A storage role for albumins in pea cotyledons

Abstract It is widely held that the albumins of pea seeds are mainly enzyme proteins. In the present study of Pisum sativum cv. Greenfeast, certain major polypeptides confined to the albumin fraction from the cotyledons were shown to be degraded in vivo following germination, thus functioning as a reserve of amino nitrogen and carbon skeletons. A general definition of seed storage proteins is proposed, to encompass any protein present in major quantity in the seed which is degraded following imbibition, and for which no other function may be demonstrated.     

The cytology of the genus Alopecurus (Gramineae)

For a study of hybridization in Alopecurus , chromosome numbers, karyotypes, meiotic chromosome behaviour and breeding systems have been investigated in six species. In addition to confirming many previous chromosome numbers, new triploid and tetraploid counts have been found in A. bulbosus , which have not previously been reported. The karyotypes of all species have a very similar morphology but there are differences in chromosome size which can be related to differences in nuclear DNA content. At meiosis the diploid species form bivalents, but one population of A. aequalis contains plants that regularly form a single quadrivalent which would appear to be interchange heterozygotes. The meiotic behaviour of the tetraploids suggests that A. pratensis is an allotetraploid and A. geniculatus an autotetraploid. All species appear to be allogamous, although some, such as A. myosuroides are obligate outbreeders resulting from the presence of a self-incompatibility system, outbreeding is promoted in others by differences in the time of maturity of stigmas and anthers.     

Unstable B chromosomes in Silene maritima With. (Caryophyllaceae)

Unstable B chromosomes in Silene maritima With. (Carophyllaceae). B chromosomes have been found in 7 out of 39 populations of Silene maritima With. (Carophyllaceae) studied. These 7 populations are all from the Norfolk coast. The B chromosome is small, 0.8 μm long, telocentric and appears euchromatic. Within plants the B chromosome is highly unstable with different numbers in cells of the same root or pollen mother cells (pmcs) of an anther. The transmission of the Bs is efficient and in controlled crosses progeny plants usually have higher mean B frequencies than the B-containing parents. At metaphase I the pairing behaviour of the Bs is variable and they often appear as univalents. In general the presence of Bs in pmcs results in an increase in chiasma frequency/cell and populations with Bs have higher mean chiasma frequencies than those without Bs. Cloned plants grown under stress conditions induced by the addition of NaCl to a nutrient solution showed no difference in mean B number/cell or distribution when compared with controls grown in nutrient solution only.     

Modelling adult survival in the laboratory of diapause and non-diapause Colorado beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) from Normandy, France

Adult Leptinotarsa decemlineata from a culture originally from Normandy, France were kept in a controlled environment and fed daily on potato foliage. Dead beetles were scored and removed. Setting up the experiment was spread over 212 days and 1135 beetles were used. After 21 days each group was divided into two, some remained active and others were induced to diapause for 221 days before becoming active once again. Life span varied from 1 to 504 days and could be extended to 770 days by diapause. A model was derived which describes the mortality over time by assuming that a proportion of the population had an exponential distribution of lifetime and the remainder had a Weibull distribution which allowed for a hazard rate increasing with time. In the model 17% were short-lived, having a mean lifetime of 8 days, and the remainder were long-lived having a mean lifetime of 139.5 days. An exponential survivor function describes the post-diapause cohort, which had a mean lifetime of 129 days after diapause.