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PHYSIOLOGICAL PARAMETERS GOVERNING DROUGHT TOLERANCE IN MAIZE

PHYSIOLOGICAL PARAMETERS GOVERNING DROUGHT TOLERANCE IN MAIZE

In majority of the genotypes, transpiration rate decreased under severe stress (IR3) as compared to control (WW) and leaf temperature increased by 2-4ºC. Genotypes having moderate transpiration rates and less increase in leaf temperature were considered desirable to some extent (Table 2). Kirkham et al. (1984), Ristic and Cass (1991) supported the similar views. Genotypes viz., 209, 295, 536 x 295 and 1352 x 1344 had more transpiration rate under severe stress but showed less increase in leaf temperature (0.5 – 1ºC). This may be probably due to cooling of the leaf surfaces because of excessive loss of water though transpiration that resulted less leaf temperature which help the plant to tolerate the excessive heat of the sun (Bolanoes et. al. 1993). Some times when the drought prevails for longer period, then excessive loss of water may result in the desiccation injury and damage the crop.
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PHYSIOLOGICAL AND BIOCHEMICAL EVALUATION OF GROUNDNUT CULTIVARS DIFFERING IN DROUGHT TOLERANCE

PHYSIOLOGICAL AND BIOCHEMICAL EVALUATION OF GROUNDNUT CULTIVARS DIFFERING IN DROUGHT TOLERANCE

applied in the form of urea, SSP and MOP respectively. The remaining 10kg N combined with gypsum (500 kg)/ha was top dressed at 50 per cent flowering stage. Five plants from each plot were collected randomly for estimating the physiological and biochemical parameters, viz. relative water content (Smart 1974), peroxidase activity (Sadasivam and Manickam 1996) and ash content (Mas Ie et aZ. 1992). Chlorophyll stability index (CSI) was estimated by the method described elsewhere (Sairam1994).

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Genotypic variation for agronomical and physiological traits affecting drought resistance in Common Bean (Phaseolus vulgaris L.)

Genotypic variation for agronomical and physiological traits affecting drought resistance in Common Bean (Phaseolus vulgaris L.)

reducing leaf electrolyte ions, are important parameters could be related to drought tolerance mechanisms. This tolerance has been attributed to several drought avoidance and tolerance mechanisms. Among the important visual and morphological traits that may contribute to drought adaptation is the water use efficiency (WUE), relative water content (RWC) which were identified as important traits in response to drought in some cultivars (Anyia and Herzog 2004; Souza et al. 2004). Lu et al. (1998) have shown remarkable positive correlations between yield increases and increases in stomatal conductance (SC) under stress in Pima cotton (Gossypiumbarbadense) and bread wheat (Triticumaestivum) (Waseem et al, 2006). Water deficit significantly increased the proline content of five cowpea genotypes (Hamidou et al. 2007). RWC was a good parameter to discriminate genotypes of traditional crops under water stress (Slabbert et al. 2004).
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The relationship of antioxidant enzymes and some physiological parameters in maize during chilling

The relationship of antioxidant enzymes and some physiological parameters in maize during chilling

The leakage of ions from the root apical segments of the maize seedlings was nearly the same in both cultivars prior to the chilling. After two days of chilling the leakage increased 2-fold in Ultra and only slightly in X0954D (Table 1) indicating changes in the membrane semipermeability. Electrolyte leakage measurements are generally regarded as a useful tool for plants’ cold tolerance estimation (Pinhero et al. 1999). Accordingly, the significant difference between cultivars in conductivity of root surrounding medium shows that cv. Ultra is more sensitive to chilling than cv. X0954D.
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Drought tolerance in transgenic tropical maize (Zea mays L.) by heterologous expression of peroxiredoxin2 gene-XvPrx2

