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

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 degradación de pigmentos, la disminución de la fluorescencia de la clorofila, la capacidad fotosintética y la reducción en el crecimiento de dos cultivares de arroz, en respuesta al estrés salino iso-osmótico o hídrico. Se cultivaron de forma foto-autotrófica en medio MS plántulas de los cultivares RD6 y KDML105 y posteriormente se expusieron durante 14 días a NaCl (estrés salino) o manitol (estrés hídrico) iso-osmótico –0,23 (control), –0,40 ó –0,67 MPa. El porcentaje de supervivencia de los dos cultivares de arroz se redujo drásticamente con el tratamiento de NaCl 0,67 MPa. La clorofila a (Chla), clorofila b (Chlb), carotenoides totales (Cx+c), rendimiento cuántico máximo del PSII (Fv/Fm) y el rendimiento de fotones del PSII (ΦPSII) fueron significativamente menores en las plántulas estresadas respecto a las plántulas del grupo control (sin manitol o NaCl), lo que les llevó a una baja tasa de fotosíntesis neta (Pn) y a una reducción del crecimiento. Además, el crecimiento de las plántulas bajo estrés salino se redujo drásticamente y los cambios fisiológicos fueron mayores que bajo estrés hídrico. Por otra parte, el amortiguamiento no fotoquímico (NPQ) en las hojas de las plántulas estresadas aumentó considerablemente, especialmente en respuesta al estrés salino iso-osmótico. En este estudio, los caracteres de crecimiento y fisiológicos en conjunto de KDML105 cultivados bajo estrés iso-osmótico fueron mejores que los de RD6

Survival percentage, photosynthetic abilities and growth characters of two indica rice (Oryza sativa L. spp. indica) cultivars in response to iso-osmotic stress

El objetivo de este estudio fue investigar la degradacion de pigmentos, la disminucion de la fluorescencia de la clorofila, la capacidad fotosintetica y la reduccion en el crecimiento de dos cultivares de arroz, en respuesta al estres salino iso-osmotico o hidrico. Se cultivaron de forma foto-autotrofica en medio MS plantulas de los cultivares RD6 y KDML105 y posteriormente se expusieron durante 14 dias a NaCl (estres salino) o manitol (estres hidrico) iso-osmotico .0,23 (control), .0,40 o .0,67 MPa. El porcentaje de supervivencia de los dos cultivares de arroz se redujo drasticamente con el tratamiento de NaCl 0,67 MPa. La clorofila a (Chla), clorofila b (Chlb), carotenoides totales (Cx+c), rendimiento cuantico maximo del PSII (Fv/Fm) y el rendimiento de fotones del PSII (�³PSII) fueron significativamente menores en las plantulas estresadas respecto a las plantulas del grupo control (sin manitol o NaCl), lo que les llevo a una baja tasa de fotosintesis neta (Pn) y a una reduccion del crecimiento. Ademas, el crecimiento de las plantulas bajo estres salino se redujo drasticamente y los cambios fisiologicos fueron mayores que bajo estres hidrico. Por otra parte, el amortiguamiento no fotoquimico (NPQ) en las hojas de las plantulas estresadas aumento considerablemente, especialmente en respuesta al estres salino iso-osmotico. En este estudio, los caracteres de crecimiento y fisiologicos en conjunto de KDML105 cultivados bajo estres iso-osmotico fueron mejores que los de RD6.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 (ÖPSII) 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