Sodium and Cation Accumulation by Senna (Cassia acutifolia)

Senna plants, native to the arid parts of the northern Sudan,were analysed for mineral cations. Plants tended to accumulate salts in tops, particularly whengrowing in saline soils. Highest concentrations of salts (mostlyCa and Na) were in the leaves with a gradient from bottom totop leaves. Variation in the cation sum was associated withboth Ca and Na contents. Under high salinity, plant growth was reduced without injurysymptoms, but with shedding of some lower leaves. The same symptomswere also noted in plants subjected to soil moisture stress.It is therefore postulated that lower leaf shedding is a physiologicalmeasure for reducing plant salt level and transpiration.     

Floral biology and pollen viability of parental lines of onion hybrids

Parental lines (inbred and hybrid male-sterile lines and inbred pollinators) of prospective F, hybrids from the NVRS spring-sown bulb onion breeding programme were examined to study their floral biology and aspects of pollination under glasshouse conditions. Inbreeding depression occurred in both pollinator and male-sterile inbreds in terms of reduced flower numbers per umbel and a greater proportion of defective pistils. Male-sterile and male-fertile lines differed in their stigma and style characteristics and pattern of development. At flower opening, the styles of male-sterile lines were longer and the stigmatic knob became receptive relatively sooner. The inbred male-sterile line II/3 ms appeared to have a reduced receptive area on its stigmatic knob and remained receptive for a relatively shorter period. Individual lines differed for time of flowering, nectar content and its sugar concentration, and in their effectiveness as male and female parents as judged from pollen tube growth down the style in specific pairings. Assessment of pollen viability using the fluorescein diacetate test did not correlate with assessments based on pollen grain germination and subsequent growth down the style, perhaps as a result of differential receptivity in the inbred lines tested. These results are discussed in relation to future hybrid seed production.     

Immunization by Irradiated Eimeria acervulina

SYNOPSIS. In 5 experiments the infectivity and immunogenicity for chickens of sporulated oocysts of Eimeria acervulina that had been previously subjected to different levels of gamma radiation was tested. It was found that the irradiation doses can be divided into three groups: a) High dosage levels of over 16,000 rad impair the reproduction of the parasites so that few or no oocysts are discharged and no immunity is produced. b) Low dosage levels of 7,000 rad and less permit reproduction and development of immunity not perceptibly different from that resulting from unirradiated oocysts. c) An intermediate range of levels with the optimum from 9,100–13,700 rad induces attenuation while at the same time assuring sufficient immunogenic response.
A dose of 100,000 oocysts or more per bird is required to produce immunity. The optimum irradiation dose increases with the immunizing dose. It was concluded that the development of an irradiated vaccine is possible.     

Some Primary Features of Salt Tolerance in Senna (Cassia acutifolia)

Studies on the germination of Cassia acutifolia (senna) seedsindicated, that they were highly tolerant of salinities up to16.0 mmhos cm^–1, and 50 per cent reduction in germinationoccurred, at about 20.0 mmhos cm^.1. Air temperature had a significanteffect on senna germination at substrate salinities between10.0 and 25.0 mmhos cm^–1. Seedling growth was more sensitive to salinity and alkalinitythan the germination stage. Young plant survival and total podyield were significantly reduced in soil salinities higher than11.0 minhoa cm^–1, and this was more pronounced when plantswere irrigated at short intervals with saline waters. The sensitivityof senna to higher levels of salinities was correlated withthe higher rate of chloride accumulation in the tissue resultingin specific chloride injury. However, the possibility of sodiuminjury cannot be excluded.     

Changes in Carbohydrates and Enzyme Activities in the Roots during the Forcing of Virus-free Timperley Early Rhubarb

Changes in the roots of the carbohydrates and some of the enzymesinvolved in their metabolism have been measured during the forcingof virus-free Timperley Early rhubarb in which the dormancyhad previously been broken by cold treatment. The amount ofsucrose decreased throughout forcing; this mainly occurred duringthe first 7 days. Starch increased during the early stages offorcing and thereafter remained constant. The reducing sugars,glucose and fructose remained throughout at a fairly low andconstant amount. Sucrose synthetase activity remained almostconstant for about 10 days of forcing and then decreased, whilstphosphorylase activity decreased throughout. Invertase activityremained constant for about four days of forcing, then increasedand later decreased.