Flowering of S. 24 Perennial Ryegrass (Lolium perenne L.) in Short Days at Low Temperature

The flowering of the quantitative long-day plant perennial ryegrass(Lolium perenne L.) in short days (8 h), when grown at low temperature(9/4 °C) and under natural summer daylight, is presentedas evidence for the replacement of specific environmental requirementsfor flowering by alternative stimuli in a grass.     

Phases of Development to Flowering in Opium Poppy (Papaver somniferumL.) under Various Temperatures

Development up to flowering in opium poppy (Papaver somniferumL.)has been divided into four phases from emergence to anthesiswhich mark changes in its sensitivity to photoperiod: a photoperiod-insensitivejuvenile phase (JP), a photoperiod-sensitive inductive phase(PSP), a photoperiod-sensitive post-inductive phase (PSPP) anda photoperiod-insensitive post-inductive phase (PIPP). To predictflowering time under field conditions, it is essential to knowhow these phases are affected by temperature. Plants were grownin artificially-lit growth chambers and received three differenttemperature treatments: 15/10, 20/15 and 25/20 °C in a 12h thermoperiod. Plants were transferred within each temperatureregime from a non-inductive 9 h to an inductive 16 h photoperiodorvice versaat 1–4 d intervals to determine the durationsof the four phases. Temperature did not affect the durationof the first two phases (i.e. JP lasted 3–4 d and PSPrequired 4–5 d). The most significant effect of temperaturewas on the duration of PSPP which was 28, 20 and 17 d at 15/10,20/15 and 25/20 °C, respectively. The temperature effecton PIPP was small (maximum difference of 3 d between treatments)and the data too variable to indicate a significant trend. Ourresults indicate that PSPP is the only phase that clearly exhibitssensitivity to temperature. Days to flower; opium poppy; Papaver somniferumL.; phases of flower development; photoperiod; temperature     

Flowering and gibberellins in a mutant red clover (Trifolium pratense L.)

Relationships between gibberellins and floral initiation were investigated in a conditional non-flowering mutant of red clover, Trifolium pratense. Untreated mutant plants will not flower under long-days, but will do so when certain GAs are applied. Gibberellins, A₃, A₁, A₇, and A₅ all resulted in both stem elongation and flowering whilst GA₄ produced the elongation only. Applications of GA₂₀, GA₈ and GA₁₃ under long-days had no detectable effect. Thus, by combining the use of the mutant with the application of different GAs, the correlation between the processes of stem elongation and floral initiation, which is normally strongly expressed in this species, was broken. Endogenous gibberellins shown to be present in normal plants were also found in the mutant genotype. Gibberellins alone were not sufficient to initiate floral development in the mutant, there being an essential element of interaction with long-days. These results are discussed in relation to the nature of the lesion in the mutant and the signal provided by the applied gibberellin.     

Silicon in Imperata cylindrica (L.) P. Beauv: content,distribution, and ultrastructure

Silicon concentration, distribution, and ultrastructure of silicon deposits in the Poaceae Imperata cylindrica (L.) P. Beauv. have been studied. This grass, known for its medicinal uses and also for Fe hyperaccumulation and biomineralization capacities, showed a concentration of silicon of 13,705?±?9,607 mg/kg dry weight. Silicon was found as an important constituent of cell walls of the epidermis of the whole plant. Silica deposits were found in silica bodies, endodermis, and different cells with silicon-collapsed lumen as bulliforms, cortical, and sclerenchyma cells. Transmission electron microscope observations of these deposits revealed an amorphous material of an ultrastructure similar to that previously reported in silica bodies of other Poaceae.     

Growth of Perennial Ryegrass (Lolium perenne L.) Exposed to a Low Concentration of Sulphur Dioxide

The influence of a low concentration of SO₂ on the growth andsulphur status of perennial ryegrass (Lolium perenne L.) cv.S23 was examined in a system of specially designed growth chambers.For plants grown without additions of sulphate to the soil,erposure to ifitered air containing 50 µg m^–3 SO₂alleviated sulphur deficiency that developed during a sequenceof successive harvests, and gave increased yield. The plantshad higher contents of organic and inorganic sulphur than thosegrown with neither sulphate nor SO₂. Plants grown with addedsulphate showed no signs of sulphur deficiency and althoughexposure to SO₂ increased their sulphur content it had no effecton yield. The coefficient of transpiration (g water transpiredg^–1 dry wt. of shoots) was reduced when plants which otherwisehad an inadequate supply of sulphur were exposed to SO₂; forplants with adequate supplies of sulphate, it was similar whetherthey were grown with or without the addition of SO₂ to the air.The results are discussed in relation to other known reactionsof plants to SO₂.     

Gibberellins and Inhibitors in Relation to Flowering of White Clovers (Trifolium repens L.)

Flower primordia appeared sooner and flowering intensity increasedas day length was extended beyond 8 h (short day) in two whiteclovers: cv. Tamar and cv. Tammisto, originating from Israeland Finland, respectively. Application of GA₃ under short dayscaused Tamar to flower more intensively as much as the doseof GA₃ was increased, but it did not affect the flowering ofTammisto. The level of gibberellin-like substances in stolon apices washigher under long (16 h) than under short days in both cultivars.The level of inhibitors extracted from leaves was not affectedby day length in Tamar. However, in Tammisto this level wasalmost twice as high under short than under long days. It issuggested that the presence of a relatively high level of inhibitorsin Tammisto when grown under short days interfered with theactivity of gibberellins in its effect on flowering. ABA wasamong the inhibitors: its application under long days had noeffect on flowering, but it increased the number of stolons.Possibly inhibitors other than ABA are involved in the preventionof flowering. Leaf expansion responded to day length and GA₃ and ABA applicationin a similar way as the response of flowering, i.e. towardsflowering the size of the leaves increased.     

