大刍草稀有等位基因促进玉米密植高产

密植是提高作物单位面积产量、促进粮食增产的重要途径之一。叶夹角是影响玉米(Zea mays)密植的关键因子。中国农业大学田丰课题组最近克隆了2个调控玉米叶夹角的数量性状位点(QTL)——UPA1和UPA2, 揭示了这2个位点的功能基因(brd1和ZmRAVL1)通过油菜素内酯(BR)信号通路调控叶夹角。UPA2位于ZmRAVL1上游9.5 kb, 可与DRL1蛋白结合。另一个影响玉米叶夹角的蛋白LG1可以激活ZmRAVL1的表达; DRL1蛋白与LG1蛋白直接互作抑制LG1对ZmRAVL1的激活表达。玉米祖先种大刍草(teosinte)的UPA2位点序列与DRL1蛋白结合能力更强, 导致大刍草ZmRAVL1的表达受到更强的抑制, 下调表达的ZmRAVL1进一步使下游基因brd1的表达下调, 进而降低叶环区的内源BR水平, 导致叶夹角变小。将大刍草的UPA2等位基因导入到玉米中或对玉米中ZmRAVL1进行基因编辑, 在密植条件下均可显著提高玉米产量。上述发现为高产玉米品种的分子育种改良提供了重要理论基础和基因资源。     

大刍草稀有等位基因促进玉米密植高产

密植是提高作物单位面积产量、促进粮食增产的重要途径之一。叶夹角是影响玉米(Zea mays)密植的关键因子。中国农业大学田丰课题组最近克隆了2个调控玉米叶夹角的数量性状位点(QTL)——UPA1和UPA2, 揭示了这2个位点的功能基因(brd1和ZmRAVL1)通过油菜素内酯(BR)信号通路调控叶夹角。UPA2位于ZmRAVL1上游9.5 kb, 可与DRL1蛋白结合。另一个影响玉米叶夹角的蛋白LG1可以激活ZmRAVL1的表达; DRL1蛋白与LG1蛋白直接互作抑制LG1对ZmRAVL1的激活表达。玉米祖先种大刍草(teosinte)的UPA2位点序列与DRL1蛋白结合能力更强, 导致大刍草ZmRAVL1的表达受到更强的抑制, 下调表达的ZmRAVL1进一步使下游基因brd1的表达下调, 进而降低叶环区的内源BR水平, 导致叶夹角变小。将大刍草的UPA2等位基因导入到玉米中或对玉米中ZmRAVL1进行基因编辑, 在密植条件下均可显著提高玉米产量。上述发现为高产玉米品种的分子育种改良提供了重要理论基础和基因资源。     

Enhanced Nitrogen Fixation Increases Net Photosynthetic Output and Seed Yield of Hydroponically Grown Soybean

Ten to 20% of the net photosynthetic output of a tropical grainlegume may be consumed by the nodulation-nitrogen-fixation process.If plant growth activities during the reproductive phase werelimited by photosynthetic output, enhanced nitrogen fixationwould seemingly lower total plant mass and seed yield. To testthis possibility, soybean [Glycine max (L.) Merr.] plants weregrown hydroponically on nutrient medium supplemented with minimalurea or with an excess of either nitrate or nitrate plus urea.Acetylene reduction activities (i.e. nitrogen fixation rates)and transpiration rates were measured twice weekly on theseplants through pod fill. Of the plants inoculated, those grownon minimal urea revealed significantly greater acetylene reductionactivities and transpiration rates. At maturity, plants thathad fixed nitrogen at a rapid rate during pod fill had a significantlygreater seed size, total plant mass (i.e. net photosyntheticrate) and nitrogen content than uninoculated or poorly nodulatedplants grown on an excess of nitrate. It is concluded, therefore,that a rapid rate of nitrogen fixation during pod fill enhancesboth transpiration and net photosynthetic output. The increasedavailability of usable nitrogen (i.e. ureides), coupled withenhanced transpiration and photosynthetic output, significantlyincreases total plant mass and seed yield. Thus, enhanced nitrogenfixation seems to be an inexpensive means of increasing seedyield of soybean and perhaps of other tropical grain legumes. Key words: Glycine max, nodulation, nitrate, urea     

