摘要:

We have examined the graviresponding sites in the shoots of seedlings of rice (OryzasativaL.) and their relation to the agravitropic growth of a‘lazy’line. The graviresponding sites of the seedling shoots of a japonica type of rice. cv. Kamenoo. shifted from the mesocotyl/coleoplile region to the leaf‐shealh base when the shoots grew in the dark. A lazy line ot rice. lazy‐Kamenoo. showed gravicurvature in the mesocotyl/ coleoptile region at the early stage of growth, hut eventually lost its graviresponse as the seedlings grew. The loss of graviresponsiveness of lazy‐Kamenoo was attributed to a reduced response of the coleoptile and a diminished response of the leal‐sheath base to gravity. Later. the leaf‐sheath base of lazy‐Kamenoo became gravitropically incompetent. causing agravitropic growth of the shoots. Thus, shoots of lazy‐Kamenoo lose graviresponsiveness in an organ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08823.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In an attempt to manipulate plant nitrogen‐sink strength, various defoliation treatments were applied to white clover (Trifolium repentL. cv. Ladino) grown in a controlled environment. Nitrogenase activity and its oxygen limitation were measured as H;evolution in Ar:O2using a flow‐through gas exchange system. An experiment to monitor the response of nitrogenase activity to various degrees of defoliation showed that the removal of up to 50% of the leaf are a had no effect on nitrogenase activity within 6 h. If more than 50% of the leaf area was removed. the nitrogenase activity decreased in relation to the loss of leaf area. This was accompanied by a corresponding increase in the O2limitation of nitrogenase activity. In the experiment to determine the N‐sink strength after defoliation, the dry weight increase w as initially unaffected by the removal of 4% of the leaf area, whereas removal of 85% or 100% of the leaf area resulted in a dry weight loss for several days. The time course of nitrogen assimilation was similar to that of dry weight increase. This study provides substantial evidence that after a severe defoliation the nitrogen demand is temporarily restricted due to the lack of dry weight increase. Since the plant's ability to store organic nitrogen is very limited. it seems plausible that nitrogen assimilation in the still fully intact symbiotic system had to be down‐regulated. Consequently, to avoid ammonia toxicity. nitrogenase activity had to be reduced. Such an interpretation is supported by the fact that complete defoliation of nitrogen‐Starved plants caused a much milder decrease in nitrogenase activity compared to the decrease in plants well supplied with nitrogen. The present data are consistent with the hypothesis that after defoliation nitrogenase activity is adjusted in response to the reduced demand for symbiotically fixed nitrogen (nitrogen‐sink strength), It is proposed that such an adjustment could he made by a nitrogen feedback mechanism that regulates a variable oxygen‐diffusion barrier i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08824.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Effects of CO2enrichment on photosynthesis and on dry matter allocation were examined in two tobacco (Nicotiana tabaumL.) genotypes. Samsun and W38. Plants were grown from seed in controlled environment chambers at a photosynthetic photon flux density of 450 μmol m−2s−1. Averaged over the 9 day study, net photosynthesis rates were 14.2±0.5 and 13.0±0.4 μmol m−2s−1in elevated (70 Pa) and in ambient (35 Pal CO2air. respectively, when measured at the irradiance and CO2partial pressure employed for plant growth. However. photosynthesis rates of plants grown in elevated CO2were 50% less than those of the ambient controls on the last day of treatment, when measured al 70 Pa CO2air and an irradiance of 900 μmol m−2s−1Total plant dry weight and specific leaf weight were greater (P<0.051 in enriched‐CO2‐grown than in ambient‐CO2‐grown plants. Leaf starch, measured during the first hour of the photoperiod. increased over 7 days of treatment in elevaled‐CO2‐grown but not in ambient‐CO2‐grown plants. Ribulose 1.5‐bisphosphate carboxylase/oxygenase (Rubisco) activities of tobacco plants grown at 35 and 70 Pa CO2air were 58.5±4.5 and 48.5±3.7 umol m−2s−1. respectively, between days 0 and 9 of the study. Rubisco activation state. Rubisco protein concentration. soluble protein and total chlorophyll were unaffected by CO2enrichment. The above findings demonstrated that photosynthesis was down regulated in tobacco plants after 7 to 9 days of CO2enrichment at low photosynthetic photon flxu densit