Drought tolerance in transgenic tropical maize (Zea mays L.) by heterologous expression of peroxiredoxin2 gene-XvPrx2

photosynthesis as noted by Flexas et al. (2004). Inflicting dehydration stress during vegetative growth stage, decreased substantially the content of TChl, Chla and b in both the transgenic and conventional plants. This reduction in photosynthetic pigments might have resulted due to reduced RWC. These findings are similar to report by Terzi and Kadioglu (2006) who noted reduction in photosynthetic pigments while studying drought stress tolerance and the antioxidant enzyme system in Ctenanthesetosa. However, the reduction of TChl, Chla and Chlb was less in transgenics than in conventional maize. Transgenic maize maintained a relatively higher content of chlorophylls than the conventional plants. These results complement the reports by Pastori and Trippi (1992) and Zaeifyzadeh and Goliov (2009) who revealed that resistant genotypes of wheat and corn had higher chlorophyll content than sensitive genotypes under the oxidative stress. Lamkemeyer et al. (2006) reported that the absence or presence of Prx Q gene (member of peroxiredoxin gene family) in transgenic A. thaliana affected chlorophyll a fluorescence parameters suggesting a role in maintaining photosynthesis.
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75. Screening of maize (Zea mays L.) hybrids based on drought tolerance under hydroponic conditions

75. Screening of maize (Zea mays L.) hybrids based on drought tolerance under hydroponic conditions

conditions. Drought was estimated by applying PEG-8000. Plants were harvested four weeks after transplanting and the evaluation was done on the basis of various morphological (root length, shoot length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, root shoot ratio, number of leaves) and biochemical parameters (potassium and chlorophyll contents in leaves). Relative leaf water contents and membrane stability index were also measured. The data collected was analyzed statistically at 1% probability level and Least Significant Difference Test (LSD) was applied to separate the significant treatment means. The results showed that the water stress adversely affected on the morphological parameters. The maize hybrid FH-988 had significantly higher (p<0.01) morphological and biochemical parameters and found more drought tolerant. While maize hybrid FH-1137 had lower these parameters as compared to all other maize hybrids and was considered as drought sensitive genotype. Study findings showed that the screening of drought tolerant genotypes could be a better source to mitigate the drought stress impacts on maize in drought prone regions.
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Strengthening the Practical Application of Experiments Assessing Maize Drought Tolerance

Strengthening the Practical Application of Experiments Assessing Maize Drought Tolerance

PubMed literature search yielded 44 articles closely related to maize drought research. They could be classified into three major categories. The first group of studies focused on comparing physiological and biochemical indices of drought resistance across multiple varieties to identify those with high tolerance to water deficit. The second set of studies focused on screening for molecular markers (e.g., chromosomal fragments or genetic loci) associated drought resistance. The third category classified maize varieties according to phenotypic characteristics associated with high drought resistance and tested the reliability of these indicators under normal and drought conditions. Most of the experiments aimed to identify drought resistance of maize were conducted indoors, while others were conducted integrating with field trials (Table 1). In addition, we found several articles that did not confirm with existing best practices and guidelines for such research (Salekdeh et al., 2009), suggesting the need to emphasize optimization before beginning an experiment. Notably, however, QTL research and genome-wide association studies mainly focused on field cultivation of materials. These field-based outcomes tend to be more reliable for practical application than laboratory drought tests. Nonetheless, the fact that most studies are laboratory-oriented is likely because building a controlled, outdoor experimental site that meets the criteria for investigating complex traits is extremely expensive. Therefore, researchers attempt to lower costs while still obtaining usable data through smaller-scale, indoor appraisals of drought resistance.
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Assessment of drought tolerance of 49 switchgrass (Panicum virgatum) genotypes using physiological and morphological parameters