Exogenous Application of Melatonin Induces Tolerance to Salt Stress by Improving the Photosynthetic Efficiency and Antioxidant Defense System of Maize Seedling

Journal of Plant Growth Regulation - Melatonin is a ubiquitous signaling plant hormone that plays a crucial role in regulating the growth and development of plants under stress conditions. Since a...     

The On-Line Estimation of Yield and Photosynthetic Efficiency of Photoheterotrophic Plant Cells (Ocimum basilicum)

The yield (gramme bioproduct gramme^–1 sugar consumed)of plant cells increases on transition from heterotrophic tophotoheterotrophic nutrition and when specific growth rate increases.There are several advantages in using gas analysis to estimateyield over other methods involving wet chemistry. However, applyinggas analysis to reactions involving plant cells is not withoutdifficulty, in particular that of measuring the small differencein partial pressure of carbon dioxide or oxygen between thegas inlet and outlet of the reactor. The experience of the workreported here is that difficulties such as this can be overcomeby using accurate gas analysers and by carefully calibratingthem. In this paper the theory of material balancing is applied tothe growth of higher plant cells (Ocimum basilicum L. sweetbasil) in culture. Three equations are derived relating yieldeither to the rate of carbon dioxide produced, the rate of oxygenconsumed, or their ratio. The validity of these equations andtheir underlying assumptions are tested by comparing yieldsin continuous cultures based on wet chemistry to yields basedon gas analysis. Generally similar yield values were obtainedand these varied between 0.65 and 0.96. Making further assumptions, the analysis was extended to estimatephotosynthetic efficiency in photoheterotrophic conditions.Photosynthetic efficency varied from 0% to 5% and increasedin the following circumstances: on transition from phosphateto fructose limitation and when fructose concentration in thefresh medium was decreased, when specific growth rate was increaseduntil a critical value of 0.64 of the maximum specific growthrate was reached. Although absolute values of photosyntheticefficiency were not verified, the relative changes agreed withother measurements of photosynthetic development (i.e. specificproduction rate of chlorophyll and actual photosynthesis rateunit_–1 dry biomass). Key words: Continuous culture, Gas analysis, Photosynthetic efficiency, Ocimum basilicum.     

Interactive Effects of Elevated CO2 Concentration and Irrigation on Photosynthetic Parameters and Yield of Maize in Northeast China

Maize is one of the major cultivated crops of China, having a central role in ensuring the food security of the country. There has been a significant increase in studies of maize under interactive effects of elevated CO₂ concentration ([CO₂]) and other factors, yet the interactive effects of elevated [CO₂] and increasing precipitation on maize has remained unclear. In this study, a manipulative experiment in Jinzhou, Liaoning province, Northeast China was performed so as to obtain reliable results concerning the later effects. The Open Top Chambers (OTCs) experiment was designed to control contrasting [CO₂] i.e., 390, 450 and 550 µmol·mol⁻¹, and the experiment with 15% increasing precipitation levels was also set based on the average monthly precipitation of 5–9 month from 1981 to 2010 and controlled by irrigation. Thus, six treatments, i.e. C₅₅₀W_+15%, C₅₅₀W₀, C₄₅₀W_+15%, C₄₅₀W₀, C₃₉₀W_+15% and C₃₉₀W₀ were included in this study. The results showed that the irrigation under elevated [CO₂] levels increased the leaf net photosynthetic rate (P _n) and intercellular CO₂ concentration (C _i) of maize. Similarly, the stomatal conductance (G _s) and transpiration rate (T _r) decreased with elevated [CO₂], but irrigation have a positive effect on increased of them at each [CO₂] level, resulting in the water use efficiency (WUE) higher in natural precipitation treatment than irrigation treatment at elevated [CO₂] levels. Irradiance-response parameters, e.g., maximum net photosynthetic rate (P _nmax) and light saturation points (LSP) were increased under elevated [CO₂] and irrigation, and dark respiration (R _d) was increased as well. The growth characteristics, e.g., plant height, leaf area and aboveground biomass were enhanced, resulting in an improved of yield and ear characteristics except axle diameter. The study concluded by reporting that, future elevated [CO₂] may favor to maize when coupled with increasing amount of precipitation in Northeast China.     