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08825.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The plasma membrane H‐ATPase (EC 3.1.6.35) was solubilized from isolated spinach (Spinacia oleracea) leaf plasma membranes using the detergent dodecyl‐β‐d‐maltoside and subsequently purified to near homogeneity by ion exchange chromatography (FPLC). The enzyme purified in the presence of glycerol and ATP showed no loss in activity during 8 h on ice nor upon freezing at ‐80°C and thawing, and the recovery was up to 75%. Addition of a phospholipid mixture only marginally increased the activity, whereas addition of lysophosphalidylcholine (lyso‐PC) resulted in a 2‐fold increase in activity and a decrease in Kmlor ATP from ca 300 μMto 100 μM. The membrane‐bound and the purified H‐ATPases showed very similar properties, also in their responses to lyso‐PC. which is believed to activate the enzyme by displacement of its C‐terminal inhibitory domain. Taken together, the data indicate that the H‐ATPase is purified in a non‐activated form su

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08826.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Endogenous levels of ethylene appeared to he suhoptimal for somatic embryogenesis in a suspension culture of carrot. Low concentrations of 1‐aminocyclopropane‐1‐carboxylic acid (ACC). 2‐chloroethylphosphonic acid (ethephon) and elhylene stimulated embryogenesis whereas higher concentrations were inhibitory. The stimulation by ACC was through its conversion to ethylene. whereas the inhibition by ACC was not. Low concentrations of AgNO3. an inhibitor of ethylene action, inhibited embryo‐genesis but stimulated ethylene production. Aminoethoxyvinylglycine (AVG) and aminooxyacetic acid (AOA). commonly used inhibitors of ACC synthase. inhibited both embryogenesis and ethylene production. However, the inhibition of embryogenesis was not related to the inhibition ote ethylene production. Very low concentrations of AVG stimulated embryo production in a way unrelated to its effect on ethylene production. Salicylic acid and CoCl2. inhibitors of ACC oxidase in other systems, inhibited embryogenesis but. again, in way(s) unrelated to their inhibition of ethylene production. In fact, low concentrations of salicylic acid stimulated rather than inhibited ethylene production. The results show that in suspension‐cultured cells, caution is warranted in the interpretation of results obtained with agents presumed to inhibit ethylene biosynthesis. The stimulation of somatic embryogenesis by ethylene unequivocally shows that the inhibition of embryo development by 2.4‐dichlorophenoxyacetic acid (2.4‐D) and other auxins cannot be through their stimulatory effect on ethy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08827.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The growth and development of protoplasts of rapeseed (Brassica napusL. cv Line) and carrot (Daucus carotaL. cv. Navona) were studied onboard the Space Shuttle‘Discovery’during an 8‐day International Microgravity Laboratory [IML‐l) mission in January 1992. The Flight experiments were carried out in‘Biorack'. a fully controlled cell biological experimental facility. under microgravity conditions and in a l‐g centrifuge. Parallel experiments were performed in a‘Biorack’module on the ground. After retrieval, some samples were subcultured on appropriate media and analysed for callus growth and regeneration to intact plants. The remainder were used for biochemical analysis. Samples fixed on board the Space Shuttle were kept in l% glutaraldehyde fixative at 4°C for 3–7 days for microscopy analysis after retrieval. Protoplasts exposed to microgravity conditions showed a delay in cell wall synthesis. Cells were swollen in appearance and formed cell aggregates with only few cells. Callus were obtained from protoplasts cultured under microgravity (Fogl). on the l‐g centrifuge on board the shuttle (Flg), under normal l‐g conditions on the ground (G1g) and on a centrifuge on the ground giving 1.4 g (Gl.4g). Regeneration of intact rapeseed plants was obtained from Flg. Glg and G1.4g. However, no plants were regenerated from protoplasts exposed to microgravity (Fog). Biochemical analysis indicated that the microgravity samples (Fog displayed a reduced packed cell volume, an increased concentration of soluble proteins per cell, and a reduced specific activity of peroxidase in the cytoplasm. Morphometric analysis of fixed samples demonstrated that 3‐day old protoplasts under microgravity conditions were significantly larger than protoplasts kept on the l‐g centrifuge in space. UItrastructural analysis by transmission electron microscopy showed that protoplasts exposed to microgravity conditions for 3 days had larger vacuoles and a slightly reduced starch content compared to Flg cells. Cell aggregates formed under microgravity conditions (Fog) had an average of 2–I cells per aggregate while aggregates for

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08828.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In order to optimize transient gene expression in Norway spruce pollen after DNA delivery with particle bombardment, effects of different conditions during homhardmenl were analysed using β‐glucuroniduse (GUS) driven by the riceActI promoter and Inciferase (LUS) driven by the tomato!at52 promoter as reporter genes. Transient gene expression was significantly increased hy using two bombardments. Also the distance from the stopping plate to the sample was critical to gam maximum gene expression. There was no significant difference between gold and tungsten particles, and the number of positively stained pollen increased with increasing DNA concentration, from 5 to 40 pg DNA added in the DNA/tungsten solution The DNA delivery to Norway spruce pollen was most efficient at a chamber pressure above 70 k