Assessment of drought tolerance of 49 switchgrass (Panicum virgatum) genotypes using physiological and morphological parameters

was observed. The genotypes Blackwell-3, Forestburg, 70SG0021, Sunburst, and BN-11357-63 tended to have higher DSIs (>187.7 %) for WUE. Alternatively, the geno- types 70SG0017, Grif Nebraska 28, 70SG003, BN-12323- 69, and Pathfinder tended to have relatively lower DSIs (<96.5  %) for WUE. Several lowland genotypes, includ- ing BN-13645-64, Alamo, and TEM-SLC, had interme- diate WUEs and DSIs ranging from 122.7 to 154.5  %. The EL reflects cell membrane damage that occurs dur- ing drought stress. In addition, the EL may also affect Tr and Pn (and subsequently affect WUE). Drought stress resulted in an increased EL for all genotypes (Additional Fig. 2 Heatmap and hierarchical clustering for morphological and physiological parameters under well-watered and drought stress conditions in 49 switchgrass genotypes after 30 days of treatment. Clustering analysis of switchgrass genotypes (left) showed two main groups where the group a represents 49 genotypes under the well-watered condition; while group b represents those genotypes under the drought treatment. The cluster- ing analysis of different parameters (top) showed three major groups: group I includes all morphological parameters, group II include the other five physiological parameters, while group III include two key physiological parameters associate with drought tolerance. RWC relative water content, EL electrolyte leakage, Pn photosynthetic rate, g s stomatal conductance, Tr transpiration rate, Ci intercellular CO 2 concentration, WUE water use
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Genetic Variability Studies Involving Drought Tolerance Related Traits in Maize Genotypes

Genetic Variability Studies Involving Drought Tolerance Related Traits in Maize Genotypes

 Under rainfed conditions the analysis of variance for yield and yield contributing parameters showed significant difference for all the characters. Hence, the data on all the seventeen traits which showed significant differences among the entries were subjected to further statistical analysis. In the field evaluation the genotypes were grown under natural rainfed conditions to differentiate lines on the basis of maturity, morphological, yield as well as resource remobilization. The genotypes GM-6 (130.0 days), KG-2 (124.0 days) and KG-1 (122.0 days) mature earlier indicating some kind of escape mechanism in these genotypes under water stress. The ASI was lowest in KDM-72 (2.00 days), KG-2 (2.00 days) and GM-6 (2.53 days) and was highest in C-8 (5.0 days) followed by PM Chari-6(4.33 days) and AM-1 (4.0 days). Among the yield parameters plant height was significantly higher in C-15 (269.0) followed by C-8 (264.4) and C-6 (251.6) similarly, shoot weight was significantly higher in C- 15 (917.5) followed by PM Chari-6 (795.0) and PM-5 (770.0), cob height was significantly higher in C-8 (141.6) followed by C-15 (138.6) and C-6 (125.0), cob length was significantly higher in C-15 (22.33) followed by C-4 (22.06) and KDM- 72 (21.83), no of cobs plant -1 was significantly higher in PM-5 (1.94) followed by C-6 (1.92) and KG-1 (1.92), kernel rows cob -1 was significantly higher in C-4 (16.0) followed by C-15 (14.66) and C-6 (14.66) PM-3 (14.66), PM-4 (14.66), KDM-72 (14.66) and KG-1 (14.66), kernel rows -1 was significantly higher in C-6 (40.66) followed by KDM-72 (39.00) and C-15 (36.66), grains cob -1 was significantly higher in C-6 (596.462) followed by C-4 (570.66) and KDM-72 (570.66), 100-seed weight was significantly higher in C-15 (34.40) followed by PM-5 (34.18) and grain yield plant -1 was significantly higher in C-6 (116.75) followed by C-4 (111.76) and KDM-72 (110.74).
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Physiological responses of chickpea genotypes for drought tolerance under induced moisture stress

Physiological responses of chickpea genotypes for drought tolerance under induced moisture stress

