Shoot Elongation Research Articles

Role of gibberellin and its three GID1 receptors in Jasminum sambac stem elongation and flowering.

Taken together, our results establish a reciprocalrelationship between vine elongationandflowering, and reveal that GA is a positive signal for stem elogation but a negative regulator of flowering in this species. Vines or climbing plants exhibit vigorous vegetative shoot extension. GA have long been recognized as an important signal for seasonal stem elongation and flowering in many woody perennials. However, less is explored as how GA pathway is involved in the regulation of shoot extension in woody vines. Here, we investigated the role of GA and its signaling components in shoot elongation in Jasminum sambac. We found high accumulation of GA4 in the elongating internode, in contrast to a depletion of GAs in the floral differentiating shoot, which in turn featured a higher zeatin content, and a lower IAA and JA concentrations. This GA accumulation was coincident with the strong expression of JsGA20ox1 and JsGAS1 in the leaves, as well as of the JsGA2ox3 in the internode. Treatment of GA biosynthesis inhibitor reduced elongation while stimulated the terminal flowering. Remarkably, three B-type GA-receptor genes were abundantly expressed in both internodes and leaves of the extending shoots, which could enhance GA responsiveness in heterologous transgenic Arabidopsis. Furthermore, these JsGID1s showed distinct GA-dependent interaction with the JsDELLA in a yeast-two-hybrid assay. Taken together, our results establish a reciprocal relationship between vine elongation and flowering, and reveal that GA is a positive signal for stem elogation but a negative regulator of flowering in this species.

Straightening the crooked: intraspecific divergence of stem posture control and associated trade-offs in a model conifer.

Although the straightening capacity of the stem is key for light capture and mechanical stability in forest trees, little is known about its adaptive implications. Assuming that stem straightening is costly, trade-offs are expected with competing processes such as growth, maintenance, and defence. We established a manipulative experiment in a common garden of Pinus pinaster including provenances typically showing either straight-stemmed or crooked-stemmed phenotypes. We imposed a bending up to 35º on plants aged 9 years of both provenance groups and followed the straightening kinetics and shoot elongation after releasing. Eight months later, we destructively assessed biomass partitioning, reaction wood, wood microdensity, xylem reserve carbohydrates, and phloem secondary metabolites. The experimental bending and release caused significant, complex changes with a marked difference between straight- and crooked-type plants. The straight-type recovered verticality faster and to a higher degree and developed more compression wood, while displaying a transitory delay in shoot elongation, reducing resource allocation to defence and maintaining the levels of non-structural carbohydrates compared with the crooked type. This combination of responses indicates the existence of intraspecific divergence in the reaction to mechanical stresses that may be related to different adaptive phenotypic plasticity.

Identification of QTLs for stagnant flooding tolerance in rice employing genotyping by sequencing of a RIL population derived from Swarna × Rashpanjor.

The online version contains supplementary material available at 10.1007/s12298-021-01107-x.

Localised photosynthetic pigments in the node of a holoparasitic plant: support for shoot growth?

Understanding the role of photosynthesis in the holoparasitic genus Cuscuta may give insights into the biology and evolution of these plants. We hypothesised that light irradiance on the node of C. racemosa is important for sustaining the growth of the new shoot through photosynthesis. We blocked light irradiance on the node of detached twigs of C. racemosa for one week and measured twig fresh and dry weight, shoot length and photosynthetic pigment content. Even though fresh and dry weight did not differ between non-irradiated and irradiated twigs, the shoots of non-irradiated nodes were significantly shorter. The non-irradiated plants showed higher amounts of chlorophyll a, b, and lycopene, and a lower concentration of β-carotene. Furthermore, the chlorophyll a/b ratio was lower than that of the control (irradiated) plants. Beyond corroborating our hypothesis, our results suggest that, when light is blocked on the node of C. racemosa, the holoparasite responds in a way similar to that of autotrophic plants under shaded conditions. Our findings suggest a new and previously unacknowledged role for the node of C. racemosa, which would be supporting shoot elongation through photosynthesis.

