Remediation of salt-affected soil by the addition of organic matter: an investigation into improving glutinous rice productivity

Soil salinity may limit plant growth and development, and cause yield loss in crop species. This study aimed at remediating saline soil using organic matter (OM) treatment, before the cultivation of RD6 rice (Oryza sativa L. spp. indica). Physiological and morphological characters of rice plants, as well as crop yield, were evaluated from salt-affected soil with varying levels of salinity. The chlorophyll a and total chlorophyll pigments of rice plants grown in salt-affected soil (2% salt level) with the application of OM were maintained better than in plants grown without OM treatment. The degree of reduced photosynthetic pigments in rice plants was dependent on the level of salt contamination. Pigment content was positively related to maximum quantum yield of PSII (Fv/Fm) and quantum efficiency of PSII (ΦPSII), leading to reduced net photosynthetic rate (Pn) and reduced total grain weight (TGW). Photosynthetic abilities, including chlorophyll a and total chlorophyll pigments and ΦPSII, in rice plants grown with OM treatment were greater than in those cultivated in soil without the OM treatment, especially in high salt levels (1-2% salt). The remediation of salt-affected soil in paddy fields using OM should be applied further, as an effective way of enhancing food crop productivity

Osmotic potential, photosynthetic abilities and growth characters of oil palm (Elaeis guineensis Jacq.) seedlings in responses to polyethylene glycol-induced water deficit

The aim of the present study is to investigate the biochemical, physiological and morphological responses of oil palm seedlings when exposed to polyethylene glycol (PEG)-induced water deficit. Oil palm seedlings were photo-autotrophically grown in MS media and subsequently exposed to -0.23 (control), -0.42, -0.98 or -2.15 MPa PEG-induced water deficit. Osmotic potential (Ψs) in root and leaf tissues of oil palm seedlings grown under PEG-induced water deficit was decreased leading to chlorophyll degradation. Chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (TC), total carotenoids (Cx+c), maximum quantum yield of photosystem II (PSII) (Fv/Fm) and photon yield of PSII (ΦPSII) in the oil palm seedlings under water deficit conditions dropped significantly in comparison to the control group, leading to a reduction in net-photosynthetic rate (Pn) and growth. A positive correlation between physiological and growth parameters, including osmotic potential, photosynthetic pigments and water oxidation in photosystem II and Pn was demonstrated. These data provide the basis for the establishment of multivariate criteria for water deficit tolerance screening in oil palm breeding programs.Key words: Chlorophyll fluorescence, net-photosynthetic rate, pigment, water oxidation, water deficit stress

Screening upland rice (Oryza sativa L. ssp. indica) genotypes for salt-tolerance using multivariate cluster analysis

Seedlings of thirteen genotypes of rice were photoautotrophically grown on MS medium and subsequently exposed to 0 (control) or 200 mM NaCl (salt stress) for 14 days. Chlorophyll a (Chla), chlorophyll b (Chlb) and total carotenoids (Cx+c), in the salt stressed leaves of all genotypes decreasedsignificantly, but the extent of the decrease varied among different genotypes. Maximum quantum yield of photosystem II (PSII) (Fv/Fm), photon yield of PSII (FPSII) and net photosynthetic rate (Pn) in saltstressed seedlings of all genotypes dropped significantly, whereas FPSII in cv. Homjan (HJ), Dokpayom (DPY), Chewmaejan 2 (CMJ2) and upland rice 1 (UR1) were alleviated. Moreover, growth parameters including shoot height, root length, fresh weight, dry weight and leaf area in salt stressed plantlets of all genotypes were significantly inhibited. The pigment degradation, photosynthetic abilities and growth inhibition in saline regimes were subjected to hierarchical cluster analysis, which lead to theclassification of Kumuangluang (KML), Khao Dawk Mali (KDML), Pokkali (POK), HJ, DPY, Chewmaejan 1 (CMJ1), CMJ2, UR1 and Chowho (CH) as salt tolerant and R258, Pathumthani 1 (PT1), IR29 and upland rice 2 (UR2) as salt sensitive

