Cytoplasmic Channels and Chromatin Migration in the Meiocytes of Arnebia hispidissima (Sieb.) DC

Microsporogenesis was studied in Arnebia hispidissima whichprovided interesting evidence for the occurrence of cytoplasmicchannels and DNA migration between the meiocytes. The intercommunicatingchannels (0.25–1.75 µ in diameter) are consideredto be a prerequisite for chromatin migration and to act as pathwaysbetween the connected meiocytes. They may develop at any stageof meiosis from early prophase to metaphase II and the migrationmay take place at any time following channel formation. Thetendency of chromatin to migrate seemed to be higher in theearly prophasic stages when it moved in the form of ill-definedmasses or clumps. The chances of migration as well as the amountof migrating chromatin is reduced as the meiosis advances. Theamount of chromatin migrating varies from a small portion tothe entire chromatin mass or nucleus. Pollen mother cells withdouble the normal amount of chromatin as well as those withlittle or none were studied as well as cells with increasedor decreased chromosome numbers. In the chromatin mass, uni-or bivalents stretched between the meiocytes or attenuated towardsthe channel, were frequently seen. Occasional semi-asyndesis,multivalent formation, precocity, and nondisjunction was alsonoted. The possibility of channel formation and the induction of chromatinmovement as a consequence of mechanical or procedural defectis ruled out. It is believed that these cytoplasmic channelshave no relation with the plasmodesmata but they arise de novoand that chromatin migration occurs as a natural phenomenon(in some species). The observations are not due to faulty fixation,staining, or squashing.     

Genetic analyses for deciphering the status and role of photoperiodic and maturity genes in major Indian soybean cultivars

Allelic combinations of major photoperiodic (E1, E3, E4) and maturity (E2) genes have extended the adaptation of quantitative photoperiod sensitive soybean crop from its origin (China ～35 ^°N latitude) to both north (up to ～50 ^°N) and south (up to 40 ^°S) latitudes, but their allelic status and role in India (6–35 ^°N) are unknown. Loss of function and hypoactive alleles of these genes are known to confer photoinsensitivity to long days and early maturity. Early maturity has helped to adapt soybean to short growing season of India. We had earlier found that all the Indian cultivars are sensitive to incandescent long day (ILD) and could identify six insensitive accessions through screening 2071 accessions under ILD. Available models for ILD insensitivity suggested that identified insensitive genotypes should be either e3 /e4 or e1 (e1-nl or e1-fs) with either e3 or e4. We found that one of the insensitive accessions (EC 390977) was of e3 /e4 genotype and hybridized it with four ILD sensitive cultivars JS 335, JS 95-60, JS 93-05, NRC 37 and an accession EC 538828. Inheritance studies and marker-based cosegregation analyses confirmed the segregation of E3 and E4 genes and identified JS 93-05 and NRC 37 as E3E3E4E4 and EC 538828 as e3e3E4E4. Further, genotyping through sequencing, derived cleaved amplified polymorphic sequences (dCAPS) and cleaved amplified polymorphic sequences (CAPS) markers identified JS 95-60 with hypoactive e1-as and JS 335 with loss of function e3-fs alleles. Presence of photoperiodic recessive alleles in these two most popular Indian cultivars suggested for their role in conferring early flowering and maturity. This observation could be confirmed in F ₂ population derived from the cross JS 95-60 × EC 390977, where individuals with e1-as e1-as and e4e4 genotypes could flower 7 and 2.4 days earlier, respectively. Possibility of identification of new alleles or mechanism for ILD insensitivity and use of photoinsensitivity in Indian conditions have been discussed.     

A MUCILAGE-FORMING LACTOBACILLUS SPECIES ISOLATED FROM CIDER. PART I. CHARACTERISTICS

SUMMARY: A rod-shaped, facultative, heterofermentative lactic acid-forming microorganism, isolated from cider, showed some similarities to Lactobacillus pastorianus van Laer, to L. pastorianus var. brownii and to L. brevis Orla-Jensen. Its most notable characteristic was an ability to form mucilage in a medium containing glucose, fructose or especially maltose. The highest levels of viscosity were obtained in a medium containing maltose (pH 5·1), after 12–16 days incubation at 25° under an atmosphere of carbon dioxide.     

The Influence of Varying Concentrations of Applied Sugar on the Transport of Tracers in Cereal Leaves

When young leaves of rye which have been emptied of mobile carbohydrateby darkening have ¹³⁷Cs applied to their apices, it is foundthat the tracer only moves, in the darkened plant, when sugaris applied at the same time. If a treated leaf is harvestedafter a suitable interval, cut into sections, and assayed forradioactivity, the usual pattern of exponential fall-off withdistance is found. On a plausible mass-flow model the negativeslope of the semi-logarithmic plot is simply related to thetransport velocity and to the rate of lateral leakage out ofthe conducting channels. This slope has been investigated asa function of the concentration of the applied sucrose, andit is found to vary as the fifth or sixth root of the latter.When ³⁰C1 is used as tracer the slope appears to have a consistentlyhigher value than in the case of ¹³⁷Cs. In both cases, and alsowhen ¹⁴C lactose is used with lactose as the activating sugar,the semi-logarithmic plot is concave upwards. The significanceof these findings is discussed.     

Effect of Prolonged Geo-stimulation and Presence of 32P on the Elongation of Lateral Shoots of Decapitated Pea Seedlings

The effects of prolonged geo-stimulation and presence of ³²P on 3-leaf decapitated pea (Pisum sativum L. cv. Alaska) seedlings were studied with regard to lateral bud elongation as well as accumulation and recovery of isotope. Prolonged geo-stimulation favoured the dominance of basally located, upwardly directed buds and suppressed the elongation of subapical bud — a gravimorphic response similar to the one shown by intact geo-stimulated branches of woody plants. Basal bud 2 was an exception as it dominated both in the above- and below-axis position. Accumulation of ³²P in buds was the result of their own growth, whereas in the other parts of the seedlings accumulation of isotope was not necessarily related to growth. Geo-stimulation affected ³²P recovery in redistribution experiments, whereas it had no effect in distribution experiments. In the former, the decrease in the isotope level in the seedling suggests a loss of ³²P. Prolonged presence of ³²P in the seedlings had a deleterious effect on bud elongation.     

Water Stress and Apical Morphogenesis in Barley

The formation of new primordia on the apical meristem of barley(Hordeum vulgare L.) was inhibited at levels of soil water potential(-1 bar and less) which had little or no effect on growth ofthe plant. Both leaf growth and morphogenesis of lateral spikeletson the developing ear proceeded at reduced rates at water-potentiallevels which completely suppressed primordium formation. Thissensitivity of the apex to stress was unaffected by floral initiationand was apparently not due to changes in water potential inthe apical tissues. Primordium formation was inhibited eventhough apical water potential was unchanged. Water stress suppressedthe response of the apical meristem to an increase in the photoperiodto which the plant was exposed. In some circumstances, however,the photoperiodic response was displayed after the stress wasrelieved. During an episode of moderate water stress it waspossible to observe an increase in the rate of primordium formationin response to an increase in light intensity.