Induced Water Deficit Research Articles

Methodological approaches in the study of hydric stress in plants

Drought significantly affects plant growth and development, having a negative impact on the productivity of crops and, respectively, on food security worldwide. To predict the response of agricultural crops to future global warming and water deficit and to develop effective risk management strategies, there is a need to understand, at various levels of organization, the processes that determine tolerance to adverse environments. In this context it is important to use appropriate models of hydric stress induction and response assessment. The paper presents a brief description of the methodological approaches used in plant drought stress studies (field, greenhouse, laboratory experiments; experimental models using different types of substrates; distinct methods to induce water deficit), reflects their particularities, advantages and limitations and highlights the importance of combining and adapting methods of analysis according to the studied species, the environment and the research objectives.

Induced Water Deficit Tolerance in Hexaploid Wheat through Exogenous Application of Trehalose and Cytokinins: Water Relations and Physiological Changes

Induced Water Deficit Tolerance in Hexaploid Wheat through Exogenous Application of Trehalose and Cytokinins: Water Relations and Physiological Changes

Effects of Selenium on DNA Methylation and Genomic Instability Induced by Drought Stress in Wheat (Triticum aestivum L.)

The main purpose of the study was to clarify the effect of selenium (Se) on DNA damage and DNA methylation in wheat (Triticum aestivum L.) plants exposed to polyethylene glycol (PEG)-induced drought stress under in vitro tissue culture. Random amplified polymorphic DNA (RAPD) and coupled restriction enzyme digestion-random amplification (CRED-RA) were utilized to explain the DNA damage grade and variations in DNA methylation patterns, respectively. The outcomes indicate that drought stress gives rise to a rise in RAPD profile variations (as DNA damage) and a decrease in genomic template stability (GTS) rate and DNA methylation changes. According to the RAPD data, the greatest GTS value was computed at 56.9% (5% PEG 6000), and the lowest GTS value was 41.2% (15% PEG 6000), demonstrating the adverse effects of PEG 6000. However, DNA damage can be reduced by treatment with sodium selenate (2, 4, and 6 µM of Na2SeO4) together with PEG (5%, 10%, and 15% PEG 6000)-induced water deficits. Moreover, according to CRED-RA analysis, PEG-induced DNA methylation rates were changed after treating different doses of Se. These data demonstrate that Se dose-dependently modulates both DNA damage and methylation alterations induced by drought in wheat.

Isohydric stomatal behaviour alters fruit vascular flows and minimizes fruit size reductions in drought-stressed 'Hass' avocado (Persea americana Mill.).

Plant water status is important for fruit development, because many fleshy fruits contain large amounts of water. However, there is no information on vascular flows of Persea americana 'Hass' avocado. The aims of this research were to explore the impact of drought stress on the water relationships of the 'Hass' avocado plant and its fruit growth. Well-watered and water-stressed 'Hass' avocado plants were compared. Over 4 weeks, water flows through the shoot and fruit pedicel were monitored using external sap flow gauges. Fruit diameter was monitored using linear transducers, and stomatal conductance (gs), photosynthesis (A) and leaf and stem water potentials (Ѱleaf and Ѱstem) were measured to assess the response of the plants to water supply. In well-watered conditions, the average water inflow to the shoot was 72 g day-1. Fruit water inflow was 2.72 g day-1, but there was water loss of 0.37 g day-1 caused by the outflow (loss back into the tree) through the vascular tissues and 1.06 g day-1 from the fruit skin. Overall, fruit volume increased by 1.4 cm3 day-1. In contrast, water flow into fruit of water-stressed plants decreased to 1.88 g day-1, with the outflow increasing to 0.61 g day-1. As a result, increases in fruit volume were reduced to 0.4 cm3 day-1. The values of A, gs and sap flow to shoots were also reduced during drought conditions. Changes in the hourly time-courses of pedicel sap flow, fruit volume and stem water potential during drought suggest that the stomatal response prevented larger increases in outflow from the fruit. Following re-watering, a substantial recovery in growth rate was observed. In summary, a reduction in growth of avocado fruit was observed with induced water deficit, but the isohydric stomatal behaviour of the leaves helped to minimize negative changes in water balance. Also, there was substantial recovery after re-watering, hence the short-term water stress did not decrease avocado fruit size. Negative impacts might appear if the drought treatment were prolonged.

