Styliani N. Chorianopoulou

Leaf Responses of Young Iron‐Inefficient Maize Plants to Sulfur Deprivation

Abstract Hydroponically‐grown young iron (Fe)‐inefficient maize (Zea mays L.) plants were deprived of the external source of sulfate following an initial period when the sulfur (S)‐supply was sufficient. The effects of sulfate deprivation on leaf dry weight, dry weight to fresh weight ratio, chlorophyll fluorescence, SPAD reading, nitrogen (N) concentration, and Fe concentration of the lower leaves were monitored for 10 days. The patterns of leaf mass, area, chlorophyll content, and SPAD readings were analyzed according to leaf position. Decreased Fe concentration of leaf tissues was observed in all plants after the fourth day of the experiment, suggesting that this cultivar was Fe‐inefficient. An initial effect of short‐term S‐deprivation on leaves of young Fe‐inefficient maize plants was a lower Fe concentration of lower leaves in the second day. The fourth day of S‐deprivation experiment was a critical stage for the lower leaves, characterized by exhaustion of internal sulfate pools. After day 4, S‐deprivation affected both Fe‐ and N‐concentration of lower leaves. Nitrogen‐concentration remained stable and significantly less than that of the control plants and chlorosis became apparent. From the sixth day onwards, the lower leaves were characterized by decreased dry mass, higher dry weight to fresh weight ratio indicating less water content, less chlorophyll content although existing PSII systems were not affected, lower Fe concentration, and lower N concentration. Leaf development ceased, the fifth leaf did not emerge and the fourth one was less developed, the leaf mass to area ratio of the first three leaves was lowered, a progressive delay in the pattern of partitioning of chlorophyll content among leaves was observed, and the distribution of chlorosis intensity within the leaf blade was altered. Thus, after the sixth day the S‐starved plants experienced a complex constraint consisting of S‐depletion, Fe‐deficiency, and induced N‐deficiency.

FLOWER ANALYSIS FOR PROGNOSIS OF NUTRITIONAL DYNAMICS OF ALMOND TREE

The nutritional fluctuations of almond tree leaves and fruits during their development have been studied to relate the fluctuated nutrient concentrations of these tissues to the nutritional status of flowers. Comparative monitoring for two years in an experimental orchard of almond trees (cv Texas) under integrated production management showed that the analysis of almond tree flowers could be used for the forecast of the elemental dynamics of leaves and fruits of this tree. The values proposed to interpret the elemental analysis of the flowers, under the conditions of this study are: nitrogen (N)=2.8% (± 0.5), phosphorus (P)=0.55% (± 0.10), potassium (K)=2.3% (± 0.2), calcium (Ca)=1.25% (± 0.25), magnesium (Mg)=0.45% (± 0.07), iron (Fe)= 125 ppm (± 25), copper (Cu)=40 ppm (± 8), zinc (Zn)=65 ppm (± 10), and manganese (Mn)=26 ppm (± 4).

DYNAMICS OF NITROGEN AND PHOSPHORUS PARTITION IN FOUR OLIVE TREE CULTIVARS DURING BUD DIFFERENTIATION

Variations of nitrogen and phosphorus levels in reproductive shoots and their leaves of self-rooting olive (Olea europaea) cultivars ‘Amfissis’ (A), ‘Kalamon’ (K), ‘Manzanillo’ (M), and ‘Chalkidikis’ (C) were monitored from the end of harvest until the emergence of the inflorescences. This 90-days period was divided into three sub-periods: before (pre-BD), during (BD), and after (post-BD) bud differentiation. The nitrogen (N)-content in leaves of the reproductive shoots varied between 10–20 mg g−1 and among cultivars the order of decreasing concentration levels was C > K > A > M. The N-content in reproductive shoots varied between 6–14 mg g−1 (K > A > C > M). Patterns of time-course variations are presented. Partitioning of N between leaves and shoots (NL:NS) varied with time, with a ratio between 1.5–2. The fluctuations in the NL:NS ratio over the 90 days showed two distinct phases: during pre-BD either increased (‘Amfissis’ and ‘Chalkidikis’) or remained relatively constant (‘Kalamon’ and ‘Manzanillo’), while during BD and post-BD decreased in all cultivars. The order of decreasing NL:NS ratio among cultivars was K > C > M > A. Phosphorus (P) content in leaves of the reproductive shoots varied between 0.1–2.5 mg g−1, (A > C > K > M). Phosphorus content in reproductive shoots varied between 0.2–1.6 mg g−1, with the highest levels in ‘Amfissis’ compared to the other cultivars. Patterns of P partitioning between leaves and shoots were similar in all cultivars. The PL:PS ratio varied between 0.9–2 (A > C > K > M). The N:P ratio varied between 5:1–20:1 in reproductive shoots and 10:1–35:1 in their leaves, increasing over the examined period. The increase rate of the N:P ratio varied between the three sub-periods, the lowest rate being during BD. The pattern of changes in the N:P ratio was similar in both leaves and shoots and an increase of N:P ratio in leaves was highly correlated with the corresponding increase of N:P in shoots.

