Aspects of adaptive answering formation in virus-host plant pathosystem for different wheat cultivars under simulating microgravity condition

Investigations of prolonged clinorotation effect on some morphological and physiological parameters under Wheat streak mosaic virus WSMW-infection of Apogee and Lada wheat cultivars were carried out. Experiments were held on universal clinostat CYCLE-2. Clinorotation caused changing of WSMV virions shape and reducing of the virus reproduction. Apogee wheat plants grown under two stress factors (infection and clinorotation) produced more kernels than stationary (motionless) plants, but the average weight of kernel was lower. Under clinorotation changes in host plant-virus system take place and adaptive reactions for simulated microgravity conditions form. These lead to reduction of potyvirus replication.     

Clinorotation affects soybean seedling morphology

Although spaceflight does not appear to significantly affect seed germination, it can influence subsequent plant growth. On STS-3 and SL-2, decreased growth (measured as plant length, fresh weight and dry weight) was noted for pine, oat and mung bean. In the CHROMEX-01 and -02 experiments with Haplopappus and in the CHROMEX-03 experiment with Arabidopsis, enhanced root growth was noted in the space-grown plants. In the CHROMEX-04 experiment with wheat, both leaf fresh weight and leaf area were diminished in the space-grown plants but there was no difference in total plant height (CS Brown, HG Levine, and AD Krikorian, unpublished data). These data suggest that microgravity impacts growth by whole plant partitioning of assimilates. The objective of the present study was to determine the influence of clinorotation on the growth and morphology of soybean seedlings grown in the BRIC (Biological Research In Canister) flight hardware. This experiment provided baseline data for a spaceflight experiment (BRIC-03) flown on STS-63 (Feb. 3-11, 1995).     

Photosynthate Partitioning into Starch in Soybean Leaves: I. Effects of Photoperiod versus Photosynthetic Period Duration

Photosynthesis, photosynthate partitioning into foliar starch, and translocation were investigated in soybean plants (Glycine max (L.) Merr. cv. Amsoy 71), grown under different photoperiods and photosynthetic periods to determine the controls of leaf starch accumulation. Starch accumulation rates in soybean leaves were inversely related to the length of the daily photosynthetic period under which the plants were grown. Photosynthetic period and not photoperiod per se appears to be the important factor. Plants grown in a 14-hour photosynthetic period partitioned approximately 60% of the daily foliar accumulation into starch whereas 7-hour plants partitioned about 90% of their daily foliar accumulation into starch. The difference in starch accumulation resulted from a change in photosynthate partitioning between starch and leaf residual dry weight. Residual dry weight is defined as leaf dry weight minus the weight of total nonstructural carbohydrates. Differences in photosynthate partitioning into starch were also associated with changes in photosynthetic and translocation rates, as well as with leaf and whole plant morphology. It is concluded that leaf starch accumulation is a programmed process and not simply the result of a limitation in translocation.     

Ontogeny of Daucus carota Infected with Meloidogyne hapla

The ontogeny of carrots (Daucus carota cv. ''Spartan Premium'') grown under greenhouse conditions in pots of organic soil infected with Meloidogyne hapla was influenced detrimentally as early as 4 days after seeding, as determined through analysis of plant surface area, dry weight, fresh weight, net assimilation rate, relative growth rate, and leaf-area ratio. Only 58% of the diseased carrots were suitable for fresh market, compared with 97% of those grown in nematode-free soil. Growth and development of the shoot system (height, surface area, dry weight, and fresh weight) were retarded by M. hapla as early as 12 days after seeding. During the first 12 days after seeding, root dry weight was greater for diseased plants than for controls. Root growth and development (surface area, dry weight, and fresh weight) associated with this nematode, however, were retarded as early as 16 days after seeding. M. hapla caused a delay in the occurrence of 2nd-, 4th-, and 5th-order roots, and an increase in the occurrence of 6th-order roots in infected plants. Parasitized plants had 44% fewer roots (primary through 6th-order) and 50% less total root length.     