Solute contributions to osmotic adjustment in leaf segments of wheat (Triticum aestivum L.) exposed to polyethylene glycol-induced water deficit

ABSTRACT This study examined osmotic adjustment (OA) and solutes accumulated in leaf segments of wheat cultivar Hartog exposed to polyethylene glycol (PEG)-induced water deficit (WD) in laboratory experiments. Additional 10 mM K+ or Na+ added to basal solution with PEG −0.5 MPa enhanced leaf OA by up to 100%. Omission of nitrogen from the basal solution suppressed the expression of OA in leaf segments, but the addition of 10 mM NO3 – increased leaf OA by up to 81%. K+ and glycinebetaine were not accumulated in leaf segments exposed to WD under PEG −0.5 MPa during 48 h, but Na+, Cl−, proline and total soluble sugars accounted for up to 21, 20, 7 and 40% of OA, respectively. Total soluble sugars were the largest contributor to OA and may also contribute to membrane stability. Further data are needed on accumulation of leaf NO3 − and glycinebetaine in response to increasing nitrogen supply, and on which other inorganic and organic solutes may also contribute to OA under PEG-induced WD. Laboratory experiments with leaf segments exposed to WD under −0.5 MPa PEG, and with 10 mM K+, Na+ or NO3 − added to the basal solution, could provide an effective and rapid pre-screen of diverse germplasm sources for OA expression. Selected genotypes should then be validated by exposure to soil WD for agronomic evaluation, and for OA expression under field WD.

Does Sodium Nitroprusside Alleviate Water Deficit Stress in Impatiens walleriana Shoots Grown In Vitro?

Impatiens walleriana is a decorative horticultural plant species. Commercial production requires that the plants be brought to market, often accompanied by reduced water content during transport. Drought significantly affects metabolic processes in plants. The effects of polyethylene glycol (PEG)-induced water deficit on shoots of I. walleriana were investigated using different mechanisms at the biochemical level. In addition, the potential water deficit-ameliorating effect of sodium nitroprusside (SNP) was tested. Shoots of I. walleriana were initially grown on MS media supplemented with SNP (50, 100 and 250 μM). After pre-treatments, shoots were further transferred to media supplemented with PEG8000 (3%) and/or SNP (50, 100 and 250 μM). Water deficit conditions increased proline, photosynthetic pigments, malondialdehyde (MDA), H2O2, total phenolic content and antioxidant activity. In addition, PEG-induced water deficit increased superoxide dismutase (SOD) and peroxidase (POX) activities but decreased catalase (CAT) activity. SNP did not significantly affect photosynthetic pigments and total phenolic content but increased proline accumulation, MDA and H2O2 content, especially when applied simultaneously with PEG. Moreover, none of the investigated SNP pretreatments significantly altered the activities of SOD, POX, and CAT in I. walleriana. The results indicate that exogenous application of SNP effectively alleviated water deficit stress in shoots of I. walleriana grown in vitro.

Exogenous Salicylic Acid Alleviates Water Deficit Stress by Protecting Photosynthetic System in Maize Seedlings

Water deficit is a significant abiotic stress affecting crop growth and production. While many studies have indicated that salicylic acid (SA) plays a crucial role in mitigating the detrimental effects of environmental stress on plants, its mechanism regulating the photosynthetic adaptability of maize seedlings under water deficit is still unclear. This study aimed to investigate the impact of exogenous SA on maize seedling performance under polyethylene glycol (PEG)-induced water deficit. The results showed that PEG treatment destroyed the integrity of chloroplast and reduced chlorophyll content and photosynthesis rate (Pn), leading to growth retardation of maize seedlings with lower biomass accumulation and leaf relative water content (RWC). Moreover, chlorophyll fluorescence index, including potential photochemical activity (Fv/Fo), maximum Photosystem II (PSII) quantum yield (Fv/Fm), and energy captured by PSII reaction center for electron transfer (Eto/RC), were decreased, but energy dissipated by unit reaction center (DIo/RC) was enhanced in maize seedlings under water deficit. In addition, PEG treatment also significantly declined the activity of Rubisco and Rubisco activase (RCA) in maize seedlings. In contrast, SA treatment enhanced the content of chlorophyll, as well as the transcription level of psbA, and RCA and Rubisco small subunit (rbcS) reduced the damaging effects of PEG treatment by protecting the integrity of chloroplast and repairing the damaged PSII reaction center, thus positively regulating photosynthetic reaction and water-deficit tolerance in maize seedlings. Our data implied that SA played an important regulatory role in plant resistance to water-deficit stress, and the result will further supply the regulatory network of SA-mediated photosynthetic adaptability.

