Effects of ageing on peroxidase activity and localization in radish (Raphanus sativus L.) seeds.

Peroxidase activity was assayed in crude extracts of integument, cotyledons and embryo axis of radish seeds, deteriorated under accelerated ageing conditions. Over five days of ageing, in which germination decreased from 100 to 52%, the enzyme activity in integument was higher than that in other seed parts, increasing in the first days of ageing and then decreasing sharply in extremely aged seeds. Polyacrylamide gel electrophoresis analysis showed four peroxidase isoenzymes with MM of 98, 52.5, 32.8 and 29.5 kDa in the embryo axis of unaged seeds, and only the 32.8 and 29.5 kDa MM isoforms in the integument and cotyledons. In these parts of the seed, only the 29.5 kDa MM isoenzyme increased in activity in early days of ageing and decreased there-after. In the embryo axis, the 29.5 kDa MM isoenzyme activity increased slowly in the first day of ageing, while the 98 and 52.5 kDa MM isoenzyme activities disappeared. A cytochemical localization of peroxidase activity in the various tissues showed that main differences between unaged and extremely aged seeds occurred in the embryo axis.

Structural and histochemical changes during seed development of Brassica macrocarpa Guss.

During seed formation of Brassica macrocarpa the development of the embryo precedes that of the integuments; structural changes and histochemical changes are associated. Esterases, acid phosphatases, phenols and starch follow a sigmoid pattern, increasing during embryogenesis and decreasing during seed maturation. In the mature seed, esterase activity is localized in the embryo and in the cells of the mucilaginous, aleuronic and hyaline layers. Acid phosphatases are present in the mucilaginous cells, mainly in the column, the cell walls delimiting intercellular spaces of the cortical cylinder and the adhesion areas of the cotyledons. Phenols are scanty in the root apex, mucilaginous cells and the palisade layer, and abundant in the pigmented layer. Starch is absent in ripe seeds which have lipid and protein reserves. The major classes of storage proteins have molecular weights of 21, 22, 27 and 30 KD and accumulate in the late stages prior to complete drying. Esterases and acid phosphatases in mucilaginous cells of the seed integument suggest that these enzymes are involved in hydrolytic processes occurring prior to germination and that mucilages have a metabolic function in seed-soil interactions.

Effects of simulated acid rain on pollen physiology and ultrastructure in the apple.

Viability, germination and tube length were investigated in pollen grains of field-grown 'Summerred' apple trees (Malus domestica Borkh) exposed to deionized water, rainfall or simulated acid rain at pH 5.6, 4.0 and 3.0. Pollen viability and germination significantly decreased with lower values of pH and with increasing number of treatments. The effects of pH 5.6 and natural rainfall were not significant. Electron microscope investigation of vegetative pollen cells of plants exposed to acid rain at pH 4.0 and 3.0 showed modified features in mitochondria, plastids and endoplasmic reticulum.

Differential staining for cellulosic and modified plant cell walls.

A simple method to enhance the staining of cell wall components for fluorescence microscopy is described. In stems of Nicotiana tabacum and needles of Pinus eldarica lignin, the cuticle and unsaturated lipids are indicated by a purple-red fluorescence while pectocellulosic components fluoresce pale blue.

The in-vitro response of pollen germination and tube length to different types of acidity.

Pollen germination and tube growth are among the most sensitive responses to atmospheric pollution. Both these are inhibited by the acidity of the growth medium. Pollen grains from two species (Pinus cembra L. and Sambucus nigra L.) were germinated in media over a range of pHs (5.0, 4.5, 4.0, 3.5, 3.0 and 2.5) and six types of acidity (H(2)SO(4), HNO(3), H(2)SO(4): HNO(3) in 1:1, 2:1, 3:1 and 5:1 ratio). Pollen of the Gymnosperm is shown to be more resistant to acidity in the medium. Sulphuric acid alone and the ratio 2:1 with nitric acid are demonstrated to be the more harmful for P. cembra and S. nigra, respectively. The latter species was sensitive to all mixtures, particularly in respect to germination percentage.

A quantitative cytochemical method for phosphofructokinase in plant tissues.

A quantitative cytochemical method for the demonstration of phosphofructokinase has been successfully applied to a range of plant tissues. The findings indicate that this enzyme system may be assayed as an indicator of glycolytic activity in plant cells, and furthermore tha the very high endogenous phosphoenolpyruvate concentrations may not be rate limiting in vivo.