Effect of nitrogen fertilization on distribution profiles of selected macronutrients in oriental field‐grown tobacco plants

Abstract As nitrogen (N) fertilization is considered incompatible with oriental tobacco agricultural practice, we studied the influence of N fertilization [no fertilization or ammonium nitrate (NH4NO3) fertilizer applied at either 50 or 100 kg N ha‐1], the growth stage (plant age) and the stalk position (basal, middle, and upper) on the macronutrient phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentration distribution in leaves of the oriental tobacco cv. Myrodata Agriniou. The distribution profiles of leaf P showed an increasing trend from the lower to the upper nodes in all treatments during the vegetative stage up to the fruit set while almost uniform profiles were detected after that. Leaf K, Ca, and Mg accumulation profiles showed decreasing trends from the base to the top over the season. All of the examined macronutrients were accumulated in the lower leaves of the higher fertilized plants late in the season. Leaf dry matter accumulation increased by N fertilization and plant ...

Arbuscular mycorrhizal symbiosis alters the expression patterns of three key iron homeostasis genes, ZmNAS1, ZmNAS3, and ZmYS1, in S deprived maize plants

Nicotianamine is an essential molecule for Fe homeostasis in plants, its primary precursor is the S-containing compound methionine, and it is biosynthesized by the enzyme family of nicotianamine synthases (NASs). In maize, a graminaceous plant that follows Strategy II for Fe uptake, ZmNAS genes can be subgrouped into two classes, according to their roles and tissue specific expression profiles. In roots, the genes of class I provide NA for the production of deoxymugineic acid (DMA), which is secreted to the rhizosphere and chelates Fe(III). The Fe(III)-DMA complex is then inserted to the root via a ZmYS1 transporter. The genes of class II provide NA for local translocation and detoxification of Fe in the leaves. Due to the connection between S and Fe homeostasis, S deficiency causes Fe deprivation responses to graminaceous plants and when S is supplied, these responses are inverted. In this study, maize plants were grown in pots with sterile river sand containing FePO4 and were inoculated with the mycorrhizal fungus Rhizophagus irregularis. The plants were grown under S deficient conditions until day 60 from sowing and on that day sulfate was provided to the plants. In order to assess the impact of AM symbiosis on Fe homeostasis, the expression patterns of ZmNAS1, ZmNAS3 (representatives of ZmNAS class I and class II), and ZmYS1 were monitored before and after S supply by means of real time RT-PCR and they were used as indicators of the plant Fe status. In addition, total shoot Fe concentration was determined before and after S supply. AM symbiosis prevented Fe deprivation responses in the S deprived maize plants and iron was possibly provided directly to the mycorrhizal plants through the fungal network. Furthermore, sulfate possibly regulated the expression of all three genes revealing its potential role as signal molecule for Fe homeostasis.

New insights into trophic aerenchyma formation strategy in maize (Zea mays L.) organs during sulfate deprivation.

Aerenchyma attributes plant tissues that contain enlarged spaces exceeding those commonly found as intracellular spaces. It is known that sulfur (S) deficiency leads to formation of aerenchyma in maize adventitious roots by lysis of cortical cells. Seven-day-old maize plants were grown in a hydroponics setup for 19 days under S deprivation against full nutrition. At day 17 and 26 from sowing (d10 and d19 of the deprivation, respectively), a detailed analysis of the total sulfur and sulfate allocation among organs as well as a morphometric characterization were performed. Apart from roots, in S-deprived plants aerenchyma formation was additionally found in the second leaf and in the mesocotyl, too. The lamina (LA) of this leaf showed enlarged gas spaces between the intermediate and small vascular bundles by lysis of mesophyll cells and to a greater extent on the d10 compared to d19. Aerenchymatous spaces were mainly distributed along the middle region of leaf axis. At d10, –S leaves invested less dry mass with more surface area, whilst lesser dry mass was invested per unit surface area in –S LAs. In the mesocotyl, aerenchyma was located near the scutelar node, where mesocotyl roots were developing. In –S roots, more dry mass was invested per unit length. Our data suggest that trying to utilize the available scarce sulfur in an optimal way, the S-deprived plant fine tunes the existing roots with the same length or leaves with more surface area per unit of dry mass. Aerenchyma was not found in the scutelar node and the bases of the attached roots. The sheaths, the LAs’ bases and the crown did not form aerenchyma. This trophic aerenchyma is a localized one, presumably to support new developing tissues nearby, by induced cell death and recycling of the released material. Reduced sulfur allocation among organs followed that of dry mass in a proportional fashion.