Brassinolide and Zinc Effect on Physio-Biochemistry of Garden Pea (Pisum sativum L.) under Water Deficit Condition

Background- This experiment was carried out to examine the impact of exogenously applied concentrations of epi-brassinolide (e-BL) and zinc (Zn) on the physio-biochemical processes that occur in garden pea (Pisum sativum L.), when the plant is subjected to water-deficit stress. Methods- A polyhouse experiment was performed using a completely randomized design with three replicates by e-BL pre-treating the seeds of garden pea genotype HUP-2 with concentrations of 0.01 and 0.05 mM and/or Zn before subjecting the plants to an induced water deficit stress at various stages of growth and development. Results- Garden pea seeds that had been pre-treated with e-BL, and then supplied with Zn micronutrients showed a favorable reaction against a water shortage in terms of membrane stability and a variety of enzymatic activity. It is possible for e-BL and Zn to mitigate the impact of post-anthesis water shortage, which is more likely to result in yield reduction. Both seed pre-treatment with e-BL and basal administration of Zn have shown to be effective in protecting the HUP-2 genotype of Garden pea from the negative effects of water deficiency.

Exogenous abscisic acid (ABA) and jasmonate (JA) promote metabolic regulation in Jacarandá-Pardo (Machaerium villosum Vog.) seedlings under PEG-induced water deficit

Plant hormones are essential in regulating plant responses to water deficit. However, there is little information on their effects on the growth of Cerrado plants under water deficit. This study aimed to investigate how exogenous abscisic acid (ABA) and jasmonic acid (JA), used separately, can minimize the effects of induced water deficit by polyethylene glycol (PEG-6000) in Machaerium villosum seedlings. The experiment had four treatments: 1) control: half-strength Hoagland's nutrient solution; (2) PEG-water deficit: Hoagland's solution supplemented with PEG (−1.0 MPa); (3) PEG-water deficit + 100 μM ABA; and (4) PEG-water deficit + 100 μM JA. Seedlings of M. villosum were collected separately at 0, 3, 7, and 14 days after treatment. At the end of 14 days, the relative water content (RWC) substantially decreased by 29.69% in the PEG treatment, followed by 14.59 and 13.83% in the PEG+ABA and PEG+JA treatments, respectively. The PSII photochemistry quantum yield (Fv/Fm) differed significantly between control and PEG treatments at seven days. Oxidative stress was detected after three days of water deficit. The superoxide anion (O₂⁻) content gradually increased in the PEG and PEG + ABA treatments, while the PEG + JA treatment interacted positively with the suppression of O₂⁻ production. Hydrogen peroxide (H2O2) production increased by 132.2 and 66.2% at seven days and 277.4 and 131.3% at 14 days in the PEG and PEG + ABA treatments, respectively. Metabolic profiling analysis showed that ABA and JA affected common water deficit-induced metabolic pathways. PEG and PEG + ABA treatments accumulated carbohydrates and some amino acids responsible for osmotic adjustment and energy production. Conversely, the PEG + JA treatment accumulated caffeic acid, vanillic acid, and quinic acid related to secondary metabolism, antioxidant compounds, and fatty acids, important membrane repair agents.

In Vitro Selection of Mungbean Genotypes for Drought Tolerance by Polyethylene Glycol Induced Water Defi cit

Drought stress is a major constraint affecting growth and yield of several economic crops including mungbean [Vigna radiata (L.) Wilczek]. In vitro selection for drought tolerance is an alternative method for early determination of drought tolerant plants. The objective of this study was to perform in vitro selection of mungbean genotypes under water stress induced by polyethylene glycol (PEG) 6000. Seeds of 18 genotypes were germinated in Murashige and Skoog (MS) liquid medium supplemented with different concentrations of PEG 6000 (0, 8, 12 and 16%). Germination percentage, promptness index, root length tolerance index, seed vigor index, seedling length tolerance index, seedling fresh weight tolerance index and seedling dry weight tolerance index were measured. The results showed reduced germination and growth in all genotypes with increasing PEG concentrations. Various genotypes responded differentially at 16% PEG. Interestingly, K-851, EG-MG-13, VI000411 A-G, and CES 44 showed a higher germination percentage, root length, seedling length and seed fresh weight than other genotypes, demonstrating their drought tolerance potential. However, their water stress responses need to be confi rmed under greenhouse and/or fi eld conditions before they can be used as parents in breeding programs to improve drought tolerance.

Impact of mannitol and poly ethylene glycol 6000 induced water deficit on plant biomass and major secondary metabolites in Centella asiatica (L.) Urb. in vitro

Low water potential related stresses are regulated by modifying water uptake and loss to avoid low water potential, accumulating solutes which in turn enhance active principles and its gene expressions. Present study examined effect of in vitro induced absorption of mannitol and PEG (poly ethelene glycol) 6000 in Indian pennywort, Centella asiatica (L.) Urb., neutraceutical plant, evidenced by phenotypic, molecular and phytochemical analyses. Both mannitol and PEG 6000 induce water deficit conditions in plants and retarded normal plant biomass in terms of fresh and dry weights. These effects were significantly less severe in plants subjected to mannitol, compared to PEG. PEG and mannitol imposed water deficit, resulted in decline in major active compound, asiaticoside evidenced by HPTLC of asiaticoside content. Differential expression of some selected key genes in the asiaticoside pathway including squalene synthase and β amyrin synthase by qPCR, confirmed decrease in transcript level expression of asiaticoside, whereas upregulated transcript level expression was observed in cycloartenol synthase for synthesis of phytosterols. Estimation of total flavonoids and phenolics under different water deficit conditions were found declined. In conclusion, water deficit by mannitol and PEG 6000 can significantly affects processes associated with biomass growth and ability to synthesize secondary metabolites in C. asiatica.

Foliar application of potassium nitrate induces tolerance to water deficit in pre-flowering sorghum plants

The objective of this study was to evaluate the the ability of foliar application of potassium nitrate (KNO3) to induce water deficit tolerance in sorghum plants (Sorghum bicolor cv. P898012) subjected to water deficit at pre-flowering. The experiment was conducted under greenhouse conditions with 4 treatments: field capacity (FC), water deficit (WD), field capacity + KNO3 (FC + KNO3), and water deficit + KNO3 (WD + KNO3). Two foliar applications of 3% (m/v) KNO3 were made, the first on day zero of stress and the second on the fifth day. All analyses were performed after 12 days of stress (end of stress). Foliar application of KNO3 to irrigated plants led to increases in relative chlorophyll content, photosynthetic rate, stomatal conductance, transpiration, and carboxylation efficiency. It also induced increases in leaf concentrations of P, Mg, S, Cu, and Fe, in addition to height growth. Under water deficit conditions, plants treated with KNO3 presented higher relative chlorophyll content, leaf area, photosynthetic rate, stomatal conductance, transpiration, carboxylation efficiency, and higher levels of P, K, Mg, S, Cu, and Fe than those not treated with KNO3. The morphometry of the root system was not altered by the treatments. In addition, plants treated with KNO3 under water deficit conditions showed higher growth and a grain yield 32.2% higher than those that did not receive KNO3. These results demonstrated that KNO3 applied to the leaves induced water deficit tolerance in sorghum plants subjected to severe water stress at pre-flowering.

The soybean Phytoglobin1 (GmPgb1) is involved in water deficit responses through changes in ABA metabolism

Soybean (Glycine max), a major grain crop worldwide, is susceptible to severe yield loss due to drought. Soybean plants over-expressing and downregulating the soybean Phytoblobin1 (GmPgb1) were evaluated for their ability to cope with polyethylene glycol (PEG)-induced water deficit. Sense transformation of GmPgb1, which was more expressed in shoot tissue relative to roots, increased overall plant performance and tolerance to water stress by attenuating the PEG depression of photosynthetic gas exchange parameters and chlorophyll content, as well as reducing leaf injury and promoting root growth. The higher plant relative water content, as a result of GmPgb1 over-expression, was associated with higher transcript levels of three aquaporins: GmTIP1;5 and GmTIP2;5 GmPIP2;9, known to confer water stress tolerance. Opposite results were observed in plants suppressing GmPgb1, which were highly susceptible to PEG-induced stress. Transcriptional and metabolic analyses revealed higher ABA synthesis in dehydrating leaves of plants over-expressing GmPgb1 relative to those suppressing the same gene. The latter plants exhibited a transcriptional induction of ABA catabolic enzymes and higher accumulation of the ABA catabolite dehydrophaseic acid (DPA). Administration of 8′-acetylene ABA, an ABA agonist resistant to the ABA catabolic activity, was sufficient to restore tolerance in the GmPgb1 down-regulating plants suggesting that regulation of ABA catabolism is as important as ABA synthesis in conferring PEG-induced water stress tolerance. Screening of natural soybean germplasm also revealed a rapid and transient increase in foliar GmPgb1 in tolerant plants relative to their susceptible counterparts, thus confirming the key role exercised by this gene during water stress.

Effect of exogenous alpha-tocopherol on physio-biochemical attributes and agronomic performance of lentil (Lens culinaris Medik.) under drought stress.

Water being a vital part of cell protoplasm plays a significant role in sustaining life on earth; however, drastic changes in climatic conditions lead to limiting the availability of water and causing other environmental adversities. α-tocopherol being a powerful antioxidant, protects lipid membranes from the drastic effects of oxidative stress by deactivating singlet oxygen, reducing superoxide radicals, and terminating lipid peroxidation by reducing fatty acyl peroxy radicals under drought stress conditions. A pot experiment was conducted and two groups of lentil cultivar (Punjab-2009) were exposed to 20 and 25 days of drought induced stress by restricting the availability of water after 60th day of germination. Both of the groups were sprinkled with α-tocopherol 100, 200 and 300 mg/L. Induced water deficit stress conditions caused a pronounced decline in growth parameters including absolute growth rate (AGR), leaf area index (LAI), leaf area ratio (LAR), root shoot ratio (RSR), relative growth rate (RGR), chlorophyll a, b, total chlorophyll content, carotenoids, and soluble protein content (SPC) which were significantly enhanced by exogenously applied α-tocopherol. Moreover, a significant increase was reported in total proline content (TPC), soluble sugar content (SSC), glycine betaine (GB) content, endogenous tocopherol levels, ascorbate peroxidase (APX), catalase (CAT) peroxidase (POD) and superoxide dismutase (SOD) activities. On the contrary, exogenously applied α-tocopherol significantly reduced the concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2). In conclusion, it was confirmed that exogenous application of α-tocopherol under drought induced stress regimes resulted in membrane protection by inhibiting lipid peroxidation, enhancing the activities of antioxidative enzymes (APX, CAT, POD, and SOD) and accumulation of osmolytes such as glycine betaine, proline and sugar. Consequently, modulating different growth, physiological and biochemical attributes.

Potassium supply modulates Eucalyptus leaf water-status under PEG-induced osmotic stress: integrating leaf gas exchange, carbon and nitrogen isotopic composition and plant growth.

The objective of this study was to quantify the effect of potassium (K) supply on osmotic adjustment and drought avoidance mechanisms of Eucalyptus seedlings growing under short-term water stress. The effects of K supply on plant growth, nutritional status, leaf gas exchange parameters, leaf water potential (Ψw), leaf area (LA), stomatal density (SD), leaf carbon (C) and nitrogen (N) isotopic compositions (δ13C and δ15N ‰) and leaf C/N ratio under polyethylene glycol (PEG)-induced water deficit were measured. Under both control (non-PEG) and osmotic stress (+PEG) conditions, K supply increased plant growth, boosting dry matter yield with decreased C/N leaf ratio and δ15N ‰ values. The +PEG significantly reduced LA, plant growth, dry matter yield, Ψw, number of stomata per plant and leaf gas exchange, relative to non-PEG condition. Potassium supply alleviated osmotic-induced alterations in Eucalyptus seedlings by better regulating leaf development as well as SD, thus improving the rate of leaf gas exchange parameters, mesophyll conductance to CO2 (lower δ13C ‰ values) and water use efficiency (WUE). Consequently, K-supplied plants under drought better acclimated to osmotic stress than K-deficient plants, which in turn induced lower CO2 assimilation and dry matter yield, as well as higher leaf δ13C ‰ and δ15N ‰ values. In conclusion, management practices should seek to optimize K-nutrition to improve WUE, photosynthesis-related parameters and plant growth under water deficit conditions.