Allelopathy effects of invasive alien Ageratina adenophora on native shrub species of chir pine forest in the central Himalaya, India

ABSTRACT Ageratina adenophora Spreng. is one of the most troublesome invasive species that has invaded various forest ecosystems in the central Himalaya. The chir pine (Pinus roxburghii Sarg.) forests in the region facing a high risk of invasion and loss understory diversity of native species. The present study comprehends the allelopathy effect of the invasive species A. adenophora residues bioassay (extract) and soil amendment against two co-occurring native shrubs viz Berberis asiatica Roxb. Ex DC. and Rubus ellipticus Sm. in a laboratory and natural forest conditions. Results revealed that a higher concentration (4% and 8%) of A. adenophora leaf, root and shoot extract have significantly inhibited (23% to 76%) and low concentration (1%) did not inhibit the seed germination, root and shoot length of B. asiatica and R. ellipticus. Furthermore, 8% (w/w) A. adenophora residue (leaf, root and shoot) amendments with the natural soil also showed significant inhibition effects (13% to 37%) on seedling growth and biomass of both the test species. Weekly A. adenophora leaf residue amendment showed higher inhibition in shoot elongation than root and shoot amendment during the experiment period. The study demonstrated that A. adenophora extract and residue amendment have strong allelopathic effects on woody shrub species and indicating allelopathy played important role in the successful establishment and rapid spread of A. adenophora in the understory of chir pine forests.

An efficient micropropagation protocol for Ficus carica cv. Golden Orphan suitable for mass propagation

Fig ( Ficus carica L.) is from the Moraceae family and is rich in essential nutrients, natural fiber and vitamins. The Golden Orphan cultivar is a yellow fig that is sweet, firm and can thrive in tropical climates. Current conventional propagation methods for the multiplication of plant stocks were found to be less efficient in producing healthy plant stocks. Micropropagation offers an alternative in the production of plant stocks resembling the quality of mother plants. The current study aims to fine tune the micropropagation protocol of the Golden Orphan cultivar for efficient production of plant stocks. Sterile nodal bud explants were subjected to different media treatments, carbon source and combinations of auxin and cytokinin. Rooting of explants was induced in auxin and rooted explants were acclimatized in cocopeat. The optimal basal medium for shoot elongation was Murashige and Skoog (MS) Medium, whereas 20 g/L sucrose resulted in the highest shoot length (2.00 ± 0.22 cm) facilitating the production of nodal segments for subsequent multiplication. The highest shoot induction (4.15 ± 0.43 shoots/explant) was observed in the treatment of 0.8 mg/L 6-Benzylaminopurine (BAP), whereas the combination of 0.8 mg/L BAP and 0.5 mg/L indole-3-acetic acid (IAA) resulted in the highest shoot length (2.23 ± 0.09 cm). Treatment of 0.4 mg/L indole-3-butyric acid (IBA) produced the optimal percentage of rooting (83.33%) whereas acclimatization with cocopeat resulted in maximum survival rate. The present study has successfully optimised the crucial aspects of micropropagation for the Golden Orphan cultivar suitable for rapid plant stock production. • The establishment of micropropagation protocol for Ficus carica cv. Golden Orphan. • High multiplication rate in basal medium, minimal amount of sucrose and cytokinin. • Maximum acclimatization efficiency in cocopeat. • Acclimatized plants successfully produced fruits that resembles mother plants.

Uptake, translocation, phytotoxicity, and hormetic effects of titanium dioxide nanoparticles (TiO2NPs) in Nigella arvensis L.

The extensive application of titanium dioxide nanoparticles (TiO2NPs) in agro-industrial practices leads to their high accumulation in the environment or agricultural soils. However, their threshold and ecotoxicological impacts on plants are still poorly understood. In this study, the hormetic effects of TiO2NPs at a concentration range of 0–2500 mg/L on the growth, and biochemical and physiological behaviors of Nigella arvensis in a hydroponic system were examined for three weeks. The translocation of TiO2NPs in plant tissues was characterized through scanning and transmission electron microscopy (SEM and TEM). The bioaccumulation of total titanium (Ti) was quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Briefly, the elongation of roots and shoots and the total biomass growth were significantly promoted at 100 mg/L TiO2NPs. As the results indicated, TiO2NPs had a hormesis effect on the proline content, i.e., a stimulating effect at the low concentrations of 50 and 100 mg/L and an inhibiting effect in the highest concentration of 2500 mg/L. A biphasic dose-response was observed against TiO2NPs in shoot soluble sugar and protein contents. The inhibitory effects were detected at ≥1000 mg/L TiO2NPs, where the synthesis of chlorophylls and carotenoid was reduced. At 1000 mg/ L, TiO2NPs significantly promoted the cellular H2O2 generation, and increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Furthermore, it enhanced the total antioxidant content (TAC), total iridoid content (TIC), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. Overall, the study revealed the physiological and biochemical alterations in a medicinal plant affected by TiO2NPs, which can help to use these NPs beneficially by eliminating their harmful effects.