玉米、花生及其间作茬口与施磷对冬小麦光合特性及产量的影响机制

该试验在玉米单作茬口、玉米-花生间作茬口(间作茬口)、花生单作茬口共3种茬口,以及0 kg P_2O_5·hm~(-2)(P_0)和180 kg P_2O_5·hm~(-2)(P_1) 2个磷水平下,研究了间作茬口与施磷对冬小麦分蘖、叶面积指数(LAI)、干物质积累、光合特性及产量的影响机制,为玉米花生间作与小麦-玉米复种轮作提供理论依据。结果表明:(1)间作茬口较玉米茬口显著提高了冬小麦有效分蘖数、LAI、净光合速率和干物质积累量,并提高了冬小麦旗叶的SPAD值、CO_2饱和点、光饱和点及最大净光合速率(P_(nmax))、表观量子效率(AQY)、羧化效率(CE)、最大羧化速率(V_(cmax))、最大RUBP再生的电子传递速率(J_(max))和最大磷酸丙糖利用速率(V_(TPU)),且CE、V_(cmax)、V_(TPU)的增幅均达到显著水平(P0.05),有效改善了冬小麦产量构成,显著提高籽粒产量(P0.05)。(2)间作茬口较花生茬口提高了冬小麦乳熟期的P_(nmax)、AQY、CE,增加了穗粒数和粒重,提高了产量。(3)与不施磷相比,施磷180 kg P_2O_5·hm~(-2)显著促进间作茬口冬小麦生长,显著提高冬小麦旗叶的SPAD值、P_(nmax)、AQY、CE、V_(cmax)、J_(max)、V_(TPU)和籽粒产量(P0.05)。研究发现,间作茬口较玉米茬口能有效增强冬小麦旗叶表观量子效率和CO_2羧化能力,显著提高小麦花后光合能力,促进冬小麦生长,从而增加穗粒数、粒重和籽粒产量,且间作茬口结合施磷180 kg P_2O_5·hm~(-2)效果更好。     

Salicylic Acid-Mediated Enhancement of Photosynthesis Attributes and Antioxidant Capacity Contributes to Yield Improvement of Maize Plants Under Salt Stress

Journal of Plant Growth Regulation - Addressing salinity-induced crop losses is a prime concern of modern agriculture to sustain agricultural productivity, thereby contributing to global food...     

Photosynthetic Capacity and Nitrogen Use Efficiency of Maize, Wheat, and Rice: A Comparison Between C3 and C4 Photosynthesis

The C₃ species wheat and rice and the C₄ species maize weregrown for 2–3 weeks in controlled environment growth chambersat 20 or 30 °C day and 15 °C night temperatures. CO₂assimilation rates (at 20 and 30 °C) and several leaf parametersincluding total nitrogen, soluble protein, and RuBP carboxylaseprotein were determined. When the assimilation rates under atmosphericCO₂ and O₂ levels were expressed on a total nitrogen basis (=nitrogen use efficiency), the C₄ species maize had a greaternitrogen use efficiency than either of the two C₃ species examined,regardless of the combination of temperatures used for growthor measurement of CO₂ assimilation. Maize is also shown to makemore efficient use of its soluble protein and RuBP carboxylaseprotein than either wheat or rice when measurements are madeat 320 parts 10^–6 CO₂ and 21% O₂. Atmospheric CO₂ enrichmentduring CO₂ assimilation measurements increased the nitrogenuse efficiency in the C₃ species. In one treatment (wheat grownand measured at 20 °C), CO₂ assimilation under saturatingCO₂ showed nitrogen, soluble protein, and RuBP carboxylase proteinuse efficiencies equal to or greater than that of the C₄ species. These data indicate that C4 species may make more efficientuse of their nitrogen, soluble protein, and RuBP carboxylaseprotein than C₃ species under atmospheric CO₂ conditions. Thismay be due in part to the C₄ cycle and CO₂-concentrating mechanismin C₄ photosynthesis.     

