0, 7.3, > 10, > 10, > 10, > 10 mM NaHCO3, respectively.

Physiological characterization of two peach seedling rootstocks in bicarbonate nutrient solution. I. Root iron reduction and iron uptake

Investigations were conducted on two peach seedling rootstocks, Nemaguard and TXR4989-2 (hybrid Titan × Nemared’), grown in bicarbonate-containing nutrient solution with 50 μM Fe-DTPA. Root-associated Fe(III)-reductase activity and iron absorption were determined to elucidate the physiological differences which cause the different tolerance of the two rootstocks in calcareous soils. Reductase activity was detectable in intact plants after several weeks and visualized on excised roots in gelrite medium. The physiological responses of NMG and TXR rootstocks suggest that stress conditions increase the Fe-reduction capacity and the iron uptake enormously. Both assays indicated interesting differences in behaviour between rootstocks.

GROWTH AND NUTRITION OF YOUNG BEAN PLANTS UNDER HIGH ALKALINITY AS AFFECTED BY MIXTURES OF AMMONIUM, POTASSIUM, AND SODIUM

High concentrations of bicarbonate (HCO− 3) cause alkalinity of irrigation water and are associated with suppression in plant growth and micronutrient deficiencies, such as iron (Fe) and zinc (Zn). Because reports indicate that the deleterious effects of alkalinity may be counteracted partially by supplementary potassium (K+) or ammonium (NH4 +) an experiment was designed to evaluate the response of bean plants (Phaseolus vulgaris L.) grown in high alkalinity conditions to varying proportions of NH4 +, K+, or sodium (Na+) (as a potential substitute for K+). Plants established in a growth chamber were grown in hydroponics for 21 days in solutions containing 5 mM HCO− 3 and a total of 5 mM of a mixture of NH4 +, K+, and Na+. The proportions of NH4 +, K+, and Na+ were designed according to mixture experiment methodology. Total N in all the mixture treatments was maintained at 10 mM by using nitrate (NO− 3)-N, thus the NH4 +:NO− 3 ratio varied according to the proportion of NH4 + in the mixtures. Alkalinity caused suppression in plant growth and chlorophyll concentration in the younger leaves, whereas excessive NH4 + was associated with leaf scorching and decreased leaf expansion. High proportions of K+ alleviated alkalinity symptoms and produced higher shoot and root dry mass provided that NH4 + was included in the mixture. However, a proportion of NH4 + higher than 0.333 in the mixture (>1.66 mM NH4 +) induced toxicity. The highest shoot dry mass occurred if the NH4 +:NO− 3 ratio was 0.19:0.81 and the NH4 +:K+:Na+ proportion was 0.38:0.38:0.24 (1.9 mM NH4 + + 1.9 mM K+ + 1.2 mM Na+). Thus, an improvement in plant growth is achieved when NH4 +, K+, and Na+ are blended together, in spite of the high alkalinity treatment imposed. Optimum NH4 + was associated with a decrease in solution pH and an increase in shoot Fe and Zn concentration.

Iron stress response of three peach rootstock cultivars: Ferric‐iron reduction capacity 1

Abstract Three peach rootstocks were evaluated for their capacity to reduce ferric‐iron (Fe3+) after iron‐stress treatment. Neither of the rootstocks with tolerance to iron (Fe) chlorosis [Titan1 x Nemaguard (Prunus dulcis (all.) D. A. Webb x Prunus persica (Batsch) L.] nor ‘Montclar’ (P. persica) showed consistently higher Fe‐stress induced Fe3+ reduction/g root fresh weight (RFW) compared to the less tolerant rootstock Nemaguard [(P. persica)]. However, non‐stressed ‘Titan’ x Nemaguard (TNG) showed higher leaf chlorophyll content than both ‘Montclar’ (MC) and Nemaguard (NG) and higher mean Fe3+ reduction by root released reductants than Nemaguard. The reduction rate by root released reductants was approximately 22–34% for NG, 15% for MC, and 29% by TNG. ‘Titan’ x Nemaguard and Montclar maintained better root growth (i.e., had less root necrosis) under Fe‐stress than NG which resulted in greater Fe3+ reduction per plant. This indicates that the maintenance of a greater root surface area during Fe‐stress ...

Influence of Potassium Substitution by Rubidium and Sodium on Growth, Ion Accumulation, and Ion Partitioning in Bean under High Alkalinity

ABSTRACT The effects of partial and complete substitution of potassium (K+) by rubidium (Rb+) and sodium (Na+) on plant growth and ion accumulation and partitioning was studied in bean young plants cultivated in nutrient solution with or without bicarbonate (HCO3 −)-induced alkalinity. Plant growth was significantly decreased due to alkalinity and the substitution of K+, being leaves more affected than roots. Rubidium caused a severe toxicity reflected in a reduction in root dry mass and total chlorophyll concentration. Ion partitioning was markedly altered by alkalinity. Content of nitrogen (N), calcium (Ca), magnesium (Mg), iron (Fe), K, and Na were more accumulated in the roots in HCO3 −-treated plants, while decreased in the shoot. Iron (Fe) was accumulated at similar extent in plants with and without high alkalinity, except in plants grown in Rb+ solutions. However, Fe was more accumulated in the roots, suggesting that chlorophyll synthesis was impaired by reduced translocation or internal inactivation of Fe. Zinc total uptake was severely reduced under high alkalinity in plants grown in Na+ solutions, maybe due to decreased Zn activity. Calcium was translocated more actively to the leaves and Mg was accumulated more in the roots of plants in Na+solutions. Despite the severe decrease in plant dry mass caused by Rb+, there was a higher translocation of N, phosphorus (P), Ca, Mg, Fe, zinc (Zn), copper (Cu), and manganese (Mn) from the roots to the leaves.

The foliar absorption of potassium from organic and inorganic potassium carriers

Abstract Using excised trifoliate leaves of 3 week‐old Glycine max ‘Bragg’ seedlings, a total of 31 organic and inorganic potassium compounds were tested for their efficacy of foliar potassium absorption at 10 mM K (using 86Rb as a tracer for K) and pH 6.3. Of the 14 inorganic K compounds screened, potassium bicarbonate, nitrite and several phosphate compounds yielded the highest % K absorption. Five of the inorganic K compounds caused slight leaf burn. Most of the 17 organic K compounds yielded higher % K absorption than the inorganic K compounds. Potassium acetate had the highest % K absorption without causing leaf burn. Monocarboxylic K compounds had greater % K absorption than the di‐ and tricarboxylic compounds. Chemical groups which increased polarity tended to decrease absorption. The absorption data for all K compounds tested could be partially explained by considering molecular weights and drying characteristics on the leaf surface. There was a positive correlation between total % K absorption an...

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

Abstract 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.