Key photoprotective pathways of a shade-tolerant plant (Alpinia oxyphylla) for precipitation patterns change during the dry season: thermal energy dissipation and water-water cycle

Alpinia oxyphylla Miq is a shade-tolerant plant that grows under rubber trees. The decreased precipitation often leads to limitation of photosynthesis and productivity of A. oxyphylla during the dry season. However, the effects of the precipitation patterns on the photosynthesis and the photoprotective strategies of A. oxyphylla remains unclear. Herein, we examined how CO2 assimilation, light energy partitioning and reactive oxygen species (ROS) metabolism are affected by simulated precipitation patterns change. The change of precipitation patterns induced water deficits of different intensities and durations. With the decreased precipitation, stomatal conductance (Gs) and net CO2 assimilation rate (Pn) significantly decreased, resulting in excess excitation energy and over-accumulation of ROS, and further caused lipid peroxidation of photosynthetic apparatus. The phenomenon was exacerbated by extending the interval between precipitation. In addition, the decreased precipitation induced the xanthophyll cycle effectively dissipating excess excitation energy. Through the water-water cycle, a greater proportion of electron flux was shuffled to molecular oxygen (O2) to produce superoxide anion (O2•−), especially in plants under natural precipitation (W; 25 mm/month). This may be because the energy partitioning mechanism of A. oxyphylla can efficiently dissipate excessive excitation energy and reduce PSⅡ photoinhibition, thus rapidly adapting to precipitation patterns change. On the other hand, the decreased precipitation improved the capacity of ROS detoxification in the water-water cycle and reduced lipid peroxidation in W plants, which were reflected by the increase of SOD and CAT activities, and a partial enhancement of antioxidant enzymes and antioxidant metabolism in the water-water cycle. However, the down-regulation of antioxidant systems in W- plants (decreased precipitation; 10 mm/month) further accelerated ROS accumulation and the ability of ROS-scavenging might be partially compensated by ROS accumulation, which may had been a primary cause for limited the antioxidant protection. Overall, when CO2 assimilation reduced with the decreased precipitation, A. oxyphylla can form a photoprotective mechanism, both thermal energy dissipation and water-water cycle are crucial photoprotective pathways against photodamage in photosynthetic apparatus.

Effects of induced water deficit and biofertilization on growth dynamics and bulb yield of onion (Allium cepaL.) in a neotropical semi-arid environment

In a scenario of world population increase and climate change, an efficient use of water is key for agricultural production. Onion is one of the most profitable crops and can adapt to particular conditions of water stress. The objective of this research was to determine growing degree-days and accumulated radiation under non-stress conditions and yield of an F1 2000 hybrid of onion (Allium cepa L.) under water deficit (WD) and biofertilization in a semi-arid environment. An established nutrient requirement of 247 kg N, 240 kg P2O5(105 kg P), 240 kg K2O (199 kg K), and two irrigation factors were applied: normal irrigation with a daily and WD with a 3 d interval irrigation frequencies. The effect of biofertilization was evaluated through the inoculation of a microbial consortium (MC) in combination with four NPK fertilizer treatments. The crop accumulated 1334 degree-days and 1188 MJ m−2·d−1at the time of harvest at 71 d after transplanting. The yield was 36 t·ha−1, similar under both irrigation conditions; and the WD treatment resulted in a 35% water savings, a 47% and 65% increase in water use efficiency and modulus of elasticity, respectively. The MC resulted in a 50% NPK savings under non-limiting water conditions and produced a similar yield compared with the 100% NPK non-inoculated control. The lower irrigation frequency together with the 100% NPK fertilization dose without the MC and the use of the microorganisms and the 50% NPK treatment without water stress are recommended as agrosustainable practices for onion production.