The Application of S 0 -Coated Fertilizer to Durum Wheat Crop

Elemental sulfur (S0) is an ideal slow release S fertilizer with a long history as soil amendment. Recently, S0 has been attached successfully onto the surface of the beads of a commercial fertilizer (F) via a binder (B) by Sulphur Hellas S.A, under the commercial name “Sulfogrow” (FBS0). F beads act as a core effectively covered by an amount of 2% (w/w) of S0 yellow dust. To assess and evaluate the effectiveness of FBS0, we monitored the nutritional dynamics of a durum wheat (Triticum durum, Poaceae) commercial crop. The field was divided into two parts; one subject to control F-treatment, and one with the FBS0-treatment. Rhizosphere pH, organic matter and humic substances contents were monitored, along with the dry mass, and sulfate, total sulfur, organic nitrogen and iron concentrations in the aerial plant part. The FBS0-treated crop presented denser plantation with more robust plants; the accumulated amounts of iron and organic nitrogen per plant were found to be increased at day 61 after sowing in the aerial part by 120% and by 43% respectively, comprising early effects. After day 100, the accumulated dry mass was twice that of control and all accumulation curves were statistically higher than the control ones. The time-course curve of the relative percentage changes (RC) of iron presented in reverse the pattern of sulfate; in contrast, the time-course curve of organic sulfur RC followed the pattern of organic nitrogen RC precisely.

Distribution profile of stomatal conductance and its interrelations to transpiration rate and water dynamics in young maize laminas under sulfate deprivation

Seven-day-old maize (Zea mays) plants were grown hydroponically for 10 days in S-deprived nutrient solution. The distribution profiles according to the position on the stem of the S-deprived laminas’ stomatal conductance, transpiration rate, photosynthetic rate, dry mass, water content, and specific surface area were monitored relative to control among others. Photochemical efficiency of photosystem II remained unaffected by the deprivation, as well as the specific surface area of all but the embryonic laminas after d2. In S-deficient plants, the embryonic (L0) and the uppermost lamina or the one below it presented mostly significant changes. The response ratios (Rr) of the L0 stomatal conductance oscillated; the oscillation started with an increase at d2. The corresponding Rr values of L0 transpiration and photosynthetic rates started oscillating at d4 in the same fashion. At d8, an increasing gradient appeared in water-content Rr values from L1 to the uppermost lamina. At d10, all but the embryonic laminas presented significantly reduced Rr values in water content. Changes in dry mass and surface area of laminas were synchronized. In control, the transpiration rate expressed per DM unit remained constant during the examined period, while under the deprivation it followed a power function of surface area.

A Power Function Based Approach for the Assessment of the Sulfate Deprivation Impact on Nutrient Allocation in Young Maize Plants

Thirteen-day-old maize (Zea mays L.) plants were exposed hydroponically to sulfur (S)-deprivation and their nutritional status was monitored for ten days. Sulfur (S) -deprivation altered the allocation of nutrients between roots and shoots in a differential manner and the effect was approached in terms of a power function. The experimental curvature was analyzed through the value of the exponent of the function and two formulations of the approach were tested through regression analysis. In the shoot, the impact of the S-deprivation relative to that on dry mass was: calcium (Ca) (45.3%) > nitrate (NO3) (18.9%) > magnesium (Mg) (17.2%) > manganese (Mn) (14.1%) > water (W) = phosphorus (P) = potassium (K) = iron (Fe) = copper (Cu) > nitrogen (N) (−4.3%) > ammonium (NH4) (−4.7%) > zinc (Zn) (−12%) > boron (B) (−21.4%) > S (−75.2%). In the root, the relative impact was: N = K = Ca = Zn = B > P (−12.7%) > NO3 (−14.7%) > NH4 (−18.4%) > W (−27.8%) > Mn (−34.4%) > Mg (−37.5%) > Fe = Cu (−40.5%) > S (−126.6%). Both models produced the same conclusions.

Alterations in Short-Term Effect of Oxygen Deficiency on Iron, Manganese, Zinc, and Copper Homeostasis Within Fool's Watercress Organs During Development

Abstract Wetland plants possess various characteristics that enable them to survive oxygen deficiency. Putting forward the hypotheses that the pools of micronutrients may respond to short-term hypoxic and post-hypoxic fluctuations in their rhizosphere at the whole plant level, and that this response may alter with age, we examined for two years the effect of such conditions on the iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) pools of roots, stems, petioles, and leaves of the wetland Apium nodiflorum (Fools watercress) young, mature, and aged plants (2, 6, and 10-month-old, respectively). Young and mature plants behaved almost in the same manner. Iron and Mn levels in the organs of plants experiencing hypoxia did not shift from the normoxic levels. In contrast, Zn and Cu levels increased under oxygen deficiency, but each nutrient presented different behavior. Copper increased in all organs of young and mature plants. Zinc increased only in leaves and roots of young and mature plants. Especially, the increase of Zn in roots was a tremendous one, 6 times above the normoxic levels. Such characteristic increases in Cu and Zn levels were not observed in aged leaves, and petioles. Zinc levels of aged roots almost doubled. Thus, there were alterations in the effect of oxygen deficiency on Zn and Cu homeostasis within A. nodiflorum aged organs, that is, when the plants enter their reproductive stage. The described deviations from normoxic levels may be useful as diagnostic indices of the situation.