Estimation of Growth and Photosynthetic Performance of Two C₄ Species (<i>Pennisetum spicatum</i> (L.) Körn. and <i>Zea mays</i> L.) under a Low Temperature Treatment

Pearl millet (Pennisetum spicatum (L.) Körn.) and maize (Zea mays L.) are C₄ grass species grown for feeding humans and animals in Almadinah Almunawwarah, which is in the western part of Saudi Arabia. During the winter, the mean temperature, which drops to 14°C, represents a major problem for the growth of these species in this region. Therefore, the objectives of this research were to investigate the growth response and the photosynthetic performance of P. spicatum and Z. mays under a low temperature stress. The treatments involved daytime and nighttime temperatures of 14/12°C (low temperature) and 24/22°C (optimum temperature). The results indicated that low temperature significantly reduced all growth and physiological parameters, including seed germination, leaf expansion, leaf area, shoot length and root length of the two species compared to those of the control. Additionally, the low temperature significantly decreased the light-saturated assimilation rate (A_sat), quantum yield (ϕ), saturated rate of carbon dioxide uptake (A_max) and efficiency of carboxylation on both species compared to those of the control. Moreover, the values of Fv/Fm and the chlorophyll contents of both species were significantly reduced by low temperature compared to those of the control. It can be concluded that both species had little tolerance to low temperatures.     

Physiological and Biochemical Mechanisms of Salinity Tolerance in <i>Carex morrowii</i> Boott

Carex species are widely used in many parts of the world and contain a large number of ecologically diverse species. Among the Carex species, some of them are known to be glycophytes, while others are halophytes. Carex morrowii Boott (Cyperaceae) is resistant to trample through their root structure and has an essential ornamental value in the landscape with their leaves. However, no information was found about the level of salinity tolerance/ sensitivity of the Carex morrowii among these species. In the present study, changes in trace element contents (Na, K, Ca, Cu, Mn, Mg, Ni, Fe, P, Zn, and N) and their transport from roots to leaves, osmotic regulation, alterations in chlorophyll and carotenoid contents, nitrogen assimilation (nitrate reductase activity; NRA) and total soluble protein content in both roots and leaves of Carex morrowii under different salinity concentrations (50 mM, 100 mM, 200 mM and 300 mM NaCl) were examined in detail. Our study provides the first detailed data concerning the responses of leaves and roots and the determination of the level of salinity tolerance/sensitivity of the Carex morrowii. The K+ /Na+ ratio was preserved up to 200 mM NaCl, and accordingly, the element uptake and transport ratios showed that they could control moderate NaCl levels. Ca homeostasis that is maintained even in 200 mM NaCl concentration can be effective in maintaining the structural integrity and selective permeability of the cell membranes, while 300 mM NaCl concentration caused decreased photosynthetic pigments, and deterioration in element content and compartmentation. Moreover, these data suggest that plant parts of Carex morrowii respond differently against varied levels of salinity stress. Although the decrease in NR activity at 200 mM and 300 mM NaCl concentrations in the leaves, NR activity was maintained in the roots. Consequently, Carex morrowii is moderately tolerant to salinity and the carotenoid content and osmotic regulation of Carex morrowii appears to be instrumental in its survival at different salinity levels. Especially the roots of Carex morrowii have a remarkable role in salinity tolerance.     

Photosynthetic Behaviour and Mineral Nutrition of <i>Tamarix gallica</i> Cultivated Under Aluminum and NaCl Combined Stress