Present studies show genotypic variations in germination, promptness index, seedling length, dry matter and seedling vigour grown under 0, -0.4 and -0.6 Mpa. However, not all these parameters were not proved to be equally effective for screening the genotypes for their tolerance to stress. It was claimed by Fernandez (1992) that selection based on STI (stress tolerance index) would help to evaluate the higher stress tolerance genotypes with good yield potential. Bouslama and Schapaugh (1984) reported same findings in soybean. However, there are other reports (Richards, 1978) indicating germination as a useful criterion in screening for water stress tolerance. Several factors disproved seed quality such as the age of the seed, abiotic factors during plant life, growth and development, harvest and post harvest conditions etc. The response of genotypes may be different to different factors, which could be reflected in their respective seed performances.
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Assessment of drought tolerance of some Triticum L  species through physiological indices

Assessment of drought tolerance of some Triticum L species through physiological indices

Abstract: Wheat is one of the most important crops in the world. Its yield is greatly influenced by global climate change and scarcity of water in the arid and semi-arid areas of the world. So, exploration of gene resources is of importance to wheat breeding in order to improve the crop ability of coping with abiotic stress environment. Wild relatives of wheat are rich repositories of beneficial genes that confer tolerance or resistance not only to drought but also to other environmental stresses. In the present study, the changes in leaf relative water content (RWC), free proline content, and malondialdehyde (MDA) accumulation of five wild wheat species including T. boeticum (YS-1L), T. dicoccum var. dicoccoides (YS-2L), T. araraticum (ALLT), and two cultivated varieties of T. turgidum ssp. durum (MXLK and 87341), with two well-known common wheat cultivars (SH6 and ZY1) possessing strong drought resistance and sensitiveness, respectively, as references were investigated during 3-day water stress and 2-day recovery, in order to assess the drought tolerance of these wild wheat species. The laboratory experiment was conducted under two water regimes (stress and non-stress treatments). Stress was induced to hydroponically grown two weeks old wheat seedlings with 20% PEG 6000. Stress treatment caused a much smaller decrease in the leaf RWC and rise in MDA content in YS-1L compared to the other wheat species. From the data it was obvious that YS-1L was the most drought tolerant among studied species having signifi- cantly higher proline and RWC while lower MDA content under water stress conditions. The order of water stress tolerance of these species according to the three parameters is: YS-1L > YS-2L > SH6 > 87341 > ZY1 > MXLK > ALLT. We speculate that the observed drought stress tolerance at a cellular level was associated with the ability to accumulate proline and high water level conservation.
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Breeding for Drought Tolerance in Maize (Zea mays L )

Breeding for Drought Tolerance in Maize (Zea mays L )

Drought is a multidimensional stress, affecting plants at various levels of their organi- zation over space and time, so that the physiological responses to it are complex and often unpredictable. However, in maize, a major effect of water stress is a delay in silk- ing, resulting in an increase in the anthesis-silking interval (ASI), which is an important cause of yield failures [10]. In fact, typical visual symptoms of drought stress in maize are a change in color from green to green-gray, and rolling of the lower leaves followed by those in the upper canopy. At the same time stomas are closing, photosynthesis is being sharply reduced and growth is slowing. When stress coincides with the 7 - 10 days period prior to flowering, ear growth will slow more than tassel growth and there is a delay in silk emergence relative to pollen shed, giving rise to an interval between anther extrusion and silk exposure [11]. This ASI was shown to be highly correlated with grain yield, in particular kernel number and ear number per plant [10]. At the same time leaf senescence begins at the base of the plant and spreads upwards to the ear. Severe stress at flowering may lead to the complete abortion of ears and the plant becomes barren. Drought-affected ears typically have fewer kernels that will be poorly filled if drought extends throughout grain filling [12].
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Investigating Physiological and Morphological Mechanisms of Drought Tolerance in Wheat (Triticum aestivum L ) Lines with 1RS Translocation

Investigating Physiological and Morphological Mechanisms of Drought Tolerance in Wheat (Triticum aestivum L ) Lines with 1RS Translocation