Canopy Apparent Photosynthetic Characteristics and Yield of Two Spike-Type Wheat Cultivars in Response to Row Spacing under High Plant Density

In northern China, large-spike wheat (Triticum aestivum L) is considered to have significant potential for increasing yields due to its greater single-plant productivity despite its lower percentage of effective tillers, and increasing the plant density is an effective means of achieving a higher grain yield. However, with increases in plant density, the amount of solar radiation intercepted by lower strata leaves is decreased and the rate of leaf senescence is accelerated. Row spacing can be manipulated to optimize the plant spatial distribution under high plant density, therefore improving light conditions within the canopy. Consequently, field experiments were conducted from 2010 to 2012 to investigate whether changes in row spacing under high plant density led to differences in canopy apparent photosynthesis (CAP), individual leaf photosynthesis and grain yield. Two different spike-type winter wheat cultivars, Jimai22 (a small-spike cultivar as a control cultivar) and Wennong6 (a large-spike cultivar), were grown at a constant plant density of 3,600,000 plants ha^–1 (a relatively higher plant density) over a wide range of row spacing as follows: 5-cm row spacing (R₀), 15-cm row spacing (R₁), 25-cm conventional row spacing (R₂), and 35-cm row spacing (R₃). The two-year investigations revealed that increased row spacing exhibited a significantly higher light transmission ratio (LT), which improved light conditions within the canopy; however, excessive light leakage losses in R₂ and R₃ treatments were not favorable to improved irradiation energy utilization efficiency. Aboveground biomass accumulation was influenced by row spacing. Two spike-type wheat accumulated greater biomass under 15-cm row spacing compared to other row spacing treatments, although a markedly improved photosynthetic rate (P_N), effective quantum yield of photosystem II (Φ_PSII) and maximal efficiency of photosystem II photochemistry (F_v/F_m) in the penultimate and third leaves were observed in R₂ and R₃ treatments. At the same time, a longer duration of CAP and green leaf area was maintained in R₁ during grain filling. Compared with conventional row spacing, Wennong6 in R₁ treatment obtained 21.0% and 19.1% higher grain yield in 2011 and 2012, respectively, while for Jimai22 it increased by 11.3% and 11.4%, respectively. A close association of yield with CAP and LAI at mid-grain filling was observed. In conclusion, for the tested growing conditions, decreasing the row spacing to an optimal distance (15 cm) maintained a longer duration of LAI and CAP during grain filling, made a better coordination of group and individual leaf photosynthesis, and accumulated higher aboveground biomass, leading to a greater grain yield. In addition, Wennong6 had a more rational canopy architecture than Jimai22 (improved LT and higher LAI) and CAP under 15-cm row spacing, leading to a higher grain yield, which indicated that the large-spike type cultivar has the potential to obtain higher yields by increasing plant density through optimum row spacing allocation (15 cm).     

应用高精度pH计测定植物的光合速率和呼吸速率

为方便、准确地测定植物的光合速率和呼吸速率,将高精度pH计和高灵敏复合电极引入测定系统.结合样品的测定,阐明了pH计法的测定原理、气路连接和复合电极的标定,并指出了测定过程中应注意的事项.     