Transcriptomic and proteomic analyses of far-red light effects in inducing shoot elongation in the presence or absence of paclobutrazol in Chinese pine

Transcriptomic and proteomic analyses of far-red light effects in inducing shoot elongation in the presence or absence of paclobutrazol in Chinese pine

Irradiance-regulated biomass allocation in Raphanus sativus plants depends on gibberellin biosynthesis

Gibberellin has been proposed to increase leaf elongation in radish (Raphanus sativus L.) plants, which is associated with decreased tuber growth. Since light intensity can control growth through interaction with gibberellin, investigation of the effect of gibberellin levels on the growth of radish plants would be a step forward towards unraveling factors that underlie biomass accumulation and allocation in response to irradiance levels. Here, we report that the gibberellin biosynthesis inhibitor paclobutrazol (PAC) decreased petiole elongation, but not lamina growth of radish plants grown under full sunlight. However, shading promoted an increase in shoot elongation, while in plants treated with PAC the petiole and leaf lamina fail to elongate. Plants treated with PAC allocated proportionally more biomass to their tubers and less to shoot compared to control under shade. Moreover, PAC decreased the abundance of transcripts encoding cell wall expansion proteins in leaf lamina and petiole of plants grown under shade, which was positively correlated with sugar consumption by the tuber, thereby increasing the mass fraction and concentrations of minerals for tuber. Thus, allocation of biomass during the growth of radish plants and nutritional quality of tubers depend on gibberellin and light intensity.

Optimisation of micropropagation protocols for temperate eucalypt hybrids in South Africa, with a focus on auxin transport proteins

Globally the demand for forestry resources is booming, and consequently innovative approaches to cultivate valuable hardwoods, such as eucalypts, are crucial. Although micropropagation offers a means to clonally propagate desirable cultivars, this technique is often variety-specific for eucalypts. Thus, recalcitrant genotypes are often excluded from micropropagation programmes as development requires large investments of time, money and expertise. In this study, a minimal maintenance medium was developed to reduce subculturing frequency (∼8 days) and to evaluate each micropropagation stage independently. Furthermore, a generic protocol for use across different varieties was developed by assessing the in vitro performance of three different Eucalyptus grandis x Eucalyptus nitens varieties (varieties 1–3) across various treatments. The purpose of this protocol was to ease the in vitro establishment of novel eucalypt varieties by providing a foundation for future protocol optimisation. During multiplication, medium containing 0.5 mg l−1 meta-topolin with 0.1 mg l−1 of indole acetic acid (IAA) induced the highest bud proliferation and shoot elongation for varieties 1 (59.1 ± 2.9; 1.2 cm ± 0.08), 2 (62.3 ± 2.7; 1.5 cm ± 0.09) and 3 (58.1 ± 3; 1.2 cm ± 0.07). Following multiplication, the rooting treatment that achieved the most consistent rooting percentages among varieties 1 (33.4%), 2 (43.5%) and 3 (34.3%) incorporated 0.029 mg l−1 of racemic-GR24 with 0.5 mg l−1 of IAA. Additionally, root vigour was assessed by measuring the root number and length, which varied considerably based on the variety and treatment in question. Overall, variety 2 was the most amenable to plant growth regulators and upon further investigation was found to possess equal expression levels of the auxin transporters PIN1 and AUX1. Conversely, the other varieties displayed unequal ratios of these transporters. Considering that auxins are principal media components, these expression profiles may serve as markers to identify eucalypt cultivars amenable to micropropagation.

Higher stock plant nitrogen and phosphorus levels favor rooting on mini cuttings of tea tree

AbstractThe impact of N and P nutrition of stock plants of tea trees (Melaleuca alternifolia) on rooting and survival of cuttings was investigated in order to optimize adventitious rooting and growth of scion cuttings used for clonal propagation. High rates of 300 kg N ha–1 and 100 kg P ha–1 led to higher rooting, shoot elongation, and survival of the cuttings than low rates of 25 kg N ha–1 and 5 kg P ha–1, and are thus recommended for tea tree clonal propagation.

English

Jatropha is a drought-tolerant plant producing seed oil for the biodiesel. Limitation to the development of jatropha is unavailability of high-yielding varieties and efficient in vitro regeneration system which is required for micropropagation. In this study, in vitro regeneration system from jatropha juvenile cotyledon was established. Firstly, concentrations of hormones in the MS medium were optimized and it was found that 1.5 mgL-1 benzyl adenine (BA) + 0.05 mgL-1 indole-3-butyric acid (IBA) + 0.5 mgL-1 thidiazuron (TDZ) turned out to be the best for shoot induction (3.82 ± 0.18 shoots/explant). Secondly, shoot induction medium was fortified with different concentrations of glutamine and adenine sulfate. It was found that 25 mgL-1 each of glutamine and adenine sulfate was the most effective, resulting to 9.09 ± 0.37 shoots/explant and 93.0% regeneration frequency. Regenerated shoots were cultured on medium containing 0.5 mgL-1 BA and different concentrations of gibberellic acid (GA3), 0.5 mgL-1 GA3 with 0.5 mgL-1 BA  were found to be the best for shoot elongation (2.13 ± 0.18 cm). The highest frequency of root (40%) was observed on the medium with 0.5 mgL-1 IBA. The established procedures will be useful for the mass propagation and genetic transformation of elite jatropha genotypes.   Key words: Adenine sulfate (Ads), benzyl adenine (BA), indole-3-butyric acid (IBA), in vitro regeneration, glutamine (Gln).

Ethylene Acts as a Negative Regulator of the Stem-Bending Mechanism of Different Cut Snapdragon Cultivars.

This study investigated whether ethylene is involved in the stem-bending mechanism of three different snapdragon cultivars ‘Asrit Red’, ‘Asrit Yellow’, and ‘Merryred Pink’, by treating their cut stems with an ethylene-releasing compound (ethephon), an ethylene-action inhibitor [silver thiosulfate (STS)], and distilled water (as the control). Ethephon completely prevented stem bending in all cultivars, whereas STS exhibited a higher bending rate compared with the control. The bending rates were influenced by several factors, such as the degree of stem curvature, relative shoot elongation, ethylene production, and lignin content, indicating their involvement in the stem-bending mechanism of the cultivars. The analysis of the expression of genes involved in the ethylene and lignin biosynthetic pathways also supported the importance of lignin and ethylene in the stem-bending mechanism. Taken together, as ethephon completely prevented stem bending of the three snapdragon cultivars, this study suggested that ethylene acts as a negative regulator of the stem-bending mechanism of snapdragon cultivars, and the information will be valuable for the prevention of stem bending in other commercially important ornamental flowers.

Relative morpho-physiological responses of millets and oats against lead toxicity

Lead (Pb) toxicity due to accumulation in pearl millet (Pennisetum glaucum (L.) R. Br.), finger millet (Eleusine coracana (L.) Gaertn.) and oat (Avena sativa L.) was investigated. Seeds were grown on MS medium supplemented with 0–40 mg/l Pb and their response was noted after 15 days of germination. Accumulation of Pb in all the 3 species increased with increasing Pb, and maximum accumulation (91.3 ± 1.8 mg/l) was noted in roots of finger millet at 40 mg/l Pb. Toxicity effect of Pb accumulation was determined in terms of seed germination, seedling growth, chlorophyll and proline content, and antioxidative activity. Maximum decline in seed germination (78.5 %) was noted in oats. Inhibition of shoot (∼75–78.3 %) and root (∼97–98 %) elongation was maximum in pearl millet and oat, while reduction in biomass accumulation was maximum in shoot (67 %) and root (∼74 %) in oat. Chlorophyll content decreased significantly and was minimum (1.01 ± 0.03 mg/g FW) in pearl millet at 40 mg/l Pb. Higher SOD and GPX activities were noted in all the plantlets, while CAT activity decreased with increasing Pb levels in the medium. At the highest Pb concentration, proline accumulation (13.1 ± 0.17 μM/g FW), MDA content (22.1 ± 0.20 μmol/g FW), SOD activity (58.73 ± 0.69 U/mg protein) and GPX activity (1.5 ± 0.01 U/g FW) were maximum in oat roots, while CAT activity (75.03 ± 2.37 mg H2O2 destroyed/5 min/g FW) was maximum in shoots of finger millet. Finger millet was more tolerant to Pb toxicity and showed significant accumulation potential in both above and below ground parts. This study provides an overview of toxicity and tolerance mechanism of millets and oats against Pb stress. The study helps in understanding the mechanism of detoxification of lead employed by the plants and to select tolerant plant variety which could be used to bioremediate the lead contaminated soils.