One of the major physiological responses of plants when exposed to water deficit environment is the elevation of ABA content. In our study, the lines showed inconsistent levels of ABA in water stress treatment. In 2011, the 1RS.1BL had the highest level of ABA whereas in 2012, the highest level was observed for 1RS.1DL (Table 4). Westgate et al. [28] reported up to 30 folds increase in wheat leaf ABA content when grown in drought con- dition. In our study, even though there was significant influence of water regime on ABA content, the variation was not as much. The differences between average ABA content among the tested lines, especially in water stress treatments (both years) are numerically very wide yet not statistically different when considered within each water regime, which could be due lower number of replications and missed values which greatly reduced the power to predict the statistical significance. In the first year, two leaf samples from each line were evaluated where two lines had only one measurement determined due to missing analytical error. In our study, leaf ABA concentration was significantly influenced by the Studies on maize showed that root and leaf ABA concentration during drought plays a vital role in drought adaptive response of the crop and argued that chromosome loci con- trolling the ABA content is also responsible for other drought related traits such as stomatal conductance, root architecture, leaf temperature, etc. [13] [14] [29]. In our study, 1RS.1BL consistently produced higher ABA concentration than other lines which could have played role in its elevated grain yield under water stressed con- ditions.
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Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme with Drought Tolerance

Physiological Effects of Chitosan Coating on Wheat Growth and Activities of Protective Enzyme with Drought Tolerance

Plant produces the super oxide of free radicals and re- active oxygen species in metabolic processes, and under normal physiological conditions of plant, there is a ba- lance between production and elimination of active oxy- gen free radical. So plant does not exist any damage But in the drought stress, when a large number of active oxygen free radicals that harm the structure and function of plant cells can not be cleared timely, the balance will be destroyed, leading to the accumulation of MAD, one of the ultimate products as a result of lipid peroxidation damage by free radicals. Chitosan can recognize and transmit the signal in plant. when identified, they induced
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Biodiversity Assessment of Sugar Beet Species and Its Wild Relatives: Linking Ecological Data with New Genetic Approaches

Biodiversity Assessment of Sugar Beet Species and Its Wild Relatives: Linking Ecological Data with New Genetic Approaches

Although the main research goals in sugar beet, deriv- ing from breeder’s interests and concerns, have been fo- cused on sugar content, beet yield, bolting control, seed quality, and pest and disease resistance, a growing atten- tion is being paid to other traits as a consequence of the future climatic changes. Even more so when the Medi- terranean is expected to be one of the most affected re- gions in the near future, with a substantial decrease in precipitation and a pronounced warming. The impact of drought has already been recognized as a major cause of yield losses in sugar beet [38,39], although the selection for increased drought tolerance has not been a breeding priority until recently [40]. Dry regions, such as those found in the South of Portugal, are outstanding areas to assess the degree of genotypic variation for drought re- sistance, across many types of environments, including the huge areas of salt marshes, and putative adaptations to soil salinity. Beyond the required deep knowledge of the genetic variability of the wild populations, the eco- logical characterization of their habitats per se, may in- dicate that a species possess appropriate physiological, ecological or behavioral adaptations to successfully colo- nize that particular environment. As a result, the wild beet species growing naturally in those environments will undoubtedly contribute with novel genes to sugar beet improvement for the “new” traits of interest.
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Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

One of the most promising applications of aqueous PEG-based models of osmotic stress is screening for potential drought-protective compounds. Substances that influence plant performance (without being plant protectants against biotic stress, e.g. from pathogens) in agrochemistry are defined as phytoeffectors-and include drought stress tolerance enhancers. Phytoeffectors are able to prime crop plants against a short-term drought and ensure sustaining their productivity under drought conditions with spatiotemporal control and largely independent of the crop species or variety used. Such effects were described for salicylic acid and its derivatives [65], as well as for various fungicides of the triazole [66] and imidacloprid family [67,68]. The drought-protective effects of small molecules on a plant organism are usually mediated by inhibition of enzymes, involved in plant response to stress, as it was described for poly(ADP-ribose) polymerase (PARP) in the beginning of this decade [68], although later at least direct involvement of PARP appeared doubtful [69]. If a molecular target for drought stress effects is known, and ideally the active site too, methods of computational chemistry like virtual screening and molecular docking approaches [70], allow to virtually screen thousands of structures with millions of conformers. The most promising candidates for wet lab testing can thus be identified.
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Selection of sorghum for drought tolerance in a semiarid environment