The lack of knowledge of plant tolerance and differential response to aluminum (Al) encouraged many researchers, in the last decade, to elucidate Al toxicity and tolerance mechanisms. The current study reported the impact of Al, a toxic element with negative effects on plant growth and development, in halophytic plant Tamarix gallica. Plants were subjected to different Al concentrations (0, 200, 500 and 800 μM) with or without NaCl (200 mM) supplementation. Growth, photosynthesis and mineral content were assessed. Al stress had a significant decrease on shoots’ biomass production between 19 to 41%, and a little variation on chlorophyll content and photosynthetic efficiency (Fo, Fm, Fv fluorescence’s and Fv/Fm). Furthermore, the Al-treatments did not affect significantly the content of potassium, calcium, and magnesium in different plant parts, whereas NaCl addition to the medium induced a decrease in these elements’ concentrations. Our results have shown that T. gallica is able to accumulate the high levels of Al in shoots and roots, 6288 μg.g^-1 DW and 7834 μg.g^-1 DW respectively. It is considered as a hyperaccumulator plant of Al. In addition, Na⁺ contents in shoots and roots exceed 23000 μg.g^-1 DW. Therefore, T. gallica presents a high tolerance at the same time to Al and NaCl phytotoxicity, so it is interesting to use in phytoremediation programs.     

Physiological Responses of <i>Dendrobium officinale</i> under Exposure to Cold Stress with Two Cultivars

This study aimed to explore the cold tolerance of two cultivars of Dendrobium officinale (MG1, MG2) grown in different regions of China. Under -2°C incubation, cultivar MG1 remained active after 3 d, and continued to grow after returning to room temperature. However, MG2 could only maintain its activity after 2 d treatment at −2°C, and the seedlings died with the low temperature treatment time. Investigation of the characteristics of the plants grown in the south (Hangzhou) or north (Zhengzhou) of China indicated that the leaves of MG1 also had reduced stomatal density, the highest thickness, and a compact microstructure. The contents of proline and soluble sugars were higher in MG1 than those in MG2. The cultivar MG1 had higher SOD enzyme activity than MG2, while CAT and POD activities in samples from Zhengzhou were higher than those from Hangzhou. The contents of polysaccharides and alkaloids in stems of in MG1 were higher than those in MG2, while the content of flavonoids in the Zhengzhou samples was higher than that in the Hangzhou samples. In addition, plant heights, stem diameters, and chlorophyll content were higher in MG1. Overall, MG1 had better cold resistance than MG2. MG1 is a cold tolerant cultivar with thick leaves and reduced stomatal density, higher contents of soluble sugars, proline, CAT, POD, polysaccharides, flavonoids and alkaloids, which together make it more adaptable to low temperatures. Thus, the cultivar MG1, with its demonstrated cold tolerance, can accordingly be grown on a large scale in cold regions, thereby expanding the available planting area for this important traditional medicinal plant to meet the increasing commercial demand for it.     

Arbuscular mycorrhiza influences carbon‐use efficiency and grain yield of wheat grown under pre‐ and post‐anthesis salinity stress

• Soil salinity severely affects and constrains crop production worldwide. Salinity causes osmotic and ionic stress, inhibiting gas exchange and photosynthesis, ultimately impairing plant growth and development. Arbuscular mycorrhiza (AM) have been shown to maintain light and carbon use efficiency under stress, possibly providing a tool to improve salinity tolerance of the host plants. Thus, it was hypothesized that AM will contribute to improved growth and yield under stress conditions.
• Wheat plants (Triticum aestivum L.) were grown with (AMF+) or without (AMF?) arbuscular mycorrhizal fungi (AMF) inoculation. Plants were subjected to salinity stress (200 mm NaCl) either at pre‐ or post‐anthesis or at both stages. Growth and yield components, leaf chlorophyll content as well as gas exchange parameters and AMF colonization were analysed.
• AM plants exhibited a higher rate of net photosynthesis and stomatal conductance and lower intrinsic water use efficiency. Furthermore, AM wheat plants subjected to salinity stress at both pre‐anthesis and post‐anthesis maintained higher grain yield than non‐AM salinity‐stressed plants.
• These results suggest that AMF inoculation mitigates the negative effects of salinity stress by influencing carbon use efficiency and maintaining higher grain yield under stress.