Selenium Alleviate Cadmium Toxicity by Improving Nutrient Uptake,Antioxidative and Photosynthetic Responses of Garlic

Russian Journal of Plant Physiology - Selenium (Se) as a beneficial element in plant growth is able to reduce the adverse effects of abiotic stresses. However, the little attention has been paid to...     

Changes in Morphology,Anatomy, and Photosynthetic Capacity of Needles of Japanese Larch (Larix kaempferi) Seedlings Grown in High CO2 Concentrations

Photosynthetic traits of two-year-old Japanese larch seedlings (Larix kaempferi Carr.) grown at elevated CO₂ concentrations were studied in relation to structural changes in the needles. Seedlings were grown at two CO₂ concentrations, 360 (AC) and 720 (EC) mol mol^–1 at high and low nutrient supply rates, high N (HN) and low N (LN). The photosynthetic capacity fell significantly in EC+LN, but increased significantly in EC+HN. Since the mesophyll surface area exposed to intercellular space per unit leaf area (A^mes/A) is correlated with the photosynthetic rate, we measured A^mes/A for larch needles growing in EC. Changes of A^mes/A in both EC+HN and EC+LN were very similar to the changes in photosynthetic capacity. This suggests that the changes of A^mes/A in EC probably caused the changes in the photosynthetic capacity. The changes of A^mes/A in EC were attributed to changes in the mesophyll cell size and mesophyll cell number. The photosynthetic capacity in EC can be explained by taking morphological and structural adaptations into account as well as biochemical factors.     

Enhancing Drought Tolerance in Wheat through Improving MorphoPhysiological and Antioxidants Activities of Plants by the Supplementation of Foliar Silicon

The main objective of the research is to assess the role of foliar application of silicon (Si) for enhancing the survival ability of wheat under drought stress through improving its morphology, physicochemical and antioxidants activities. Treatments were five doses of Si at the rate of 2, 4, 6 and 8 mM and a control. After completion of seeds germination, pots were divided into four distinct groups at various field capacity (FC) levels, such as 100% FC (well-irrigated condition), 75% FC (slight water deficit), 50% FC (modest water deficit) and 25% FC (severe water deficit stress condition). Foliar application of Si at the rate of 2, 4, 6 and 8 mM and a control were given after 30 days of sowing at the tillering stage of wheat. Findings of the present investigation indicated that increasing the level of water deficit stress reduced the morphological parameters (such as root and shoot fresh and dry-biomass weight) and physico-biochemical events ((such as chlorophyll contents by estimating SPAD value), total free amino acid (TFAA), total soluble sugar (TSS), total soluble protein (TSP), total proline (TP), CAT (catalase), POD (peroxidase), SOD (superoxide dismutase) and APX (ascorbate peroxidase)) of wheat; while foliar application of Si at 6 mM at tillering stage enhanced the drought tolerance in wheat by increasing morphology and physiochemical characters under all levels of drought stress. Similarly, antioxidants activities in wheat also enhanced by the application of Si at 6 mM under normal as well as all drought stress levels. Therefore, it may be concluded that foliar application of Si at 6 mM at the tillering stage of wheat is an important indication for increasing the drought tolerance by improving the morphology, physico-biochemical and antioxidants activities in plants under deficit water (drought) conditions.     

Expression of Flowering Repressor Gene CsSVP,Carbohydrates, and Antioxidants Affected by Plant Growth Regulators in Saffron

Improving flower yield through lengthening flowering duration is a primary breeding objective in saffron (Crocus sativus L.). Asexual reproduction in saffron limits biodiversity and conventional breeding. Hence, eliciting flowering-related gene expression by plant growth regulators is one way to achieve this aim. The phytohormones methyl jasmonate (MeJA) and 6-benzyl amino purine (BAP) signals are received by the MADs-box gene family. In this study, to elucidate the role of phytohormones on flower development, plant were treated with BAP (0 and 5 mg L^?1), and methyl jasmonate (MeJA) (0, 20, and 100 mM) at three developmental stages of the saffron life cycle. Then, the expression of the SHORT VEGETATIVE PHASE (CsSVP) gene as a MADS-box gene family was assessed in the saffron corm. The activities of antioxidant enzymes, soluble sugar, starch content, and soluble protein content were also measured in corm, leaf, and root tissues. The application of MeJA and BAP treatments resulted in down-regulation of CsSVP expression in the corm during dormancy. At the dormancy stage, catalase, peroxidase activity decreased, and ascorbate peroxidase activity increased following MeJA treatment. In contrast, an increment in catalase and peroxidase activity and reduction of ascorbate peroxidase activity were observed after treatment with MeJA during the flowering stage. This change in enzyme activity is most likely due to flowering, which demands the re-allocation of resources. As flowering is a process heavily influenced by the environment, plants treated with MeJA, which may mimic environmental stress, showed changes in antioxidant enzyme activity. Overall, these results suggested that MeJA and BAP treatments play a significant role in the vegetative-to-reproductive phase change in saffron.

     

Overexpression of KiSS1 Induces the Proliferation of Hepatocarcinoma and Increases Metastatic Potential by Increasing Migratory Ability and Angiogenic Capacity

Liver cancer has a high prevalence, with majority of the cases presenting as hepatocellular carcinoma (HCC). The prognosis of metastatic HCC has hardly improved over the past decade, highlighting the necessity for liver cancer research. Studies have reported the ability of the KiSS1 gene to inhibit the growth or metastasis of liver cancer, but contradictory research results are also emerging. We, therefore, sought to investigate the effects of KiSS1 on growth and migration in human HCC cells. HepG2 human HCC cells were infected with lentivirus particles containing KiSS1. The overexpression of KiSS1 resulted in an increased proliferation rate of HCC cells. Quantitative polymerase chain reaction and immunoblotting revealed increased Akt activity, and downregulation of the G1/S phase cell cycle inhibitors. A significant increase in tumor spheroid formation with upregulation of β-catenin and CD133 was also observed. KiSS1 overexpression promoted the migratory, invasive ability, and metastatic capacity of the hepatocarcinoma cell line, and these effects were associated with changes in the expressions of epithelial mesenchymal transition (EMT)-related genes such as E-cadherin, N-cadherin, and slug. KiSS1 overexpression also resulted in dramatically increased tumor growth in the xenograft mouse model, and upregulation of proliferating cell nuclear antigen (PCNA) and Ki-67 in the HCC tumors. Furthermore, KiSS1 increased the angiogenic capacity by upregulation of the vascular endothelial growth factor A (VEGF-A) and CD31. Based on these observations, we infer that KiSS1 not only induces HCC proliferation, but also increases the metastatic potential by increasing the migratory ability and angiogenic capacity.     

甜菜碱提高植物抗寒性的机理及其应用

甜菜碱是植物重要的渗透调节物质,在低温等逆境条件下,许多植物细胞中迅速积累甜菜碱以维持细胞的渗透平衡.对近几年来甜菜碱提高植物抗寒性的机理研究及其应用,包括甜菜碱的生物合成途径、低温胁迫下甜菜碱对植物的保护机理、甜菜碱合成酶基因的转化及外源甜菜碱在植物抗寒中的应用进行了综述.     

Heat Changes in Maize Storage Influenced by Compound Factors; Different Levels of Maize Weevils,Broken Corn and Foreign Materials,and Moisture Contents

Effect of Sitophilus zeamais Mostschulsky infestation on the heat changes of maize at 13, 16, and 19% moisture content with 0, 5, and 10% broken corn and foreign material was studied in 1.81 thermos containers. Containers with infested and uninfested maize were held in a chamber at 26.6°C and 60±5% r.h. for 80 d. Temperatures were measured continuously using a datalogger system. At 13 and 16% moisture content, more grain heating was recorded in infested than in uninfested maize. Presence of insects and moisture content level were major factors in grain heating during storage. Level of BCFM did not significantly affect the grain heating. At 19% moisture content, grain heating increased in all treatments. Heating appeared to be more related to microbial growth than to insect activity, and accumulated to 26.5–37 kj/kg maize at 3–4 wk. The growth of the maize weevil population was significantly affected by grain moisture content. The greatest number of offspring after 80 d was recorded in the 13% moisture content trial. At 19% moisture content, there were more dead than live insects.     

Photoprotection Conferred by Changes in Photosynthetic Protein Levels and Organization during Dehydration of a Homoiochlorophyllous Resurrection Plant

During desiccation, homoiochlorophyllous resurrection plants retain most of their photosynthetic apparatus, allowing them to resume photosynthetic activity quickly upon water availability. These plants rely on various mechanisms to prevent the formation of reactive oxygen species and/or protect their tissues from the damage they inflict. In this work, we addressed the issue of how homoiochlorophyllous resurrection plants deal with the problem of excessive excitation/electron pressures during dehydration using Craterostigma pumilum as a model plant. To investigate the alterations in the supramolecular organization of photosynthetic protein complexes, we examined cryoimmobilized, freeze-fractured leaf tissues using (cryo)scanning electron microscopy. These examinations revealed rearrangements of photosystem II (PSII) complexes, including a lowered density during moderate dehydration, consistent with a lower level of PSII proteins, as shown by biochemical analyses. The latter also showed a considerable decrease in the level of cytochrome f early during dehydration, suggesting that initial regulation of the inhibition of electron transport is achieved via the cytochrome b₆f complex. Upon further dehydration, PSII complexes are observed to arrange into rows and semicrystalline arrays, which correlates with the significant accumulation of sucrose and the appearance of inverted hexagonal lipid phases within the membranes. As opposed to PSII and cytochrome f, the light-harvesting antenna complexes of PSII remain stable throughout the course of dehydration. Altogether, these results, along with photosynthetic activity measurements, suggest that the protection of retained photosynthetic components is achieved, at least in part, via the structural rearrangements of PSII and (likely) light-harvesting antenna complexes into a photochemically quenched state.Desiccation tolerance, the ability to survive absolute water contents down to approximately 0.1 g water g⁻¹ dry weight, is a trait found in some bacteria, algae, fungi, as well as animals and plants. In the plant kingdom, desiccation tolerance is common in ferns, mosses, and most seeds and pollen of flowering plants (angiosperms). Resurrection plants, a diverse group of approximately 300 angiosperm species, possess this trait also in their vegetative tissues. These plants are able to withstand prolonged periods of dehydration and to recover within hours to a few days once water is available. A major and interesting aspect in the study of desiccation tolerance in resurrection plants is how they protect themselves against oxidative damage during dehydration, which is often accompanied by conditions of high irradiance (for review, see Bartels and Hussain, 2011; Farrant and Moore, 2011; Morse et al., 2011).A decrease in water content quickly results in lowered leaf stomatal conductance and, consequently, decreased uptake of CO₂. This hinders and ultimately blocks the Calvin cycle. The light-driven reactions, however, typically continue well after the onset of water deficiency, with intact chlorophyll-protein complexes absorbing light energy. The imbalance between the light reactions and the downward biochemical pathways results in a lack of electron sinks and in the system becoming overenergized. This, in turn, leads to enhanced generation of reactive oxygen species (ROS), which inflict damage onto photosynthetic components as well as onto other chloroplast and cellular constituents. At times, the damage may be severe and lead to irreversible impairment and finally plant death (Dinakar et al., 2012).Resurrection plants minimize such potential ROS damage by shutting down photosynthesis during early stages of dehydration (Farrant, 2000; Farrant et al., 2007). There are two mechanisms whereby this is achieved. In poikilochlorophyllous resurrection plants, chlorophyll, along with photosynthetic protein complexes, are degraded, and thylakoids, the membranes that host the photosynthetic pigment-protein complexes, are dismantled. This straightforward mechanism prevents the formation of ROS, yet it comes at the cost of resynthesizing photosynthetic components de novo upon rehydration. On the other hand, homoiochlorophyllous species retain most of their photosynthetic complement and so must rely on other means to protect themselves from oxidative damage in the desiccated state. Some of these, such as leaf folding or curling, which minimize the exposure of inner leaves and/or of adaxial (upper) leaf surfaces to the light, and the accumulation of anthocyanins in leaf surfaces, which act as sunscreens, and the presence of reflective hairs and waxy cuticles, reduce the overall absorption of radiation and thus protect against photodamage (Sherwin and Farrant, 1998; Farrant, 2000; Bartels and Hussain, 2011; Morse et al., 2011). ROS that are generated are dealt with by antioxidants, ROS scavengers, and in some cases also by anthocyanins and other polyphenols (Moore et al., 2005; Kytridis and Manetas, 2006; Farrant et al., 2007). Nevertheless, all of these mechanisms are insufficient to completely prevent and/or detoxify all ROS that are formed, necessitating additional means to prevent or deal with possible damage that ROS may inflict during dehydration and while desiccated (Dinakar et al., 2012).The major photoprotective mechanism in plants and algae is nonphotochemical quenching (NPQ), in which excess light energy absorbed at the antennae of PSII is dissipated as heat. NPQ has been shown to be active in desiccation-tolerant bryophytes and pteridiophytes (Eickmeier et al., 1993; Oliver, 1996), in homoiochlorophyllous angiosperms (Alamillo and Bartels, 2001; Georgieva et al., 2009; Dinakar and Bartels, 2012; Huang et al., 2012), and during the initial stages of drying in poikilochlorophyllous angiosperms (Beckett et al., 2012). Photoinhibition, when damage to PSII (mainly to its D1 subunit) exceeds the repair capacity, typically under conditions of light stress, is also observed in homoiochlorophyllous resurrection plants (e.g. Georgieva and Maslenkova, 2006). Other ways to avoid ROS-induced damage include the rerouting of reducing equivalents to alternative electron sinks, such as the water-water cycle and/or photorespiration, as well as structural rearrangements of PSII and light-harvesting antenna (LHCII) complexes into energy-dissipating states (for review, see Dekker and Boekema, 2005; Yamamoto et al., 2014). These latter processes, in particular the ones pertaining to possible changes in PSII-LHCII macrostructure, have not yet been characterized in homoiochlorophyllous resurrection plants.To gain insight into the ways homoiochlorophyllous resurrection plants cope with dehydration while retaining most of their photosynthetic apparatus, we combined microscopic, spectroscopic, and biochemical approaches. Investigation of the supramolecular organization of photosynthetic complexes was carried out using cryoscanning electron microscopy (cryo-SEM) of high-pressure frozen, freeze-fractured leaf samples; to our knowledge, this combination of procedures has not been utilized previously to investigate thylakoid membranes within plant tissues.The studies reveal that during dehydration, the density of PSII in grana membranes gradually decreases. Notably, in the dehydrated state, in which photosynthetic activity is halted, PSII complexes are also observed to be arranged into rows and two-dimensional arrays. These arrangements are proposed to represent quenched PSII complexes that likely minimize the generation of ROS during desiccation. Furthermore, we observe inverted hexagonal (H_II) phases in this dry state, and these two structural rearrangements are correlated with the massive accumulation of Suc. Biochemical studies of thylakoid membrane fractions support the finding that the relative level of PSII proteins decreases during dehydration. These analyses also reveal that the level of the cytochrome f subunit of the cytochrome b₆f complex decreases quite dramatically and early during dehydration. This provides evidence for an additional level of regulation that inhibits/shuts down the photosynthetic light reactions during desiccation.