Selection of sorghum for drought tolerance in a semiarid environment

The trials in 2013 and 2014 were sowed in June and May respectively. When water was cut in stressed trials (late July and late June respectively), the temperatures in 2013 were much higher than in 2014, which explains, in part, the differences in the results (Figure 1). The stress under stressed condition in 2013 was greater than in 2014, resulting in a lower grain yield. Water stress reduced the grain yield by 68.9% in 2013, 31.2% in 2014 and 50.1% in the average of the two years. Reduction caused by water stress were also observed by Menezes et al. (2015), who found reductions of 39% in grain sorghum lines and by Batista et al. (2017), who found reductions of 35 and 65% in two years of evaluation in grain sorghum hybrids. Albuquerque et al. (2011) evaluated sorghum cultivars in a semi- arid region, obtaining an average yield of 1,710 kg ha -1 under low rainfall and 5,090 kg ha -1 under good rainfall conditions. Sorghum is a cereal tolerant to drought, when compared to maize and wheat, but when it is exposed to intense water deficit, mainly during flowering, grain yield is significantly reduced.
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Morpho-Physiological Characterization Related to Drought Tolerance of Common Bean (Phaseolus Vulgaris L.) Genotypes

Morpho-Physiological Characterization Related to Drought Tolerance of Common Bean (Phaseolus Vulgaris L.) Genotypes

Drought stress condition causes significant reduction on grain yield and biological yield of common bean (Tar’an and Singh, 2002). Direct selection for yield under favorable or water-limited conditions is the selection strategy that has been the most commonly used by crop breeders to improve yield in water-limited environments (Tilahun et al., 2004). Drought induces measures drought based on the loss of yield under drought tolerant genotypes. Drought susceptibility of a genotype is often measured as a function of the reduction in yield under drought stress. Drought stress affects the yield components such as number of pods per plant, number of seeds per pod, seed weight and harvest index (Ambachew et al., 2015; Darkwa et al., 2016).
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Physiological and Bio-Chemical Responses of Two Different Wheat Genotypes to Applied Salicylic Acid under Salt Stress

Physiological and Bio-Chemical Responses of Two Different Wheat Genotypes to Applied Salicylic Acid under Salt Stress

Turkiyalmaz (2012) argues in favor of these results that salt stress causes a drastic drop in root length and shoot’s height of wheat seedlings. But salicylic acid ameliorates the harmful effects of salinity and supports the plant to grow better under adverse sa- linity conditions. Waseem et al. (2006) alsofound the parallel results that application of salicylic acid to the soil improves the root growth and other physiological functions of wheat. These results are further support- ed by the findings of Szepesi et al. (2009) who report- ed that with the application of S.A under 100 mM NaCl in potato crop the root length was increased. Effect of salicylic acid on shoot length (cm)
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Effects of Climate Change and Drought-Stress on Plant Physiology

Effects of Climate Change and Drought-Stress on Plant Physiology

Global gene expression analysis showed a substantial down-regulation of many photosynthetic genes under pDr wilting drought compared with a subtle change under mDr In Arabidopsis, more than 50% of the photosynthate is stored as starch (Zeeman and Rees, 1999). Therefore, we examined the gene expression data for effects of both drought treatments on starch biosynthesis and degradation. Two enzymes in starch biodegradation, a-amylase and b-amylase, were induced under pDr with expression log2 ratios of 1.5 and 3, respectively. Under mDr, onlyb-amylase was induced, with a log 2 ratio of 0.4. To validate these observations, plants were sampled for starch quantification from both drought treatments. The highest accumulation of starch in wild type Arabidopsis plants was found to be in the late afternoon (at the end of the daily photoperiod; Caspar et al., 1985).
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