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08829.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A hurst of hydrogen peroxide has been found in the red macroalgaEucheuma platycladwnSchmitz as a response to mechanical stress. After exposure of pieces of thalli (2 cm) broken from the plant and stirred with a magnetic bar an oxidative burst was registered, as measured by luminol dependent chemiluminescence (LDC). The burst was totally inhibited by cataluse (EC 1.11.1.6). showing the generation of H2:O2;Ten g of seaweed in 300 ml sea water caused a maximal medium concentration of LDC corresponding to 7 u.MH2O2;The burst decayed after about 30 min. The decay is probably caused by increased catalase aciivity of the sea water. due to leakage of catalasc from the seaweed. Addition of NaN3caused a dramatic increase in LDC. probably due to inhibition of catalase. Similar bursts of active oxygen, involving active oxygen species such as O2, H2O2and OH. have been reported as pan of the hypcrsensitive reaction in some higher plants, e.g. tobacco. potato and soybean. Exposure of plants or cell suspension cultures to some pathogenic bacteria, fungi, inorganic elicitors or physical damage causes an oxidalive burst that is often followed by necrosis. The production ot active oxygen is thought to he a first defence against invading pathogens. We assume that the oxidative burst fromE. platycladumis of a defensive nature, providing a protection against grazers and pathogenic organisms. To our knowledge this is the first repoil of an oxidalive burst from seaweeds.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08830.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Chlorophyll fluorescence and gas‐exchange techniques were used to investigate changes in photosynthelic performance in response to high light and mild water deficit, in two cultivars of the C., plant sorghum (Sorghurn bicofor[L.] Moench). grown under field conditions. For all leaves fully exposed to the sun, the efficiency of phcttosystem 11 (PSII) showed a mid‐day decline, hut with substantial over‐night recovery: the magnitude of the mid‐day decline was enhanced by water deficit. There was no corresponding decline in leaves not exposed to full sunlight, either because they were shaded by other leaves or else because of leaf‐roiling. Net assimilation rates appeared more sensitive to water‐deficit than was PSI1 efficiency. Shade‐adapted leaves had lower rates of photosynthesis in full sun (and lower stomatal conductances) than well‐exposed leaves. When these shade‐adapted leaves were suddenly exposed to full sunlight, fluorescence quenching was slow. especially when plants were well‐watered. For the latter, photochemical quenching (qp)was small even after several minutes. indicating a continuing imbalance between energy funnelled to PSI1 and subsequent electron transport. Shade‐adapted leaves that were water stressed were better able to withstand a sudden increase in irradiance than those that were well watered. It is suggested that the shade‐adapted eaves from unirrigated plants. having a lower s'tomatal conductance than the irrigated leaves, had been acclimated by receiving energy in excess of that required to fix CO2, thus leading to the operation of dissipative mechanisms. A shortened protocol for quenching analysis is proposed that enables non‐photochemical quenching to be partitioned into rapidly and slowly relaxing components (the latter including photoinhibition) by relating results to a theoretical maximum yield of variable fluorescence. This is particularly suitable for

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08831.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Stems ofThryptomene vaxicola(A. Cunn.) Shau. cut in air and immediately placed in water at 20°C showed ultrasonic acoustic emissions after 8 to 12 h. whereas no emissions were found inThryptomene catycinaLindl.) Stapf, within 100 h. Stem water potential declined in a similar manner in both species: a high frequency of acoustic emissions stalrted at approximately –1 000 kPa in T.saxicola., but had not commenced at –5300 kPa inT. calycina. The rates of water uptake were similar in both species. Acoustic emissions in T.saxicolaplaced in water were prevented h recutting 15 cm of the stems under water.For comparison, cut stems which were air‐dehydrated at 20°C exhibited a primary peak in the frequency of emission after 3–5 h in T.saxicolaand 15 h in T.catycina, corresponding to a water potential of –1000 kPa and less than –5000 kPa. respectively. After 6. 16. and 24 h of dehydration in air and subsequent placement in water for 24 h. the rates of water uptake of T.calycinawere not lower than in controls not held dry, How ever. in T.saxicolawater uptake rates had decreased after 16 h of dehydration and were very low after 24 h.The results show that ultrasonic acoustic emissions may occur in freshly cut stems placed in water, and that they occur at a water potential similar to that in stems allowed to dehydrate in air. The number ol emissions in T.saxicolastems placed in water was apparently too low to inhibit water uptake. When held dry. the cavitated xylem elements may be a cause of reduced water uptake

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08832.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY