Thapanee Samphumphuang

Physio-biochemical and morphological characters of halophyte legume shrub, Acacia ampliceps seedlings in response to salt stress under greenhouse

Acacia ampliceps (salt wattle), a leguminous shrub, has been introduced in salt-affected areas in the northeast of Thailand for the remediation of saline soils. However, the defense mechanisms underlying salt tolerance A. ampliceps are unknown. We investigated various physio-biochemical and morphological attributes of A. ampliceps in response to varying levels of salt treatment (200–600 mM NaCl). Seedlings of A. ampliceps (25 ± 2 cm in plant height) raised from seeds were treated with 200 mM (mild stress), 400 and 600 mM (extreme stress) of salt treatment (NaCl) under greenhouse conditions. Na+ and Ca2+ contents in the leaf tissues increased significantly under salt treatment, whereas K+ content declined in salt-stressed plants. Free proline and soluble sugar contents in plants grown under extreme salt stress (600 mM NaCl) for 9 days significantly increased by 28.7 (53.33 μmol g–1 FW) and 3.2 (42.11 mg g–1 DW) folds, respectively over the control, thereby playing a major role as osmotic adjustment. Na+ enrichment in the phyllode tissues of salt-stressed seedlings positively related to total chlorophyll (TC) degradation (R2 = 0.72). Photosynthetic pigments and chlorophyll fluorescence in salt-stressed plants increased under mild salt stress (200 mM NaCl). However, these declined under high levels of salinity (400–600 mM NaCl), consequently resulting in a reduced net photosynthetic rate (R2 = 0.81) and plant dry weight (R2 = 0.91). The study concludes that A. ampliceps has an osmotic adjustment and Na+ compartmentation as effective salt defense mechanisms, and thus it could be an excellent species to grow in salt-affected soils.

Water-Deficit Tolerance in Sweet Potato [Ipomoea batatas (L.) Lam.] by Foliar Application of Paclobutrazol: Role of Soluble Sugar and Free Proline

The objective of this study was to elevate water deficit tolerance by improving soluble sugar and free proline accumulation, photosynthetic pigment stabilization, photosynthetic abilities, growth performance and storage root yield in sweet potato cv. ‘Tainung 57’ using a foliar application of paclobutrazol (PBZ). The experiment followed a Completely Randomized Block Design with four concentrations of PBZ: 0 (control), 17, 34, and 51 μM before exposure to 47.5% (well irrigation), 32.3% (mild water deficit) or 17.5% (severe water deficit) soil water content. A sweet potato cultivar, ‘Japanese Yellow’, with water deficit tolerance attributes was the positive check in this study. Total soluble sugar content (sucrose, glucose, and fructose) increased by 3.96-folds in ‘Tainung 57’ plants treated with 34 μM PBZ grown under 32.3% soil water content (SWC) compared to the untreated plants, adjusting osmotic potential in the leaves and controlling stomatal closure (represented by stomatal conductance and transpiration rate). In addition, under the same treatment, free proline content (2.15 μmol g-1 FW) increased by 3.84-folds when exposed to 17.5% SWC. PBZ had an improved effect on leaf size, vine length, photosynthetic pigment stability, chlorophyll fluorescence, and net photosynthetic rate; hence, delaying wilting symptoms and maintaining storage root yield (26.93 g plant-1) at the harvesting stage. A positive relationship between photon yield of PSII (ΦPSII) and net photosynthetic rate was demonstrated (r2 = 0.73). The study concludes that soluble sugar and free proline enrichment in PBZ-pretreated plants may play a critical role as major osmoprotectant to control leaf osmotic potential and stomatal closure when plants were subjected to low soil water content, therefore, maintaining the physiological and morphological characters as well as storage root yield.

CPPU elevates photosynthetic abilities, growth performances and yield traits in salt stressed rice (Oryza sativa L. spp. indica) via free proline and sugar accumulation.

Application of N-2-(chloro-4-pyridyl)-N-phenyl urea (CPPU) to salt susceptible cultivar of indica rice (cv. PTT1) effected on free proline and soluble sugar accumulation and regulated the physio-morphological responses when subjected to salt stress condition was firstly demonstrated in this study. Soluble sugars, including sucrose, glucose and fructose, in leaf blade and leaf sheath were enriched in 0.1 mM CPPU pretreated plants subsequently exposed to 16.6 dS m(-1) NaCl for 10 days. In the long period (15 days) salt stress, free proline content in the leaf blade and leaf sheath were evidently peaked to act as osmotic adjustment in the salt-stressed plants. In addition, the photosynthetic pigments, including chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids, were maintained by the functional regulation of soluble sugar and free proline in the cellular levels, thereby leading to higher net photosynthetic rate. Further, the stomatal closure and transpiration rate in CPPU pretreated plants were retained under salt stress, thereby resulting in alleviation of growth performance and yield traits. This study suggested that exogenous application of CPPU may alternatively play effective role to improve the salt tolerant abilities of salt susceptible rice crop.

Regulation of anthocyanin accumulation in rice (Oryza sativa L. subsp. indica) using MgSO4 spraying and low temperature

ABSTRACT Pericarp pigmented grains of rice have been reported as anthocyanin enriched source of antioxidants. The aim of this investigation was to regulate anthocyanin accumulation in pericarp pigmented rice cv. ‘Hom Nil’ using 0, 10, 50, and 100 mM MgSO4 foliar spray. The level of magnesium content in the leaf tissues treated with 100 mM MgSO4 for 2 d increased 2.6 times over control (0 mM MgSO4). After growing the treated plants under 16°C for 28 d, photosynthetic abilities were reduced by 17−93%, leading to retarded plant height (39−42% less than control). In addition, grain yield per panicle of the plants grown under 16°C for 28 d was reduced by 26−75% compared to the plants grown under 32°C.Total anthocyanin concentration, cyanidin-3-glucoside and peonidin-3-glucoside in the pericarp of the grains derived from the rice treated with 100 mM MgSO4 was increased 3.8 times over the control. Peonidin-3-glucoside, a dominant compound was reported for the first time. The study concludes that Mg−enrichment may play a key role as a metalloid in stabilizing anthocyanin, a secondary metabolite in the leaf sheath tissues and pericarp of grains in ‘Hom Nil’ rice cultivar.