An enzyme-linked immunosorbent assay for phytochrome

A double-antibody sandwich, enzyme-linked immunosorbent assay has been developed for phytochrome in Avena sativa L. cv. Saladin. An immunoglobulin fraction of rabbit antiserum raised to 118 kdalton phytochrome was used with alkaline phosphatase as the enzyme label. The assay detected as little as 0.2 ng phytochrome in extracts of dark-grown plant material. No evidence for specific or non-specific measurement of proteins other than phytochrome was found. The assay detected phytochrome in extracts of Avena grown in the light. Dilution curves for light-grown phytochrome extracts had a reduced slope and saturated at a lower level of enzyme activity than those for dark extracts. These differences were not caused by an inhibitor in extracts from light-grown plants. Phytochromes from dark- and light-grown plants may be immunologically different.     

Static electric fields do not cause coleoptile movements

A photodiode array method has been used to record automatically minute lateral movements of Avena sativa L. (cv. Seger I) coleoptiles in a static electric field. The electric fields, 600 or 5000 V cm⁻¹ did not cause any significant movement of the coleoptiles, in contrast to reports in the literature. Likewise, in experiments where photographic recordings were made, no significant movements were found.     

小麦细胞分裂间期外源染色质的检测

以野生种基因组ＤＮＡ为探针，用荧光原位杂交研究了间期细胞核里黑麦，中间偃麦草，燕麦和簇毛染色体在普通小麦背景下的行为，易位的黑麦１ＲＳ染色体襞在间期表现为不连续的线状杂交信号贯穿细胞核，代换和附加的１Ｒ染色体在间期却呈现点状杂交信号，通过易位进入小麦的中间偃麦草和燕麦染色体片段也是点状。     

The effects of diclofop-methyl on root growth of wild oat

Diclofop-methyl severely reduced the growth of seminal roots of wild oat ( Avena fatua L.) when applied in hydroponics at 0.01 and 0.05 μ M . Lateral roots emerged closer to the seminal root apex than in the controls, but coronal root number and length were unaffected at 0.01 μ M . However, doses of 0.05 to 0.1 μ M induced more but shorter coronal roots to emerge than for controls. At 1 μ M the number and length of coronal roots were less than for controls. Root-applied diclofop-methyl at 1 μ M inhibited emerging second leaf growth to the same extent as a foliar dip in 1 μ M diclofop-methyl without causing chlorosis as foliar treatment does. Because of limited basipetal transport of foliarly-applied diclofop-methyl, shoot treatment was ineffective in inducing abnormal root morphogenesis of the seminal and lateral root systems, although it caused abnormalities of the coronal root system. Time course studies were initiated to examine the effect of root-applied diclofop-methyl at 0.05 μ M . Seminal root growth was inhibited (by diclofop-methyl) soon after treatment, while controls continued elongating. The distance between the seminal root apex and the first lateral primordia increased in the controls within one day after treatment, but decreased in the herbicide-treated roots. The distance between the seminal root apex and the first emerged lateral root was reduced by three days after treatment. The number of lateral primordia and emerged roots was unaffected three days after treatment. These dose-response and kinetic results suggested that diclofop-methyl caused a loss of apical dominance in the seminal root.     

Plant responsiveness to variation in precipitation and nitrogen is consistent across the compositional diversity of a California annual grassland

Question: How does responsiveness to water and Nitrogen (N) availability vary across the compositional and functional diversity that exists in a mesic California annual grassland plant community? Location: Northern California annual grassland. Methods: A mesocosm system was used to simulate average annual precipitation totals and dry and wet year extremes observed in northern California mesic grasslands. The effects of precipitation and N availability on biomass and fecundity were measured on three different vegetation types, a mixed grass forb community, and a forb and a grass monoculture. The treatment effects on plant community composition were examined in the mixed species community. Results: While growth and seed production of the three vegetation types was inherently different, their responses to variation in precipitation and N were statistically similar. Plant density, shoot biomass, and seed production tended to increase with greater water availability in all vegetation types, with the exception of a consistent growth reduction in high precipitation (1245 mm) plots in the first year of the study. Shoot biomass responded positively to N addition, an effect that increased with greater water availability. Nitrogen addition had little effect on plant density or seed production. In the mixed grass‐forb community, biomass responsiveness to water and N treatments were consistently driven by the shoot growth of Avena barbata, the dominant grass species. Conclusions: Vegetation responses to changes in precipitation and N availability were consistent across a range of composition and structural diversity in this study. Plant growth and seed production were sensitive to both increased and decreased precipitation totals, and the magnitude of these responses to N availability varied depending on soil moisture conditions. Our results suggest the impacts of changing precipitation regimes and N deposition on annual productivity of California grasslands may be predictable under different climate scenarios across a range of plant communities.     

Carbohydrate partitioning between upper and lower regions of the crown in oat and rye during cold acclimation and freezing

Carbohydrates have long been recognized as an important aspect of freezing tolerance in plants but the association between these two factors is often ambiguous. To help clarify the relationship, the allocation of carbohydrates between specific tissues within the over wintering organ (crown) of winter cereals was measured. A winter-hardy and non-winter-hardy oat (Avena sativa L.), and a rye (Secale cereale L.) cultivar were grown and frozen under controlled conditions. Crown tissue was fractionated into an upper portion, called the apical region, and a lower portion, called the lower crown. These tissues were ground in liquid N and extracted with water. Extracts were analyzed by HPLC for the simple sugars, sucrose, glucose, fructose, and for fructan of various size classes. After 3 weeks of cold acclimation at 3 degrees C, carbohydrates accounted for approximately 40% of the dry weight of oats and 60% of the dry weight of rye. The apical region, which is the tissue within the crown that acclimates to the greatest extent, was generally 10% higher in total carbohydrates than the lower crown. During a mild freeze, various carbohydrates were allocated differently between specific tissues in the three genotypes. When frozen, fructan generally decreased to a greater extent in the lower crown than in the apical region but sugars increased more in the apical region than in the lower crown. Results suggest that to understand how carbohydrates relate to freezing tolerance, regions of the crown that endure freezing stress differently should be compared.     