     

<i>In vitro</i> Evaluation of Seed Germination in Twelve Alfalfa Cultivars under Salt Stress

Alfalfa (Medicago sativa L.), when exposed to abiotic stress such as salinity, suffers significant losses in yield and productivity. The present study evaluated the salinity tolerance of 12 alfalfa cultivars in vitro using five concentrations of sodium chloride (NaCl), ranging from 0 to 250 mmol L⁻¹ . The results obtained in the current study revealed that the Saudi cultivars, Kasimi and Hassawi, and the German cultivar (Berlin) had the highest salinity tolerance in terms of germination percentage (GP), corrected germination rate index (CGRI), days to reach 50% germination (GT50), and ability to form cotyledonary and true leaves. Under mmol L⁻¹ NaCl, the Saudi cultivar Kasimi cultivar showed GP, CGRI, and GT50 of 55.20%, 123.15, and 3.77 days, respectively. Similarly, the German cultivar (Berlin) showed GP, CGRI, and GT50 of 50.06%, 86.61, and 5.17 days, respectively. These findings might reveal a pivotal aspect in salt tolerance in alfalfa. Our results will help to select salt-tolerant alfalfa cultivars that could thrive in arid and semi-arid areas with salinity problems.     

Physiological and Biochemical Mechanisms of Exogenous Calcium Chloride on Alleviating Salt Stress in Two Tartary Buckwheat (<i>Fagopyrum tataricum</i>) Varieties Differing in Salinity Tolerance

Salt stress is one of the most serious abiotic stresses limiting plant growth and development. Calcium as an essential nutrient element and important signaling molecule plays an important role in ameliorating the adverse effect of salinity on plants. This study aimed to investigate the impact of exogenous calcium on improving salt tolerance in Tartary buckwheat cultivars, cv. Xinong9920 (salt-tolerant) and cv. Xinong9909 (salt-sensitive). Four-week-old Tartary buckwheat seedlings under 100 mM NaCl stress were treated with and without exogenous calcium chloride (CaCl₂), Ca²⁺ chelator ethylene glycol tetraacetic acid (EGTA) and Ca²⁺-channel blocker lanthanum chloride (LaCl₃) for 10 days. Then, some important physiological and biochemical indexes were determined. The results showed that salt stress significantly reduced seedling growth, decreased photosynthetic pigments, inhibited antioxidants and antioxidant enzyme activities. However, it increased the reactive oxygen species (ROS) levels in the two Tartary buckwheat cultivars. Exogenous 10 mM CaCl₂ application on salt-stressed Tartary buckwheat seedlings obviously mitigated the negative effects of NaCl stress and partially restored seedlings growth. Ca²⁺-treated salt-stressed seedlings diplayed a suppressed accumulation of ROS, increased the contents of total chlorophyll, soluble protein, proline and antioxidants, and elevated the activities of antioxidant enzymes compared with salt stress alone. On the contrary, the addition of 0.5 mM LaCl₃ and 5 mM EGTA on salt-stressed Tartary buckwheat seedlings exhibited the opposite effects to those with CaCl₂ treatment. These results indicate that exogenous Ca²⁺ can enhance salt stress tolerance and Ca²⁺ supplementation may be an effective practice to cultivate Tartary buckwheat in saline soils.     

Ameliorating effect of triacontanol on salt stressederythrina variegata seedlings. Changes in growth,biomass, pigments and solute accumulation

Erythrina variegata Lam. seedlings were grown under low (100 mM NaCl) and high (250 mM NaCl) salinity. Seedlings exposed to high salinity for 10 d showed significant reduction in growth rate and biomass production while the root/shoot ratio increased. In contrast to pigment and protein contents, starch and saccharide contents increased in salt stressed seedlings. When the seedlings were subsequently sprayed with triacontanol (1 mg kg^-1) the salinity effect was partially ameliorated and growth, biomass, chlorophyll and carotenoid contents increased.     