Salt stress induced ion accumulation, ion homeostasis, membrane injury and sugar contents in salt-sensitive rice (Oryza sativa L. spp. indica) roots under isoosmotic conditions

Excess salt induced ionic and osmotic stresses that disturbed metabolism and led to reduction of plant development. Previous studies reported that sugars in stressed plants were involved in stress tolerance. However, the role of sugars in salt-stressed plants against only ionic effects is still unclear. The objective of this research was to investigate accumulation and homeostasis of ions, membrane injury, water content, growth characters and sugar contents in roots, in-response to salt stress under iso-osmotic conditions. Salt-sensitive rice, Pathumthani1 (PT1) was grown on MS culture medium for 7 days and was adjusted to salt stress under iso-osmotic conditions (-1.75 ± 0.20 MPa) by mannitol for 4 days. An increase in NaCl increased Na+ and Na+:K+ in PT1 roots leading to increased membrane injury, while the water content was decreased. Additionally, growth characters, including number, length, fresh weight and dry weight of roots, were inhibited. Sugar accumulations in PT1 roots were enhanced by increases in NaCl. The increase in Na+ was positively related to total soluble sugars, resulting in an osmotic adjustment of the membrane that maintained water availability. The accumulation of sugars in PT1 roots may be a primary salt-defense mechanism and may function as an osmotic control.Key words: Mannitol, membrane injury, oligosaccharides, sodium ion, potassium ion, sodium chloride

Gamma Irradiation Causes Variation and Stability of Artemisinin Content in <em>Artemisia annua</em> Plants

Artemisinin is an anti-malarial sesquiterpene lactone isolated from Artemisia annua L., a traditional Chinese herb of the family Asteraceae. The plant contains relatively low artemisinin content, ranging from 0.01 to 0.8% of the plant dry weight, depending on the geographical origin, seasonal, and somatic variations. Ionizing radiation has been recognized as a powerful technique for plant improvement, especially in crop plants. This technique creates genetic variability in plants, which can be screened for desirable characteristics. Very little is known about the effect of gamma irradiation on the potential increase of artemisinin production in A. annua. In this study, 130 shoot tips excised from the population of in vitro A. annua plantlets (with an average leaf artemisinin content of 0.18 ± 0.09%) were exposed to 5 Gy 60Co gamma irradiation and subsequently transferred to a suitable medium for in vitro development of plantlets. The resulting 90 stable survived after four passages appeared to have a wide variation of artemisinin content, ranging from 0.02 to 0.68% of dry weight. All the viable plantlets were then transferred from the in vitro cultures to ex vitro conditions both in a greenhouse and an open field. A significant correlation was observed between artemisinin content among individual pairs of the vitro plantlets and ex vitro mature plants, with the correlation coefficient (R2) values of 0.915 for the greenhouse plants and 0.797 for the open field plants. Among these, the highest artemisinin-containing plant appeared to accumulate 0.84% artemisinin of dry weight in the open field, which is almost five times higher than the original plants. These results suggest that gamma irradiation with 5-Gy dose can produce viable variants of A. annua that can maintain the biosynthetic capability of artemisinin throughout the in vitro-ex vitro transfer and development of the first generation of mature plants

A highly efficient method for Agrobacterium mediated transformation in elite rice varieties (Oryza sativa L. spp. indica)

An Agrobacterium mediated transformation method was developed for the Thai rice variety,  Pathumthani 1 (PT1), and the Indian rice variety, Pokkali (PKL). Various aspects of the transformation method, including callus induction, callus age, Agrobacterium concentration and co-cultivation period were examined, in order to improve transformation efficiency. Optimized transformation conditions were established using Agrobacterium strain EHA105, which carries a virulent plasmid, pCAMBIA1301.  A modified Murashige and Skoog (MS) medium supplemented with 1 mg/l 2, 4-D and 0.5 mg/l picloram was optimized for callus induction. Three week old calli were used to co-cultivate with 0.8 -1 OD600  Agrobacterium for 30 min and the culture was continued on agar medium without antibiotics for 2 days. This method can be used to induce high quality calli within three weeks. Based on GUS determination, it was demonstrated that the transformation method was improved significantly, with a high level of transformation efficiency.Keywords: Agrobacterium tumefaciens, indica rice, mature seed-derived callus, rice transformation, transgenic riceAfrican Journal of Biotechnology Vol. 9(34), pp. 5488-5495, 23 August, 201

