The Effect of Temperature Change on Leakage from Pea Seeds

Intact seeds of P. sativum and P. elatius leaked electrolytes,sugars and proteins for as long as 48 h after the beginningof imbibition. Initial leakage was higher at 25 °C thanat 5 °C, but its extent was much greater at the lower temperature.Transfer of seed from 5 °C to 25 °C after 5 h imbibitionresulted in leakage for 48 h at the initial rate at 5 °C.The transfer from 25 °C to 5 °C gave leakage at a rateequivalent to the initial rate at 25 °C. The results arediscussed in relation to behaviour of membranes and to the sensingof the initial temperature. Key words: Pisum sativum, P. elatius, Leakage, Electrolytes, Sugars, Proteins, Temperature     

Germination, Utilization of Storage Materials and Potential for Cyanide Release in Cultivated and Wild Sorghum

Sorghum halepense germinates only after storage and its germination is impeded by its glumes. On germination its metabolism is more rapid than is S. bicolor, as indicated by loss of dry weight, starch and protein and formation of soluble protein and soluble sugars. Fresh weight formation is also more rapid in S. halepense. A method for determining the potential for cyanide liberation is described. S. halepense builds up the potential rapidly and apparently maintains it after germination. This process is also slower in S. bicolor. The results show that the cultivated species is slower in all the processes leading to germination than the wild one.     

Respiration and Utilization of Storage Materials in Wild and Cultivated Pea Seeds during Germination

Breakdown of storage materials, oxygen uptake, respiratory control and ADP/O ratios in the cotyledons of the garden pea P. sativum and in the wild pea P. elatius were compared. Starch and protein degradation was slower in P. elatius than in P. sativum. Embryo growth began later in the wild pea. However, in the garden pea the mitochondria were uncoupled after about 48 h of germination, while in P. elatius the ability to carry out oxidative phosphorylation was maintained for 4 days. The respiratory control ratio was higher in the wild pea at all stages of germination and a steady level of oxygen uptake was maintained in the cotyledons for at least 3 days. The findings are discussed in relation to the ecological requirements for germination in the two species.     

Relation Between the Anatomy of the Testa, Water Permeability and the Presence of Phenolics in the Genus Pisum

The seed coats of Pisum elatius, P. fulvum and P. humile areimpermeable to water while those of P. sativum and P. humilex P. sativum are permeable. The anatomical structure of theseed coats and the location of phenolics and quinones in thecells is described. The barriers to permeation of water in theimpermeable seeds are the continuous, very hard, pectinaceouslayer of the caps of the palisade cells and the presence ofquinones in either the palisade or osteosclereid cells, in acontinuous layer of these cells. In water permeable seeds thecaps are looser and quinones discontinuous or absent in palisadeor osteosclereid cells. Pisum, testa, water permeability, quinones, phenolics, palisade cells, osteosclereids, pectinaceous caps     

Formation of Catechol Oxidase in Seed Coats of Pisum elatius during Seed Maturation

The catechol oxidase present in the seed coat of Pisum elatiusat various stages of seed maturation was partially characterized.The pH dependence and response to inhibitors and stimulatorsof the enzyme was determined. Inhibitors of protein synthesisand enzyme activity were introduced into the developing seedsvia the pod. During the early stages of seed maturation, theincreased enzyme activity was probably due to de novo synthesiswhile the increase in the later stages of maturation can bestbe accounted for on the basis of activation of pre-existingenzyme, perhaps due to conformational changes in the enzyme.The evidence for this view is discussed.