Characterisation of cDNAs for ribulose bisphosphate carboxylase small subunit genes in different species of Avena (Poaceae)

ABSTRACT

We report the cloning and sequencing of 14 rbcS cDNAs in six species of Avena (Poaceae) with different genome and ploidy levels. The nucleotide sequences 504 bp long were aligned with the published sequences of cultivated hexaploid oat, wheat, barley, rye, rice and corn and subjected to cladistic and phenetic analyses. The parsimonious analysis generated a tree with a topology very similar to the phenogram generated by the Neighbor-Joining analysis based on the Jukes and Cantor distances. Within the monophyletic assemblage of the tribe Aveneae, consistent clades composed of rbcS clones belonging to different species are recognized. It is suggested that they correspond to orthologous genes belonging to different subfamilies, and that the “within-species?d homogenisation may have occurred at a slow rate with respect to species evolution. In the monophyletic group of Pooideae, the topologies place barley rbcS sequences closer to wheat and rye than to oat sequences. This grouping agrees with most taxonomic and phylogenetic views.     

Identification and genetic characterisation of adult plant resistance to crown rust in diploid and tetraploid accessions of Avena

The identification and genetic characterisation of adult plant resistance (APR) to crown rust, caused by Puccinia coronata f. sp. avenae (Pca), was carried out in diploid Avena strigosa and tetraploid Avena barbata accessions from diverse geographical regions. Seven accessions were found to carry APR to Pca, six of which (CIav6956, CIav7280, CIav8089, CIav9020, PI292226, PI436082) were diploid and one (PI337865) a tetraploid. All six diploid A. strigosa accessions were postulated to carry the ‘Saia’ seedling resistance to Pca (Pc15, Pc16, Pc17) in addition to the APR. Three of these six accessions (CIav6956, CIav9020, PI292226) were used to study both seedling resistance and APR, using two Pca pathotypes, one avirulent on seedlings and the second virulent on seedlings but avirulent on adult plants. The seedling resistance in each was shown to be inherited independently of the APR. In each case, APR was conferred by a single major dominant gene, based on hypersensitivity, coupled with low infection types. Allelism tests are required to determine if these three APR genes are different. This is the first report of APR to crown rust in A. strigosa and A. barbata.     

Nuclear magnetic resonance imaging in studies of gravitropism in soil mixtures

Gravitropic responses of oat coleoptiles were measured in different growth media; humid air, natural soil and artificial soil (glass beads). The oat coleoptiles in soil and glass beads were monitored by NMR imaging, while those in humid air were imaged in darkness with an infrared-sensitive charge-coupled device (CCD) camera. The present study shows for the first time that gravitropic experiments can be performed in artificial soil using NMR imaging as a convenient and suitable recording method. Not only was it possible to follow the gravitropic curvatures in natural soil, but the artificial soil allowed plant images of sufficient spatial and temporal resolution to be recorded. The advantages of using artificial soil in magnetic resonance imaging studies are that the iron content of glass beads is very low compared with natural soil, and that the artificial soil matrix can easily be standardized with regard to particle size distribution and nutrient content. Two types of glass beads were used, the diameter of the small and the large beads being 300–400 and 420–840 μm, respectively. The growth rate of the coleoptiles in soil and in big beads was roughly the same and only slightly lower than in humid air, whereas small beads reduced the growth rate by approx. 16%. The bending rate of the coleoptiles during the gravitropic response was reduced by c. 65% in soil and 75% in bead mixtures relative to bending in air. It should be noted, however, that the maximum curvature of the coleoptile tip was of the same order in all cases, about 35°. This value may represent the largest possible curvature of the organ. The potential of NMR imaging to study how plant organs penetrate the soil under the influence of gravitropism, mechanical impedance and thigmotropism is also discussed.     

一粒小麦×野燕麦衍生系细胞学特征及条锈病抗性鉴定

在一粒小麦与葡萄牙野燕麦远缘杂交后代中,选育了5个形态学稳定的抗条锈病衍生系(‘一粒葡’)YLP-1、YLP-7、YLP-9、YLP-13和YLP-16,为筛选含有外源染色体且抗性优良的植株,对该衍生系的细胞学特征和抗病性进行了鉴定。细胞学初步鉴定表明:根尖染色体数目均为2n=42,花粉母细胞减数分裂中期Ⅰ染色体构型为2n=21Ⅱ;5个选系与‘中国春’杂交F1花粉母细胞减数分裂中期Ⅰ的异常细胞构型率为16%～50%;初步鉴定这5个‘一粒葡’材料均为易位系,验证了‘一粒葡’是远缘杂交的后代。用9个条锈菌小种分别对9个株系进行苗期抗病性鉴定,有5个株系YLP-1-4、YLP-7、YLP-9-1、YLP-9-3、YLP-16-1对所有参试小种都表现为高抗,且与已知的Yr5、Yr10、Yr15、Yr24/Yr26基因不同,表明‘一粒葡’中可能含有新的抗病基因,可作为抗源用于小麦抗病育种。