Growth,yield and reproduction of dwarf tomato grown under simulated microgravity conditions

Abstract

A closed hydroponic system combined with a horizontal uniaxial clinostat has been used to grow tomato plants (Solanum lycopersicum L.) under simulated microgravity conditions. The study was carried out to evaluate the quanti-qualitative traits (growth, yield and quality) of the dwarf tomato variety ‘Micro-Tom’ grown under simulated microgravity conditions and to determine if tomato plants would complete their life cycle (‘seed-to-seed’). Morphological and growth characteristics of ‘Micro-Tom’ were modified during clinorotation treatment. The ‘Micro-Tom’ plants grown under simulated microgravity exhibited a spreading growth and an increasing of the internode length. Total fruit yield, small fruit yield, leaf area, leaf dry weight, fruit dry weight, total dry weight and shoot – root ratio were lower in the clinorotated tomato plants than those grown in the control treatment. Foliar amount of carotenoids, and chlorophyll a and b were also substantially reduced under simulated microgravity conditions. Quality parameters (total soluble solids and fruit dry matter) of tomato plants were also negatively affected by clinorotation. The number of flowers per plant was increased by 32% in clinorotated plants versus controls. Fruit setting was reduced by 46% under clinorotation, while no significant difference was recorded for the pollen fertility and the seed number in small and large fruits. Clinorotation-exposed and control seeds were used in a germination trial in order to evaluate whether the seeds so formed were viable and if subsequent generations might be obtained in microgravity. Seeds formed under simulated microgravity proved to be biologically and functionally complete (germination = 78.6%) showing that ‘Micro-Tom’ plants could realize complete ontogenesis, from seed to seed in microgravity.     

Fatty acid content and the functional state of pea chloroplasts under altered gravity

The results of the study of the fatty acid content and the functional state of chloroplasts isolated from leaves of pea plants grown during 7 and 14 days in the stationary conditions and under clinorotation (2 rpm) are presented. An increase in the unsaturated fatty acid content occurred after 7-day clinorotation while it insignificantly decreased after more prolonged 14-day clinorotation. A study of the functional state of chloroplasts (the rate of electron transport in photosystems II [PSII] and in photosystem I [PSI] and in the whole photosynthetic electron transport chain) showed its decrease under both terms of clinorotation in comparison with control ones. In addition, 14-day clinorotation caused more significant lowering of the electron transport rate, particularly in PSI. Changes in both the fatty acid content and the electron transport rate are discussed in relation to the activation of lipid peroxidation and the increased production of activated oxygen species in chloroplasts under clinorotation.     

Protein expression in Arabidopsis thaliana after chronic clinorotation

Soluble protein expression in Arabidopsis thaliana L. (Heynh.) leaf and stem tissue was examined after chronic clinorotation. Seeds of Arabidopsis were germinated and plants grown to maturity on horizontal or vertical slow-rotating clinostats (1 rpm) or in stationary vertical control units. Total soluble proteins and in vivo-labeled soluble proteins isolated from these plants were analyzed by two-dimensional SDS PAGE and subsequent fluorography. Visual and computer analysis of the resulting protein patterns showed no significant differences in either total protein expression or in active protein synthesis between horizontal clinorotation and vertical controls in the Arabidopsis leaf and stem tissue. These results show chronic clinorotation does not cause gross changes in protein expression in Arabidopsis.     

Inhibition of Polar Auxin Transport by Ethylene

Applied ethylene influences the growth of etiolated pea stem sections cut from untreated plants, but has no effect on (14)C-indoleacetic acid uptake, polar transport or destruction. However, the capacity of the polar auxin transport system is markedly reduced in sections cut from plants grown in ethylene, while the velocity of auxin transport is unchanged under these conditions. Inhibition of the polar transport system by ethylene could underlie certain responses in which the gas produces symptoms of auxin deficiency.     

Automorphosis of etiolated pea seedlings in space is simulated by a three-dimensional clinostat and the application of inhibitors of auxin polar transport

Etiolated pea (Pisum sativum L. cv. Alaska) seedlings grown under microgravity conditions in space show automorphosis: bending of epicotyls, inhibition of hook formation and changes in root growth direction. In order to determine the mechanisms of microgravity conditions that induce automorphosis, we used a three-dimensional clinostat and obtained the successful induction of automorphosis-like growth of etiolated pea seedlings. Kinetic studies revealed that epicotyls bent at their basal region towards the clockwise direction far from the cotyledons from the vertical line (0 degrees) at approximately 40 degrees in seedlings grown both at 1 g and in the clinostat within 48 h after watering. Thereafter, epicotyls retained this orientation during growth in the clinostat, whereas those at 1 g changed their growth direction against the gravity vector and exhibited a negative gravitropic response. On the other hand, the plumular hook that had already formed in the embryo axis tended to open continuously by growth at the inner basal portion of the elbow; thus, the plumular hook angle initially increased; this was followed by equal growth on the convex and concave sides at 1 g, resulting in normal hook formation; in contrast, hook formation was inhibited on the clinostat. The automorphosis-like growth and development of etiolated pea seedlings was induced by auxin polar transport inhibitors (9-hydroxyfluorene-9-carboxylic acid, N-(1-naphthyl)phthalamic acid and 2,3,5-triiodobenzoic acid), but not by anti-auxin (p-chlorophenoxyisobutyric acid) at 1 g. An ethylene biosynthesis inhibitor, 1-aminooxyacetic acid, inhibited hook formation at 1 g, and ethylene production of etiolated seedlings was suppressed on the clinostat. Clinorotation on the clinostat strongly reduced the activity of auxin polar transport of epicotyls in etiolated pea seedlings, similar to that observed in space experiments (Ueda J, Miyamoto K, Yuda T, Hoshino T, Fujii S, Mukai C, Kamigaichi S, Aizawa S, Yoshizaki I, Shimazu T, Fukui K (1999) Growth and development, and auxin polar transport in higher plants under microgravity conditions in space: BRIC-AUX on STS-95 space experiment. J Plant Res 112: 487492). These results suggest that clinorotation on a three-dimensional clinostat is a valuable tool for simulating microgravity conditions, and that automorphosis of etiolated pea seedlings is induced by the inhibition of auxin polar transport and ethylene biosynthesis.     

Maize root response to N in the greenhouse and field

Summary Root growth and morphology were compared between seven week old maize plants grown in the greenhouse and in the field. The plants were similar in shoot dry weight and the partioning of N and dry matter to roots were similar except for the field grown plants in 1983. Field grown plants had greater root mass per length and greater calculated diameter than greenhouse plants. Nitrogen fertilization decreased N and dry matter partitioning to the root system in all three environments.     

Effect of spaceflight on isoflavonoid accumulation in etiolated soybean seedlings

In order to explore the potential impact of microgravity on flavonoid biosynthesis, we examined isoflavonoid levels in soybean (Glycine max) tissues generated under both spaceflight and clinorotation conditions. A 6-day Space Shuttle-based microgravity exposure resulted in enhanced accumulation of isoflavone glycosides (daidzin, 6"-O-malonyl-7-O-glucosyl daidzein, genistin, 6"-O-malonyl-7-O-glucosyl genistein) in hypocotyl and root tissues, but reduced levels in cotyledons (relative to 1g controls on Earth). Soybean seedlings grown on a horizontally rotating clinostat for 3, 4 and 5 days exhibited (relative to a vertical clinorotation control) an isoflavonoid accumulation pattern similar to the space-grown tissues. Elevated isoflavonoid levels attributable to the clinorotation treatment were transient, with the greatest increase observed in the three-day-treated tissues and smaller increases in the four- and five-day-treated tissues. Differences between stresses presented by spaceflight and clinorotation and the resulting biochemical adaptations are discussed, as is whether the increase in isoflavonoid concentrations were due to differential rates of development under the "gravity" treatments employed. Results suggest that spaceflight exposure does not impair isoflavonoid accumulation in developing soybean tissues and that isoflavonoids respond positively to microgravity as a biochemical strategy of adaptation.     

Structural and functional organization of mitochondria in soybean root statocytes under microgravitation

The effects of microgravity and ethylene on morphology and ultrastructural organization of mitochondria in root statocytes of soybean seedlings grown for 6 days on the board of the space shuttle Columbia during the STS-87 mission were investigated. The spaceflight seedlings and the ground-grown control seedlings were grown in BRIG (Biological Research in Canister) in the presence of KMnO4 to remove ethylene. It was revealed that irrespectively of KMnO4 treatment the mitochondria in the spaceflight seedlings were characterized by round or oviform and by low electron density of organelle matrix, whereas the organelles in the ground controls were polymorphic in shape and had higher electron density of matrix. The possible mechanisms of morphological and ultrastructural rearrangements of mitochondria that may be involved in adaptation processes of soybean seedlings to microgravity conditions are discussed.     

Modification by ethylene of the cell growth pattern in different tissues of etiolated lupine hypocotyls

The influence of ethylene on growth in etiolated lupine (Lupinus albus L.) hypocotyls was studied in ethephon-treated plants. Ethephon reduced the length and increased the diameter of hypocotyls. At the end of the hypocotyl growth period (14 days), the fresh weight was reduced by 53%, and the dry weight was reduced by 16%. Thus, ethylene reduced water uptake in the tissues to a greater extent than the incorporation of new materials. Light microscopic measurements showed that the thickness of tissues was stimulated by ethylene, the vascular cylinder and cortex exhibiting greater increases (55 and 45%, respectively) than pith (26%) or epidermis (12%). Ethephon modified the cell growth pattern, stimulating lateral cell expansion and cell wall thickness, while reducing cell elongation. The response to ethylene varied in the different tissues and was higher in cortex and pith cells than in the epidermis cells. The ethylene-induced cell expansion in the cortex varied according to the localization of cells in the tissue: the central and subepidermal layers showed little change, whereas the innermost layers exhibited the greatest increase. Electron microscopy revealed that ethylene increased both the rough endoplasmic reticulum and dictyosomes, suggesting that ethylene stimulated the secretion of cell wall materials. In untreated seedlings, the pattern of cell growth was similar in cells from the epidermis, cortex, and pith. The final cell size varied along the hypocotyl, the cells becoming shorter and broader the closer to the basal zones of the organ.     

Effects of ethylene on somatic embryogenesis and galanthamine content in <Emphasis Type="Italic">Leucojum aestivum</Emphasis> L. cultures

The influence of ethylene on in vitro morphogenesis of Leucojum aestivum and galanthamine accumulation was studied. Calli were cultivated on Murashige and Skoog (MS) medium supplemented with 25 μM 4-amino-3,5,6-trichloropicolinic acid (picloram) and 0.5 μM benzyladenine (BA). During incubation under these conditions, callus cultures produced ethylene (9.5 nL/g fresh weight: F.W.) whereas no ethylene was found in somatic embryos cultivated on medium supplemented with 0.5 μM α-naphthalene acetic acid (NAA) and 5 μM zeatin. Application of the precursor of ethylene 1-aminocyclopropane-1-carboxylic acid (ACC) increased ethylene production in both cultures, and decreased callus growth by a factor of 1.2, whereas callus growth was enhanced by a factor of 1.1 in the presence of an inhibitor of ethylene silver nitrate (AgNO₃) or by a factor of 1.2 with an absorbent potassium permanganate (KMnO₄). ACC enhanced the induction of somatic embryos and the development of globular embryos. Removal of ethylene by KMnO₄ during somatic embryogenesis led to the development of plants with greater length. Silver thiosulphate (STS) induced galanthamine production in callus cultures (0.1% dry weight), whereas ACC induced galanthamine production in somatic embryo cultures (2% dry weight).     

Ultrastructure of statocytes and cells of distal elongation zone of Arabidopsis thaliana under clinorotation

Results of the electron-microscopic investigation of root apices of Arabidopsis thaliana 3-, 5- and 7-days-old seedlings grown in the stationary conditions and under clinorotation are presented. It was shown the similarity in the root apex cell ultrastructure in control and under clinorotation. At the same time there were some differences in the ultrastructure of statocytes and the distal elongation zone under clinorotation. For the first time the sensitivity of ER-bodies, which are derivatives of GER and contain beta-glucosidase, to the influence of simulated microgravity was demonstrated by increased quantity and area of ER-bodies at the cell section as well as by higher variability of their form under clinorotation. A degree of these changes correlated with the duration of clinorotation. On the basis of experimental data a protective role of ER-bodies in adaptation of plants to microgravity is supposed.     

Influence of cadmium and nickel on growth,net photosynthesis and carbohydrate distribution in rice plants

Six day old rice seedlings (Oryza sativa L. cv. Bahía) were grown for 5 or 10 days in a nutrient solution with either Cd (0.01, 0.1 mmol/l) or Ni (0.1, 0.5 mmol/l). Both Cd and Ni reduced the length of shoots and roots depending on the concentration and type of ion tested. On the other hand, the dry weight to fresh weight ratio was increased by heavy metal treatments, especially in the aerial part of 0.5 mmol/l Ni treated plants. The application of 0.1 mmol/l Cd and 0.5 mmol/l Ni to the seedlings produced an inhibition of the transport of carbohydrate reserves from the seeds from which plants were developing, to the rest of the plant. Net photosynthesis was also inhibited in treated plants. However, the total carbohydrate content in the shoots of these plants was higher than in controls. Thus, the starch, soluble sugars and sucrose content in the shoots of 0.5 mmol/l Ni treated plants was respectively up to 2.6, 2.8 and 4 times greater compared to controls. The distribution of assimilates between organs was also affected by the treatment: the carbohydrate content increased in the stem and second leaf but it was not affected or decreased in the root and third leaf. Although less evident, the effect of Cd on carbohydrate distribution and content was similar to that of Ni. The possible mechanisms involved in the abnormal carbohydrate accumulation and distribution are discussed.Abbreviations 0 DT plants at day zero of treatment - 5 DT five days treated plants - 10 DT ten days treated plants - DW dry weight - FW fresh weight     

The influence of the origin of the mother plant on yield and germination of their caryopses in Aegilops ovata

Summary Dispersal units of Aegilops ovata contain in their spikelets caryopses differing in morphology, weight and germinability according to their position in the spikelets. Plants originating from caryopses of the diverse orders were grown under various photo- and thermoperiodic conditions, and the caryopses harvested germinated under uniform conditions. Under all conditions tested, the relative difference in weight between the caryopses of the various orders was not affected. But plants grown under long days and/or low temperatures produced heavier caryopses than plants grown under short days and/or high temperatures respectively. There was a positive correlation between weight and germinability in caryopses of the various orders derived from one mother plant, and a reverse correlation in caryopses formed on mother plants grown under low and high temperatures. When mother plants arising from various orders of caryopses were grown under long days and low temperatures, they produced caryopses of different germinability, showing that the origin of the mother plant may affect the germination qualities of its offspring. The implications of these results are discussed.     

The effect of shading on photosynthesis,growth, and regrowth following defoliation for Bromus tectorum

Summary The effect of full sunlight, 60%, or 90% attenuated light on photosynthetic rate, growth, leaf morphology, dry weight allocation patterns, phenology, and tolerance to clipping was examined in the glasshouse for steppe populations of the introduced grass, Bromus tectorum. The net photosynthetic response to light for plants grown in shade was comparable to responses for plants grown in full sunlight. Plants grown in full sunlight produced more biomass, tillers and leaves, and allocated a larger proportion of their total production to roots than plants grown in shade. The accumulation of root and shoot biomass over the first two months of seedling growth was primarily responsible for the larger size at harvest of plants grown in full sunlight. Plants grown under 60% and 90% shade flowered an average of 2 and 6 weeks later, respectively, than plants grown in full sunlight. Regrowth after clipping was greater for plants grown in full sunlight compared to those grown in shade. Even a one-time clipping delayed flowering and seed maturation; the older the individual when leaf area was removed, the greater the delay in its phenology. Repeated removal of leaf area was more frequently fatal for plants in shade than in full sunlight. For plants originally grown in full sunlight, regrowth in the dark was greater than for shaded plants and was more closely correlated to non-flowering tiller number than to plant size. This correlation suggests that etiolated regrowth is more likely regulated by the number of functional meristems than by differences in the size of carbohydrate pools. Thus, shading reduces the rate of growth, number of tillers, and ability to replace leaf area lost to herbivory for B. tectorum. These responses, in turn, intensify the effect of competition and defoliation for this grass in forests. B. tectorum is largely restricted to forest gaps at least in part because of its inability to acclimate photosynthetically, the influence of shade on resource allocation, and the role of herbivory in exacerbating these effects.     

Expression of the narrow leaflet gene for yield and agronomic traits in soybean

Genes that affect plant form and function may be used to enhance the yield of soybean [Glycine max (L.) Merr.]. Most soybean cultivars have broad (ovate) leaflets. A single gene, ln, controls inheritance for the narrow leaflet characteristic. Narrow leaflet cultivars (ln/ln) also tend to have a higher percentage of four-seeded pods than ovate (Ln/Ln) leaflet cultivars. Heterozygous (Ln/ln) plants have a leaflet shape intermediate between narrow and ovate. Determining the agronomic effects of the narrow leaflet allele (ln) in the heterozygous (Ln/ln) condition in soybean may have applications in practical plant breeding. We studied an ovate leaflet and a narrow leaflet cultivar, crosses between them in the F(1) and F(2), and backcrosses to both cultivars. The ratio of leaflet width to leaflet length accurately distinguished among narrow, ovate, and intermediate leaflet plants in the F(2) and backcross generations. In the F(2) generation, differences occurred among plants with different leaflet morphology. Narrow leaflet plants produced more seeds per pod and lower seed weight than ovate leaflet plants. Narrow and ovate leaflet plants produced comparable numbers of pods per plant and plant yield. Compared to ovate leaflet plants, intermediate leaflet plants produced similar numbers of seeds per pod and seed weight. Intermediate leaflet plants produced significantly more pods per plant and plant yield than plants with either ovate or narrow leaflets. The heterozygous condition at the locus for leaflet morphology resulted in heterosis for plant yield and may be of benefit in association with commercialization and development of hybrid soybean.     

Water-Stress-Induced Ethylene Production in Wheat : A Fact or Artifact?

Effects of water stress on ethylene evolution from excised leaf segments and intact plants of wheat (Triticum aestivum L. cv Katepwa) were studied. Excised leaf segments of 8 day or 6 week old plants were dried until they lost 8% of their fresh weight (water potential about −2.3 megapascals). These and nondried control leaf segments (water potential about −1.0 megapascal) were sealed in glass tubes, and their ethylene production rates were compared by head space analysis via gas-chromatography. The dried leaves of both ages produced significantly more ethylene than the corresponding controls. However, when 6 week old intact plants were water-stressed by withholding water supply, and their ethylene production measured using a continuousflow system, no increase in ethylene was deteceted despite a drop in water potential to −2.9 megapascals over 6 days. Even the leaf segments excised from plants that had been subjected to water stress for 2, 4, or 6 days produced no more ethylene (in sealed tubes) than the leaves from well-watered plants. In fact, the ethylene production by these segments decreased with the increase in the severity of stress experienced by the plants. The results show that the commonly reported overproduction of ethylene by excised leaves subjected to rapid drying represents an artifact, which has little relevance to the water stress responses of intact wheat plants.