Plants face a combination of different abiotic stresses under field conditions which are lethal to plant growth and production. Simultaneous occurrence of chilling and drought stresses in plants due to the drastic and rapid global climate changes, can alter the morphological, physiological and molecular responses. Both these stresses adversely affect the plant growth and yields due to physical damages, physiological and biochemical disruptions, and molecular changes. In general, the co-occurrence of chilling and drought combination is even worse for crop production rather than an individual stress condition. Plants attain various common and different physiological and molecular protective approaches for tolerance under chilling and drought stresses. Nevertheless, plant responses to a combination of chilling and drought stresses are unique from those to individual stress. In the present review, we summarized the recent evidence on plant responses to chilling and drought stresses on shared as well as unique basis and tried to find a common thread potentially underlying these responses. We addressed the possible cross talk between plant responses to these stresses and discussed the potential management strategies for regulating the mechanisms of plant tolerance to drought and/or chilling stresses. To date, various novel approaches have been tested in minimizing the negative effects of combine stresses. Despite of the main improvements there is still a big room for improvement in combination of drought and chilling tolerance. Thus, future researches particularly using biotechnological and molecular approaches should be carried out to develop genetically engineered plants with enhanced tolerance against these stress factors.

/pdf/chilling-and-drought-stresses-in-crop-plants-implications-3zvxfs5ueg.pdf

Chilling and Drought Stresses in Crop Plants: Implications, Cross Talk, and Potential Management Opportunities

Plants are exposed to any number of potentially adverse environmental conditions such as water deficit, high salinity, extreme temperature, submergence, etc. These abiotic stresses adversely affect the plant growth and productivity. Nowadays various strategies are employed to generate plants that can withstand these stresses. In recent years, seed priming has been developed as an indispensable method to produce tolerant plants against various stresses. Seed priming is the induction of a particular physiological state in plants by the treatment of natural and synthetic compounds to the seeds before germination. In plant defense, priming is defined as a physiological process by which a plant prepares to respond to imminent abiotic stress more quickly or aggressively. Moreover, plants raised from primed seeds showed sturdy and quick cellular defense response against abiotic stresses. Priming for enhanced resistance to abiotic stress obviously is operating via various pathways involved in different metabolic processes. The seedlings emerging from primed seeds showed early and uniform germination. Moreover, the overall growth of plants is enhanced due to the seed-priming treatments. The main objective of this review is to provide an overview of various crops in which seed priming is practiced and about various seed-priming methods and its effects.

Seed priming for abiotic stress tolerance: an overview

Plants are challenged by a variety of biotic or abiotic stresses, which can affect their growth and development, productivity, and geographic distribution. In order to survive adverse environmental conditions, plants have evolved various adaptive strategies, among which is the accumulation of metabolites that play protective roles. A well-established example of the metabolites that are involved in stress responses, or stress tolerance, is the low-molecular-weight aliphatic polyamines, including putrescine, spermidine, and spermine. The critical role of polyamines in stress tolerance is suggested by several lines of evidence: firstly, the transcript levels of polyamine biosynthetic genes, as well as the activities of the corresponding enzymes, are induced by stresses; secondly, elevation of endogenous polyamine levels by exogenous supply of polyamines, or overexpression of polyamine biosynthetic genes, results in enhanced stress tolerance; and thirdly, a reduction of endogenous polyamines is accompanied by compromised stress tolerance. A number of studies have demonstrated that polyamines function in stress tolerance largely by modulating the homeostasis of reactive oxygen species (ROS) due to their direct, or indirect, roles in regulating antioxidant systems or suppressing ROS production. The transcriptional regulation of polyamine synthesis by transcription factors is also reviewed here. Meanwhile, future perspectives on polyamine research are also suggested.

/pdf/polyamines-function-in-stress-tolerance-from-synthesis-to-4t4fp96nkz.pdf

Polyamines function in stress tolerance: from synthesis to regulation

THE best adjective to describe this work is \"sweep11 ing.\" The range of subject matter is so broad that it can almost be described as containing everything except fuzzy set theory. Included are explicit discussions of the basics of probability (relegated to an appendix); the practice of problem solving; testing hypotheses about statistical parameters; calculating and interpreting confidence limits; tolerance limits and prediction limits; setting up and interpreting control charts; design of experiments; analysis of variance; line and surface fitting; and maximum likelihood procedures. If you can think of something that is not in this list, then it probably means I have overlooked it.

Experiments: Planning, Analysis, and Parameter Design Optimization

Rice belongs to tropical and subtropical environments and is extremely sensitive to chilling stress particularly during emergence and early stages of seedling development. Seed priming can be a good approach to enhance rice germination and stand establishment under chilling stress. The present study examined the role of different seed priming techniques viz., hydropriming, osmopriming, redox priming, chemical priming, and hormonal priming, in enhancing the chilling tolerance in rice. The most effective reagents and their pre-optimized concentrations based on preliminary experiments were used in this study. Two different rice cultivars were sown under chilling stress (18˚C) and normal temperatures (28˚C) in separate growth chambers. A non-primed control treatment was also maintained for comparison. Chilling stress caused erratic and delayed germination, poor seedling growth, reduced starch metabolism and lower respiration rate, while higher lipid peroxidation and hydrogen peroxide accumulation in rice seedlings of both cultivars. Nevertheless, all the seed priming treatments effectively alleviated the negative effects of chilling stress. In addition, seed priming treatments triggered the activities of superoxide dismutase, peroxidase, and catalase, and enhanced the accumulations of glutathione and free proline in rice seedlings, which suggests that these measures help prevent the rice seedlings from chilling induced oxidative stress. Chemical priming with selenium and hormonal priming with salicylic acid remained more effective treatments for both rice cultivars under chilling stress than all other priming treatments. The better performance and greater tolerance of primed rice seedlings was associated with enhanced starch metabolism, high respiration rate, lower lipid peroxidation, and strong antioxidative defense system under chilling stress.

/pdf/physiological-and-biochemical-mechanisms-of-seed-priming-3ypl0xyea4.pdf

Physiological and Biochemical Mechanisms of Seed Priming-Induced Chilling Tolerance in Rice Cultivars

Counterfeit seeds cause a large loss in seed industry and crop production. Present study was undertaken to find a new anti-counterfeiting technology by labeling seeds with a fluorescent compound, safranine T (ST). Response surface analysis (RSA) experiment with two factors (ST concentration and seed soaking time) of 14 combinations was performed to investigate the ST effects on seed vigor and fluorescence showing in seedlings of two tobacco varieties, MS Yunyan 85 and Honghua Dajinyuan. After soaking in ST solutions, tobacco seeds were germinated for 16 days, then the germination index (GI), vigor index (VI), length of roots and shoots were determined. The optimum combinations of ST concentration and soaking time on GI, VI and length of shoots and roots were 0.57–0.69 mg/ml and 6.77–9.34 h for MS Yunyan 85 and 0.51–0.80 mg/ml and 5.81–7.39 h for Honghua Dajinyuan, respectively. Meanwhile, tobacco seedlings, treated with ST solutions from 0.3 to 1.5 mg/ml showed obviously fluorescence under illumination of green light. It suggests that soaking tobacco seeds in safranine T solution of suitable concentration can be used as a labeling technique for anti-counterfeiting in tobacco seeds.

A new anti-counterfeiting method: fluorescent labeling by safranine T in tobacco seed