Phenology explains different storage remobilization in two congeneric temperate tree species with contrasting leaf habit

The dependence of trees on carbon and nutrient storage is critical to predicting the forest vulnerability under climate change, but whether evergreen and deciduous species differ in their use and allocation of stored resources during spring phenology is unclear. Using a high temporal resolution, we evaluated the role of spring phenology and shoot growth as determinants of the carbon and nutrient storage dynamics in contrasting leaf habits. We recorded the phenology and shoot elongation and determined the concentrations of total non-structural carbohydrates (NSCs), starch, soluble carbohydrates, nitrogen (N) and phosphorus (P) in buds, expanding shoots and previously formed shoots of two sympatric Nothofagus species with contrasting leaf habit. Species reached similar shoot lengths, though shoot expansion started 35 days earlier and lasted c. 40 days more in the deciduous species. Thus, although the deciduous species had a relatively constant shoot growth rate, the evergreen species experienced a conspicuous growth peak for c. 20 days. In the evergreen species, the greatest decreases in NSC concentrations of previously formed shoots and leaves coincided with the maximum shoot expansion rate and fruit filling, with minimums of 63 and 65% relative to values at bud dormancy, respectively. In contrast, minimum NSC concentrations of the previously formed shoots of the deciduous species were only 73% and occurred prior to the initiation of shoot expansion. Bud N and P concentrations increased during budbreak, whereas previously formed shoots generally did not decrease their nutrient concentrations. Late spring phenology and overlapping of phenophases contributed to the greater dependence on storage of proximal tissues in the studied evergreen compared with deciduous species, suggesting that phenology is a key determinant of the contrasting patterns of storage use in evergreen and deciduous species.

A robust in-vitro protocol for shoot multiplication of Echinacea angustifolia

Echinacea angustifolia is an important medicinal and ornamental plant found in various regions of the world. This species may become threatened due to over-exploitation for medicinal uses. The present study was carried out to develop a rapid in vitro multiplication protocol using explants raised from seedlings. Complete plantlets have been successfully regenerated from shoot tip, leaf, petiole, stem, and root explants. The explants were incubated on Murashige and Skoog (MS) culture medium supplemented with different combinations of 6-benzyl amino purine (BAP) naphthalene acetic acid (NAA). Multiplication of shoot tips was achieved on BAP while from other explants; multiple shoots were regenerated on MS medium supplemented with BAP and NAA. The response of growth regulators was investigated. The shoot tip explants showed the highest rate of shoot induction (80%) and a shoot regenerated about 25 shoots per explants when cultured on MS media supplemented with BAP (4 µM) within 6–7 weeks. The leaf explants also developed shoots and each shoot generated 15 shoots in MS medium supplemented with BAP (5 µM) and NAA (5 µM). Shoot regeneration was also achieved with other explants mainly root, petiole, and stem on MS medium containing BAP (5 µM) + NAA (5 µM). The multiple elongated shoots were obtained on MS basal medium. Well-developed roots were achieved on MS medium in combination with BAP and NAA and 80% of plantlets were survived in the soil successfully in the hardening process. A robust and optimized protocol will be helpful for the mass production of this medicinal plant.

Effects of BrMYC2/3/4 on Plant Development, Glucosinolate Metabolism, and Sclerotinia sclerotiorum Resistance in Transgenic Arabidopsis thaliana.

MYC2/3/4, known as a basic helix–loop–helix (bHLH) transcription factor, directly activate the genes involved in diverse plant development and secondary metabolites biosynthesis. In this study, we identified and cloned five MYC paralogs (BrMYC2/3-1/3-2/4-1/4-2) from Chinese cabbage (Brassica rapa ssp. pekinensis). In-silico analyses for the physicochemical properties suggested that BrMYC2/3-1/3-2/4-2/4-3 are unstable hydrophobic and acidic proteins, while BrMYC4-1 is an unstable hydrophobic and basic protein. BrMYC2/3/4 belong to the bHLH superfamily and are closely related to AthMYC2/3/4 orthologs that mediate the regulation of various secondary metabolites. It was demonstrated that BrMYC2/3/4-GFP fusion protein localized in the nucleus and expression levels of five BrMYC2/3/4 homologous genes all elevated relative to control (Ctrl). When expressed in Arabidopsis under the control of 35S promoter, each of the BrMYC2/3-1/3-2/4-1/4-2 transgenes differentially influenced root and shoot elongation, vegetative phase change, flowering time, plant height and tiller number after flowering, and seed production. Despite the variation of phenotypes between the transgenic lines, all the lines except for BrMYC4-2 exhibited shorter seed length, less seed weight, higher accumulation of glucosinolates (GSs), and resistance to Sclerotinia sclerotiorum than Ctrl. Notably, BrMYC2 overexpression (OE) line significantly reduced the lengths of root and hypocotyl, seed length, and weight, along with faster bolting time and strikingly higher accumulation of total GSs. Accumulation of GSs at the highest levels in the BrMYC2OE line conferred the highest resistance to S. sclerotiorum. Unlike BrMYC3OE and BrMYC4OE, BrMYC2OE stimulated the growth of plant height after fluorescence. The results of this study point to the BrMYC2 overexpression that may provide a beneficial effect on plant growth and development via plant resistance to the fungal pathogen.