Monthly variations in calix growth, polyp tissue, and density banding of the Mediterranean scleractinian Cladocora caespitosa (L.)

Monthly skeletal growth of the scleractinian, temperate coral Cladocora caespitosa (L.) from the Ligurian Sea (NW Mediterranean) was analysed for a period of 1 year and compared with seawater parameters. Measurements on corallite sections and on X-ray images showed that the formation of the high-density (HD) band and two dissepiments are favoured by fall–winter conditions, characterised by high quantities of rain, rough seas, and cold seawater. In summer, when the low-density (LD) band is formed, the corallites stretch upward and form one new dissepiment and one deep calix, where the polyps recede almost completely in August. These findings confirmed the adaptation of the temperate coral to winter environmental conditions, characterised by low irradiance and high availability of nutrients and food particles resuspended from bottom sediments. On the contrary, the high seawater temperature, irradiance, and ammonia contents stressed the coral in August and, when they persist in September, may cause the onset of mortality events.     

Leaf Abscission Zones in Molinia caerulea (L.) Moench, the Purple Moor Grass

Leaf separation and loss in the grass Molinia caerulea (L.)Moench was investigated using scanning electron microscopy.Leaf senescence and subsequent shedding of leaves was precededby the formation of a leaf abscission zone. The zone containscells which have more than doubled their wall thickness to greaterthan 0-4 µm. The line of fracture associated with thezone principally followed the middle lamellae, leaving intactcells on the fracture faces. Molinia should prove an interestingmodel in which to study abscission processes in the Gramineae. Molinia caerulea, leaf abscission zone, electron microscopy     

Genes controlling prolamin biosynthesis, Pro1 and Pro2, in foxtail millet, Setaria italica (L.) Beauv

Variation and genetic control of seed protein in foxtail millet (Setaria italica) were studied using SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Variation in the electrophoregram of the total seed protein were detected in the range between 20 and 30 kDa which is derived from the polymorphism of five prolamin bands. The segregation for each of the bands in F2 seeds showed that these bands are governed by seven alleles at two loci, Pro1 and Pro2, which are not linked to one another. Among 271 local cultivars examined, eight out of ten possible genotypes were observed. With its level of diversity comparable to that of isozymes, the alleles conferring prolamin polymorphism are useful genetic markers.     

Variation,geographical distribution and genetical analysis of esterase isozymes in foxtail millet,Setaria italica (L.) P. Beauv.

Summary The esterase isozymes of 432 strains of foxtail millet, Setaria italica (L.) P. Beauv., collected from different areas throughout Eurasia, were investigated by gel isoelectric focusing. Five phenotypes were recognized, based on the combination of five major activity bands. Cross experiments among different phenotypes revealed these isozymes to be controlled by two codominant alleles and a null allele on the locus, Est-1, and three codominant alleles on another independent locus, Est-2. On locus Est-1, 388 strains had Est-1 ^a, 41 had Est-1 ^b and three had Est-1 ^null alleles. Est-1 ^a was widely distributed throughout Eurasia, while the distribution of Est-1 ^b and Est-1 ^null was distinctly restricted. On locus Est-2, 417 strains had Est-2 ^a, nine had Est-2 ^b and six had Est-2 ^c alleles. Est-2 ^a was widely distributed throughout Asia to Czechoslovakia, but was not detected in the western part of Europe. Est-2 ^b was found in all of the strains from the western part of Europe and in one of the Indian strains. Est-2 ^c was rarely found in Japan and China. The distribution of Est-2 ^a and -2 ^b might indicate some degree of phylogenetic differentiation between the Asian and the European strains. Polymorphism in both loci was observed only in Chinese strains.Contribution No. 30 from the Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan     

Mortality of Immature Houseflies (Musca domestica L.) in Artificial Diet and Chicken Manure after Exposure to Encapsulated Entomopathogenic Nematodes (Rhabditida: Steinernematidae, Heterorhabditidae)

The entomopathogenic nematodes, Steinernema felitae (=bibionis) and Heterorhabditis megidis, were encapsulated in calcium alginate and their efficacy was tested against immature houseflies. Aliquots of capsules (15 ml) containing either 1 000 000, 500 000, 250 000 or 125 000 nematodes were added to 70-ml portions of grassmeal diet containing either eggs of first, second or third instar larvae. After 2 days, the treatment with 1 000 000 encapsulated S. feltiae (=bibionis) had killed 94% of housefly eggs and 90% of first instar larvae. By day 6, both of these mortalities had increased significantly (P 0.005) to 100%. By day 2, in the same medium, 1 000 000 encapsulated H. megidis had killed 71.4% of eggs and 90% of first instar larvae. This increased significantly (P 0.01) by day 6, to 99.2% and 100% respectively. Another experiment was carried out where immature houseflies were placed in chicken manure. The emergence of houseflies as adults was used to measure the effect of the encapsulated nematodes. Depending on the numbers of nematodes and the original stage of the housefly, the treatment with encapsulated S. feltiae resulted in 55-96% reduction in adult housefly emergence, whereas treatment with encapsulated H. megidis resulted in 35-98% reduction in emergence. Finally, when encapsulated nematodes were presented as a bait to adult houseflies, little infectivity was observed.