The soybean is an important food crop worldwide. Drought during the first pod stage significantly affects soybean yield, and understanding the metabolomic and physiological changes in soybeans under drought stress is crucial. This study identified the differential metabolites in initial pod stage soybean leaves under polyethylene glycol-simulated drought stress, using ultra performance liquid chromatography and tandem mass spectrometry, and the physiological indexes related to drought resistance.Physiologically, drought resistance also generates enzyme and antioxidant activity; levels of superoxide dismutase, peroxidase, and catalase first increased and subsequently decreased, while those of soluble sugar, soluble protein, malondialdehyde, and proline content increased in both varieties. The contents of CAT, proline and soluble sugar in Heinong 44 (HN44) were higher than those in Heinong 65 (HN65), and the contents of MDA were lower than those in HN65. In metabolomics, the OPLS-DA model was used to screen different metabolites. KEGG analysis showed that the two varieties resisted drought through different ways. Amino acid metabolism and lipid metabolism play a key role in drought resistance of the two varieties, respectively. TCA cycle was one of the core pathways of drought resistance in two varieties. Changes in the content of L-Asparagine and citric acid may be one of the reasons for the difference in drought resistance between the two varieties.We think that the reasons of drought resistance among soybean varieties are as follows: the main metabolic pathways are different under drought stress; the contents of metabolites in these metabolic pathways are different; some physiological indexes are different, such as MDA, CAT, proline content and so on. Our study enhances the understanding of the metabolomic soybean drought stress response and provides a reference for soybean drought resistance breeding. 

/pdf/physiology-and-metabonomics-reveal-differences-in-drought-2tugi51z.pdf

Physiology and metabonomics reveal differences in drought resistance among soybean varieties

The invention discloses a method for identifying the seedling stage stress resistance of a tobacco variety. The method comprises the following steps of: disinfecting seeds of the tobacco variety to be tested, germinating the disinfected seeds under adverse condition and normal condition for 16 days and calculating a germination percentage and a germination index; germinating the seeds under normal condition for 7 days, allowing the buds to grow under the adverse condition for 5 days, allowing the buds to grow under normal condition for 4 days, allowing the buds to grow under normal condition for 16 days and testing the heights and dry weights of seedlings; and taking relative values of the germination percentage, the germination index, the seedling heights and the dry weights of the seedlings as indexes for evaluating the seedling stage stress resistance of the tobacco variety, setting a property relative value to be xL/xN, performing cluster analysis on the property relative value by a group average method and determining the seedling stage stress resistance of the tobacco variety to be tested according to the average value of property relative values. The method has the advantages of simple and convenient operation, low cost, rapid identification, easy operation, stable and accordant result, capability of eliminating the difference between the genetic backgrounds of different varieties due to the adoption of the property relative value as the index for evaluating the seedling stage stress resistance of the variety and good application prospect.

Method for identifying seedling stage stress resistance of tobacco variety

The invention discloses a method for shortening the sprouting time of a tobacco pill seed and improving the cold resistance ability thereof. 50-100mg/L of gibberellin solution is used for the priming treatment for 24-36 hours on a tobacco seed which is sterilized and cleaned. After cleaning and drying, the seed is made into the tobacco pill seed according to a conventional process. The method has the advantages of simple operation and low cost. The activity and the seedling quality of the obtained pill seed are obviously improved. The sprouting is fast with unanimous shoot. Under the stress of low temperature, the tobacco pill seed still maintains higher sprouting trend, higher sprouting rate and higher sprouting index. With high activity, the pill seed is provided with obviously strengthened resistance to low temperature and has perfect market application prospect.

Method for reducing germinating time of tobacco coating pilled seeds

Pollen vigor is a prerequisite for fertilization and seed development. In the present research, the pollen of two tobacco varieties of Yunyan87 and K236 were collected in four different flowering stages. Pollen germination rate and the length of pollen tube were tested. Nine physiological and biochemical parameters of putrescine (Put), spermidine (Spd), spermine (Spm), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), malondialdehyde (MDA) and relative electrolyte leakage (REL) were examined. Multiple linear regression was adopted to determine the relationship between all parameters and pollen vigor. The results suggested that Spd could be used as a valuable parameter to predict pollen vigor for Yunyan87 and MDA could be used as a valuable parameter to predict pollen vigor for K236 in different flowering stages. The results also suggested that tobacco pollen collected in petals unfurling stage and full blooming stage had the highest vigor and unfurling stage was the best stage for pollen collection.

	 

	Key words: Pollen vigor, polyamine, antioxidant enzyme, pollen germination.

https://wwmw.academicjournals.org/article/article1380905493_Ma et al.pdf

Relation between changes in polyamine, protective enzyme activity and pollen vigor of tobacco in different flowering stages

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