Changes in photosynthetic pigments and chlorophyll-<Emphasis Type="Italic">a</Emphasis> fluorescence attributes of sweet-forage and grain sorghum cultivars under salt stress

Water shortage leads to a low quality of water, especially saline water in most parts of agricultural regions. This experiment was designed to determine the effects of saline irrigation on sorghum as a moderately salt-tolerant crop. To study salinity effects on photosynthetic pigment attributes including the chlorophyll content and chlorophyll fluorescence, an experiment was performed in a climate-controlled greenhouse at two vegetative and reproductive stages. The experimental design was factorial based on a completely randomized design with five NaCl concentrations (control, 50, 100, 150, and 200 mM), two grain and sweet-forage sorghum cultivars (Kimia and Pegah, respectively) and four replications. According to the experimental data, there were no significant differences between two grain and sweet-forage cultivars. Except for 100 and 150 mM NaCl, salinity significantly decreased the chlorophyll index and pigment contents of the leaf, while it increased the chlorophyll-a fluorescence characteristics. Although salinity reduced photosynthetic pigments and the crop yield, either grain or sweet-forage cultivars could significantly control the effect of salinity between 100 and 150 mM NaCl at both developmental stages, showing the possibility of using saline water in sorghum cultivation up to 150 mM NaCl.     

Menadione sodium bisulphite regulates physiological and biochemical responses to lessen salinity effects on wheat (Triticum aestivum L.)

Salinity is a significant constraint for plant survival and productivity. Therefore, an immediate solution to this problem is sought to meet the human population''s food demands. Recently, Menadione sodium bisulphite (MSB) has emerged as a significant regulator of plant defense response under abiotic stress. Studies on MSB are scarce, and a few reports on salinity (Arabidopsis and okra) and cadmium stress (okra) are present in the literature. However, these studies did not include the impact of MSB on physiological and plant water relation attributes, critical mediators of plant survival, and yield production under stress. Our results studied the impact of MSB on wheat administered to NaCl salinity in hydroponics medium. We used two wheat cultivars (salt-sensitive MH-97 and salt-tolerant Millat-2011, based on our pre-experimental studies). Seeds were primed in different MSB doses [control (unprimed), hydroprimed, 5, 10, 20, and 30 mM]. Salinity significantly diminished growth, chlorophyll molecules, photosynthesis, total free amino acids, water and turgor potentials, K, Ca, and P contents of wheat when administered NaCl salinity in the nutrient solution. Besides, a noteworthy accretion was present in oxidative stress markers [hydrogen peroxide & malondialdehyde], proline, ascorbic acid, antioxidant enzyme activities, and Na⁺ accumulation under salinity. Moreover, MSB noticeably enhanced chlorophyll molecules, proline, and oxidative defense to improve photosynthesis, plant water relations, and diminish specific ions toxicity. Our results manifested better defense regulation in salt-administered plants primed with 5 and 10 mM MSB. Our findings strongly advocated the use of MSB in improving plant salinity tolerance, particularly in wheat.     

Effects of Two Potential Allelochemicals on the Photosystem II of <i>Nitzschia closterium</i> and<i> Monostroma nitidum</i>

In aquaculture, high-density seaweed farming brings higher economic benefits but also increases outbreaks of diatom felt. The effective control of diatom felt in high-density seaweed farming has always been a research hotspot. This study selected two potential allelochemicals 2-hydroxycinnamic acid and quinic acid to explore their effects on a diatom Nitzschia closterium and an economic seaweed Monostroma nitidum. The results showed that 2-hydroxycinnamic acid had better inhibitory effects than quinic acid on the growth, pigment content and photosynthetic efficiency of N. closterium. Their half-maximal inhibitory concentrations at 120 h (IC_{50–120 h}) were 0.9000 and 1.278 mM, respectively. Additionally, these allelochemicals had limited inhibitory effects on the growth, pigment content and photosynthetic efficiency of M. nitidum before 24 h. To further explore the allelopathic effect of these chemicals, this study focused on the photosystem II energy fluxes of N. closterium. It was found that 3 mM 2-hydroxycinnamic acid could destroy the whole photosynthetic system by devastating the PSII reaction centre (RC) before 24 h; however, the same concentration of quinic acid could only down-regulate the electron transport efficiency by changing the effective antenna size of an active RC and downregulating the PSII reaction centre density. These experimental results are expected to provide a new strategy to control diatom felt blooms on the high-density seaweed farming areas.     

Germination and Photosynthetic Responses to Salinity and Alkalinity in <i>Avicenna marina</i> Propagules

Avicenna marina (Forssk.) Vierh is a halophytic mangrove. The reproductive unit is green and has photosynthetic propagules. Mangroves are naturally exposed to fluctuations in some abiotic factors at the soil surface, including salinity and alkalinity. The objective of this study was to determine the effects of two salts including NaCl and NaHCO₃ on germination processes and discuss the relationships between cotyledon photosynthesis and embryo axis growth in A. marina propagules. These propagules came from Al Birk, located on the shoreline of the Saudi Red Sea. The results showed that the studied salts did not affect neither the final germination percentage nor the embryo axis growth. However, rooting and root growth were delayed by both salts at 300 mM and were strongly inhibited by 600 mM NaHCO₃. Both NaCl and NaHCO₃ reduced the photosynthetic activity. These two salts did not affect the other photosynthetic parameters, including stomatal conductance, net transpiration, and intercellular CO₂. Thereafter, the reduction in net photosynthesis was not related to any limitation of stomatal conductance. The early germination phase was independent of cotyledon photosynthesis, whereas rooting and root growth may be limited by reduced photosynthesis under NaCl and NaHCO₃.     

Composted sewage sludge can improve the physiological properties of<Emphasis Type="Italic">Betula schmidtii</Emphasis> grown in tailings

We investigated how the application of composted sewage sludge to tailings affects the physiological response of woody plants growing on abandoned coal-mining sites. Twenty seedlings ofBetula schmidtii were transplanted to pots containing various combinations of artificial soil plus nursery soil, tailings, composted soil, or tailings amended with composted soil. Dry weights, shoot to root ratios, relative growth rates (RGR), chlorophyll content and fluorescence, and carbohydrate concentrations were assessed at the end of the experiment. Growth responses differed significantly among soil types. For example, dry weights were greatest for seedlings grown in composted soil and smallest for plants raised in pure tailings. Shoot to root ratios were higher for seedlings in composted soil compared with those in either tailings or nursery soil. Leaf chlorophyll content was twice as high for seedlings from composted soil than for those in the nursery soil or tailings; chlorophyll fluorescence (Fv/Fm) was lower for seedlings in either nursery soil or tailings than for those in composted soil. In contrast, plants grown in either nursery soil or tailings had higher starch concentrations in their stems, whereas the carbohydrate allocation of seedlings in composted soil was highest in the leaves, followed by stems and roots. Overall, the carbohydrate content was highest in the leaves, except for seedlings treated with tailings. Therefore, we believe that composted soil can improve the physiological and biochemical properties of trees growing in tailings when appropriate nutrients are supplemented.     

Salt Stress Affects the Growth and Yield of Wheat (<i>Triticum aestivum</i> L.) by Altering the Antioxidant Machinery and Expression of Hormones and Stress-Specific Genes

Understanding physiological responses in saline agriculture may facilitate wheat breeding programs. Based on a screening test, the Ningmai-14 (NM-14) and Yangmai-23 (YM-23) wheat cultivars were selected for further experiments to understand the underlying salinity tolerance mechanism. This study investigated the effects of five salinity levels such as Control (CK) = 0 (without NaCl stress), S1 = 0.20%, S2 = 0.25%, S3 = 0.30% and S4 = 0.35% of NaCl concentrations of soil on wheat plants. The results showed that increased salinity concentration reduced the growth and yield of wheat cultivars (NM-14 and YM-23). However, YM-23 (12.7%) yielded more than NM-14 at maximum salinity stress. The higher salinity (S4) increased the concentration of Na⁺ (4.3 to 5.8-fold) and P contents (2.5 to 2.2-fold), while reducing the average concentrations of K⁺, Cu, and K⁺/Na⁺ ratio. The higher salinity (S4) reduced the spikelet length by 21.35% (followed by grain spike⁻¹), and the starch content by 18.81%. In the YM-23 cultivar, higher salinity increased superoxide dismutase (SOD), total antioxidant capacity (TAC), and amylase. Compared to NM-14, induced expression of TaYUC2, 6, and TaGA13ox, 20ox genes were recorded in YM-23. Similarly, in YM-23 the stress-specific genes such as TaHSP70, 90 were enhanced whereas, TaSOS1, 2 were suppressed. Overall, our study revealed that salt tolerant cultivars modulate hormonal and antioxidant activities, thus maintaining high growth.

     

AM Fungi and <i>Piriformospora indica</i> Improve Plant Growth of <i>Pinus elliottii</i> Seedlings

Pinus elliottii is an exotic afforestation pine extensively distributed in southern parts of China. In order to understand whether endophytic fungi can affect seedling growth of P. elliottii, Piriformospora indica (Pi), Funnelifcrmis mosseae (Fm), and Diversispora tortuosa (Dt) were inoculated respectively, and the non-inoculated group was set as control. The growth indexes, the contents of soluble sugar and soluble protein, and plant endogenous hormone levels in the leaves of P. elliottii, were analyzed. The results showed that Fm, Dt and Pi colonized the P. elliottii roots to form mycorrhizal structure and chlamydospores arranged in beads respectively. Three fungal inoculants exhibited the stimulated growth responses, whilst Dt illustrated the most positive effect on plant height, single fresh weight, trunk diameter and root system structure, compared with the control. On the other hand, the soluble sugar and soluble protein contents were increased distinctively in mycorrhizal plants. The endogenous IAA, GA3, ZR contents were increased, while the ABA contents were reduced in mycorrhizal plants versus non-mycorrhizal plants. The fungi-induced endogenous hormone changes triggered plant growth improvement of P. elliottii seedlings. This research unraveled the positive effect of AM fungi and P. indica on growth of pine seedlings, while, more application of endophytic fungi to fields needs to be explored.     

Temperature and salinity regulation of growth and gas exchange of Salicornia fruticosa (L.) L.

Summary Salicornia fruticosa was collected from a salt marsh on the Mediterranean sea coast in Libya. Growth and gas exchange of this C₃ species were monitered in plants pretreated at various NaCl concentrations (0, 171, 342, 513 and 855 mM). Maximum growth was at 171 mM NaCl under cool growth conditions (20/10° C) and at 342 mM NaCl under warm growth conditions (30/15° C) with minimum growth at 0 mM NaCl (control). Net photosynthesis (Pn) was greatest in plants grown in 171 mM NaCl with plants grown at 513 and 855 mM having lowest rates. Maximum Pn was at 20–25° C shoot temperatures with statistically significant reductions at 30° C in control plants while salt treated plants showed such reductions at 35° C. Salt treatments increased dark respiration over the control at 171 and 342 mM but reduced it at higher concentrations. Photorespiration was reduced by salt treatment and increased by increasing shoot temperature. Greatest transpiration was in 171 mM NaCl treated plants and increasing shoot temperature increased transpiration in all treatments. Stomatal resistance to CO₂ influx was influenced only moderately by temperature while increasing salinity resulted in increased stomatal resistance. In general both temperature and salinity increased the mesophyll resistance to CO₂ influx. The species seems adapted to the warm saline habitat along the Mediterranean sea coast, at least partially, by its ability to maintain relatively high Pn at moderate NaCl concentrations over a broad range of shoot temperatures.     

Genome-Wide Identification and Expression Profiling Suggest that Invertase Genes Function in Silique Development and the Response to <i>Sclerotinia sclerotiorum</i> in <i>Brassica napus</i>

Invertase (INV), a key enzyme in sucrose metabolism, irreversibly catalyzes the hydrolysis of sucrose to glucose and fructose, thus playing important roles in plant growth, development, and biotic and abiotic stress responses. In this study, we identified 27 members of the BnaINV family in Brassica napus. We constructed a phylogenetic tree of the family and predicted the gene structures, conserved motifs, cis-acting elements in promoters, physicochemical properties of encoded proteins, and chromosomal distribution of the BnaINVs. We also analyzed the expression of the BnaINVs in different tissues and developmental stages in the B. napus cultivar Zhongshuang 11 using qRT-PCR. In addition, we analyzed RNA-sequencing data to explore the expression patterns of the BnaINVs in four cultivars with different harvest indices and in plants inoculated with the pathogenic fungus Sclerotinia sclerotiorum. We used WGCNA (weighted coexpression network analysis) to uncover BnaINVregulatory networks. Finally, we explored the expression patterns of several BnaINV genes in cultivars with long (Zhongshuang 4) and short (Ningyou 12) siliques. Our results suggest that BnaINVs play important roles in the growth and development of rapeseed siliques and the defense response against pathogens. Our findings could facilitate the breeding of high-yielding B. napus cultivars with strong disease resistance.     

Light Intensity Affects the Coloration and Structure of Chimeric Leaves of <i>Ananas comosus</i> var<i>. bracteatus</i>

Ananas comosus var. bracteatus is an important ornamental plant because of its green/white chimeric leaves. The accumulation of anthocyanin makes the leaf turn to red especially in the marginal part. However, the red fades away in summer and winter. Light intensity is one of the most important factors affecting leaf color along the seasons. In order to understand the effects of light intensity on the growth and coloration of the chimeric leaves, Ananas comosus var. bracteatus was grown under full sunlight, 50% shade and 75% shade for 75 days to evaluate the concentration of pigments, the color parameters (values L*, a*, b*) and the morpho-anatomical variations of chimeric leaves. The results showed that a high irradiance was beneficial to keep the chimeric leaves red. However, prolonged exposure to high irradiance caused a damage, some of the leaves wrinkled and even burned. Shading instead decreased the concentration of anthocyanin and increased the concentration of chlorophyll, especially in the white marginal part of the leaves. Numerous chloroplasts were observed in the mesophyll cells of the white marginal part of the chimeric leaves under shading for 75 days. The increase in chlorophyll concentration resulted in a better growth of plants. In order to balance the growth and coloration of the leaves, approximately 50% shade is suggested to be the optimum light irradiance condition for Ananas comosus var. bracteatus in summer.     

Antibacterial Activity and Mechanisms of Ethanol Extracts from <i>Scutellaria baicalensis</i> Georgi and <i>Magnolia officinalis</i> against <i>Phytophthora nicotianae</i>

Phytophthora nicotianae causes substantial economic losses in most countries where tobacco is produced. At present, the control of P. nicotianae mainly depends on chemical methods, with considerable environmental and health issues. We investigated the effects of ethanol extracts from Scutellaria baicalensis Georgi (SBG) and Magnolia officinalis (MO). On mycelial growth, sporangium formation, and zoospore release of P. nicotianae. Both extracts inhibited the growth of P. nicotianae, with mycelial growth inhibition rates of 88.92% and 93.92%, respectively, at 40 mg/mL, and EC50 values of 5.39 and 5.74 mg/mL, respectively. The underlying mechanisms were the inhibition of sporangium formation, the reduction of zoospore number, and the destruction of the mycelium structure. At an SBG extract concentration of 16.17 mg/mL, the inhibition rates for sporangia and zoospores were 98.66% and 99.39%, respectively. At an MO extract concentration of 2.87 mg/mL, the production of sporangia and zoospores was completely inhibited. The hyphae treated with the two plant extracts showed different degrees of deformation and damage. Hyphae treated with SBG extract showed adhesion and local swelling, whereas treatment with MO extract resulted in broken hyphae. Mixture of the extracts resulted in a good synergistic effect.