Starve to Sustain-An Ancient Syrian Landrace of Sorghum as Tool for Phosphorous Bio-Economy?

Phosphorus (P) is an essential macronutrient, playing a role in developmental and metabolic processes in plants. To understand the local and systemic responses of sorghum to inorganic phosphorus (Pi) starvation and the potential of straw and ash for reutilisation in agriculture, we compared two grain (Razinieh) and sweet (Della) sorghum varieties with respect to their morpho-physiological and molecular responses. We found that Pi starvation increased the elongation of primary roots, the formation of lateral roots, and the accumulation of anthocyanin. In Razinieh, lateral roots were promoted to a higher extent, correlated with a higher expression of SbPht1 phosphate transporters. Infrared spectra of straw from mature plants raised to maturity showed two prominent bands at 1371 and 2337 cm−1, which could be assigned to P-H(H2) stretching vibration in phosphine acid and phosphinothious acid, and their derivates, whose abundance correlated with phosphate uptake of the source plant and genotype (with a higher intensity in Razinieh). The ash generated from these straws stimulated the shoot elongation and root development of the rice seedlings, especially for the material derived from Razinieh raised under Pi starvation. In conclusion, sorghum growing on marginal lands has potential as a bio-economy alternative for mineral phosphorus recycling.

Response of Merlot Grapevine to Drought Is Associated to Adjustments of Growth and Nonstructural Carbohydrates Allocation in above and Underground Organs

Studying changes in partitioning of dry matter and nonstructural carbohydrates (NSC) content in both aboveground and underground perennial tissues in drought-affected grapevines could provide insights into plant response and carbon allocation strategies during stress periods. The analysis of soluble NSC and starch content in leaf petioles, due to their role in hydraulic segmentation, should also be considered. In the present research, these aspects have been investigated in Merlot grapevines grown in pots and subjected to progressive and increasing soil dehydration, and in well-irrigated vines. Drought conditions caused drastic reduction of shoot elongation and total plant leaf area development in favor of a greater biomass allocation and partitioning towards roots, where most of the NSC reserves were also conserved. Dry matter content of the perennial organs increased in stressed vines due to growth reduction, allocation of carbon reserves and possible anatomical modifications. Vines subjected to drought showed a higher NSC content in petioles, supporting the hypothesis that they are involved as compatible solutes in osmotic adjustments.

Phytoaccumulation potential and enzymatic activities of Oryza sativa L. genotypes exposed to Cr (VI) in hydroponic culture

In this work, the phytoaccumulation efficiency and enzymatic activities of various rice (Oryza sativa L.) genotypes exposed to differential concentrations of Cr (VI) have been studied. The cultivars experimented were Pratikshya, Sankar, Annapurna, White swarna and Pimpudibasa. The seedlings were raised with ¼ strength Hoagland’s nutrient solution prepared in deionised water supplemented with different concentrations (0, 100, 200, 300 and 400µg/L) of hexavalent Cr as potassium dichromate (K2Cr2O7) under controlled environmental conditions. The seedlings were harvested at 7 days intervals and parameters like root and shoot elongation, enzymatic activities and tolerance to chromium ions were measured after different periods of exposure. The highest concentration of Cr (VI) ions in shoots (9.92 µg/g dry weight) and roots (8.51µg/g dry weight) was found in Pratikshya exposed to 300 µg/L of Cr(VI) after 21 days of treatments. The growth parameters of five cultivars and tolerance to chromium were in the order of Pratikshya>Sankar>Annapurna>White swarna>Pimpudibasa. Cr(VI) toxicity was correlated with peroxidase and catalase enzyme activities of different rice cultivars. The interaction between chromium ions and rice cultivars biomass was studied using SEM-EDX and FTIR analysis.