Identification of rice genotypes for seedling stage multiple abiotic stress tolerance

Under changing climatic conditions, crops are expected to experience combination of abiotic stresses rather than challenged by a single abiotic stress and hence, breeding for specific abiotic stress tolerance is unavailing. Exposure of crops to abiotic stress during seedling stage leads to poor crop establishment due to early death of seedlings. Hence, tolerance to multiple abiotic stress at seedling stage is imperative for breeding crops. Therefore, there is a need to identify donors for multiple abiotic stress tolerance in rice. Our study aimed at identifying rice genotypes which has multiple abiotic stress tolerance particularly for salinity, drought and heat stress, the most common abiotic stresses under tropical condition. We hypothesis that since abiotic stress tolerance mechanism involves multi-layered regulatory networks, identifying genotypes conferring tolerance through overlapping mechanisms across different abiotic stress might be a multiple abiotic stress tolerant genotype. An important adaptive mechanism for stress tolerance is high root to shoot ratio and this physiological trait has been used as a criterion for tolerance. Twelve rice genotypes were grown under induced water deficit, salinity and high temperature conditions and seedling growth parameters were recorded. Root shoot ratio on length basis was derived from the recorded parameters and the data was normalized by Z distribution and plotted using scatter plot across stresses. KR15058 and KR15007 were identified as the seedling stage multiple abiotic stress tolerant lines by scatter plot analysis. These lines are promising source for the crop improvement programme for developing a multiple stress tolerant genotype with superior agronomical background.

Combined Effects of Induced Water Deficit and Foliar Application of Silicon on the Gas Exchange of Tomatoes for Processing

The beneficial effects of silicon (Si) on plants have been widely reported for its fruit qualitative improvements, growth gains, and protection against abiotic and biotic stresses. This study aimed to evaluate the combined effect of soil water potential (Ψs) (−30 and −60 kPa) and the foliar application of Si (0.0 (control), 1.0, 2.0, 3.0, and 4.0 g L−1) in the development of tomatoes grown in a greenhouse. We evaluated the biometric parameters and gas exchange in three periods (20, 34, and 48 days after planting). The rates of transpiration (E), stomatal conductance (gs), and net photosynthesis assimilation (An) were lower when the plants were subjected to water deficit. The foliar application of Si attenuated the effect of the water deficit in both levels applied to the crop. A high response was observed at −60 kPa, regardless of the evaluated period. However, a significant effect was not observed on the relative chlorophyll index and biomass accumulation when Si was applied. A foliar application up to 2.8 g L−1 promotes increases in An,gs, and E. It is highlighted that Si can promote improvements in gas exchange when plants are affected by a water deficit.

Leaf chlorophyll content in North Sulawesi (Indonesia) local rice cultivars subjected to polyethylene glycol (PEG) 8000-induced water deficit at the vegetative phase

Abstract. Nio SA, Pirade M, Ludong DPM. 2019. Leaf chlorophyll content in North Sulawesi (Indonesia) local rice cultivars subjected to polyethylene glycol (PEG) 8000-induced water deficit at the vegetative phase. Biodiversitas 20: 2462-2467. Climate change can result in drought stress in the environment and this condition reduces rice production. Polyethylene glycol (PEG) is used to induce water deficit, because it is able to decrease water potential in the solution. The present study aimed to evaluate the physiological response of North Sulawesi local rice (cvs. Superwin, Ombong, Burungan, and Temo) to PEG 8000-induced water deficit based on the leaf chlorophylls (a, b and total chl.) content at the vegetative phase. The results of this study showed that PEG 8000-induced water deficit with media water potential (WP) -0.25 and -0.5 MPa decreased the content of leaf total chlorophyll and leaf chlorophyll a. The longer treatment period could reduce the contents of leaf total chlorophyll, chlorophyll a and chlorophyll b. The content of leaf chlorophyll total and chlorophyll a were potential physiological indicators for North Sulawesi local rice response to PEG 8000-induced water deficit.