Field Screening of Sugarcane (Saccharum spp.) Mutant and Commercial Genotypes for Salt Tolerance

Growth and physiological attributes and sugar quality parameters are considered key criteria for screening sugarcane cultivars for salt tolerance. Maximum cane growth and yield were found in a positive check (‘K88-92’) as well as in cv. ‘(A3)AE1-18’ when subjected to salt affected soil. Percent reduction in Fv/Fm, quantum efficiency of PSII (ΦPSII) and water use efficiency (WUE) due to salt stress was considerably low in ‘K88-92’, ‘(A3)AE1-18’ and ‘KK3’ which was associated with very low salt-induced reduction in net photosynthetic rate and growth characters such as shoot length, number of internodes, and internodal length as well as yield traits. In addition, brix, polarlization, fiber, purity and commercial cane sugar (CCS) in ‘(A18)AE2-15’ and ‘(A3)AE1-18’ were well maintained under saline stress. By subjecting the data for various physiological, growth, yield and sugar quality parameters to the Ward’s cluster analysis ‘K88-92’ (positive check), ‘(A3)AE1-18’ and ‘KK3’ were identified as salt tolerant, whereas ‘(A11)AE1-114’ and ‘K97-32’ as salt sensitive

Remediation of salt-affected soil by the addition of organic matter: an investigation into improving glutinous rice productivity

Soil salinity may limit plant growth and development, and cause yield loss in crop species. This study aimed at remediating saline soil using organic matter (OM) treatment, before the cultivation of RD6 rice (Oryza sativa L. spp. indica). Physiological and morphological characters of rice plants, as well as crop yield, were evaluated from salt-affected soil with varying levels of salinity. The chlorophyll a and total chlorophyll pigments of rice plants grown in salt-affected soil (2% salt level) with the application of OM were maintained better than in plants grown without OM treatment. The degree of reduced photosynthetic pigments in rice plants was dependent on the level of salt contamination. Pigment content was positively related to maximum quantum yield of PSII (Fv/Fm) and quantum efficiency of PSII (&#934;PSII), leading to reduced net photosynthetic rate (Pn) and reduced total grain weight (TGW). Photosynthetic abilities, including chlorophyll a and total chlorophyll pigments and &#934;PSII, in rice plants grown with OM treatment were greater than in those cultivated in soil without the OM treatment, especially in high salt levels (1-2% salt). The remediation of salt-affected soil in paddy fields using OM should be applied further, as an effective way of enhancing food crop productivity

Effect of photosynthetic photon flux density on growth, photosynthetic competence and antioxidant enzymes activity during ex vitro acclimatization of Dieffenbachia cultivars

The effects of 35, 70 and 100 µmol m−2 s−1 photosynthetic photon flux density (PPFD) were investigated on ex vitro acclimatization of micropropagated Dieffenbachia plants. Various growth characteristics, photosynthetic parameters and activities of antioxidant enzymes and dehydrins (DHN) were investigated. Fresh and dry plant biomass, plant height and root length were highest under the highest PPFD (100 µmol m−2 s−1), but this treatment was responsible for a reduction in the number of leaves. Chlorophyll and carotenoid contents and net photosynthesis were also optimal in plants grown under the highest irradiance. Stomatal resistance, transpiration rate and Fv/Fm values decreased with the incremental light irradiance. Activities of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase were higher in the plants treated with 70 and 100 µmol m−2 s−1 PPFD. Accumulation of 55 kDa, 40 and 22 kDa DHN was observed in all light treatments. These results depict that lower PPFD (35 µmol m−2 s−1) was suitable for acclimatization of Dieffenbachia plants. High PPFD (>70 µmol m−2 s−1) induced accumulation of antioxidants and accumulation of DHN in the plants which reveals enhanced stress levels

Porcentaje de supervivencia, capacidad fotosintética y crecimiento de dos cultivares de arroz tipo índica (Oryza sativa L. spp. indica) en respuesta al estrés iso-osmótico

The aim of this study was to investigate pigment degradation, chlorophyll fluorescence diminution, photosynthetic ability and growth reduction in two rice cultivars, in response to either iso-osmotic salt stress or water-deficit stress. Seedlings of rice cultivars RD6 and KDML105 were photo-autotrophically grown in MS media and subsequently exposed to –0.23 (control), –0.40 or –0.67 MPa iso-osmotic NaCl (salt stress) or mannitol (water-deficit stress) for 14 days. The survival percentage of the two rice cultivars reduced dramatically when subjected to –0.67 MPa NaCl treatment. Chlorophyll a (Chla), chlorophyll b (Chlb), total carotenoids (Cx+c), maximum quantum yield of PSII (Fv/Fm) and photon yield of PSII (ΦPSII) in the stressed seedlings were significantly lower when compared to seedlings in the control group (without mannitol or NaCl), leading to low net-photosynthetic rate (Pn) and growth reduction. In addition, the growth characters of plantlets in the salt stress conditions were more sharply reduced, and the physiological changes greater than those in water-deficit stress conditions. On the other hand, non-photochemical quenching in the leaves of stressed plantlets increased significantly, especially in response to iso-osmotic salt stress. In the present study, overall growth performance and physiological characters of KDML105 grown under iso-osmotic stress were better than those of RD6.El objetivo de este estudio fue investigar la degradaci&oacute;n de pigmentos, la disminuci&oacute;n de la fluorescencia de la clorofila, la capacidad fotosint&eacute;tica y la reducci&oacute;n en el crecimiento de dos cultivares de arroz, en respuesta al estr&eacute;s salino iso-osm&oacute;tico o h&iacute;drico. Se cultivaron de forma foto-autotr&oacute;fica en medio MS pl&aacute;ntulas de los cultivares RD6 y KDML105 y posteriormente se expusieron durante 14 d&iacute;as a NaCl (estr&eacute;s salino) o manitol (estr&eacute;s h&iacute;drico) iso-osm&oacute;tico &ndash;0,23 (control), &ndash;0,40 &oacute; &ndash;0,67 MPa. El porcentaje de supervivencia de los dos cultivares de arroz se redujo dr&aacute;sticamente con el tratamiento de NaCl 0,67 MPa. La clorofila a (Chla), clorofila b (Chlb), carotenoides totales (Cx+c), rendimiento cu&aacute;ntico m&aacute;ximo del PSII (Fv/Fm) y el rendimiento de fotones del PSII (&Phi;PSII) fueron significativamente menores en las pl&aacute;ntulas estresadas respecto a las pl&aacute;ntulas del grupo control (sin manitol o NaCl), lo que les llev&oacute; a una baja tasa de fotos&iacute;ntesis neta (Pn) y a una reducci&oacute;n del crecimiento. Adem&aacute;s, el crecimiento de las pl&aacute;ntulas bajo estr&eacute;s salino se redujo dr&aacute;sticamente y los cambios fisiol&oacute;gicos fueron mayores que bajo estr&eacute;s h&iacute;drico. Por otra parte, el amortiguamiento no fotoqu&iacute;mico (NPQ) en las hojas de las pl&aacute;ntulas estresadas aument&oacute; considerablemente, especialmente en respuesta al estr&eacute;s salino iso-osm&oacute;tico. En este estudio, los caracteres de crecimiento y fisiol&oacute;gicos en conjunto de KDML105 cultivados bajo estr&eacute;s iso-osm&oacute;tico fueron mejores que los de RD6