Para-nitrophenyl Phosphate as a Substrate for Some Acid Phosphatases in Roots of Vicia faba

A cytochemical and biochemical study of acid phosphatases inroots of Vicia faba using p-nitrophenylphosphate(p-NPP) as substratehas shown the lack of specificity of the substrate which canbe acted upon by a K⁺-activated acyl phosphatase, nucleotidepyrophosphatase, glucox-6-phosphatase, 5' (3')-ribonucleotidephosphohydrolase, nucleotide phosph-transferase and those acidphosphatases demonstrable with ß-glycerophosphate.It is suggested that care should be taken in the interpretationof both biochemical and cytochemical studies employing sucha non-specific substrate as P-NPP. Vicia faba, broad bean, root, acid phosphatases     

An Autoradiographic Study of Bacterial DNA in Lycopersicon esculentum

³H-DNA from Escherichia coli has been fed to cut shoots of Lycopersiconesculentum. Autoradiographic studies have shown the bacterialDNA to be localized in the nuclei, plastids, and mitochondriaof cells in the phloem, cambium, parenchyma, collenchyma, andepidermis. Two populations of cells were detectable, namely, those withnuclei in which the ³H-DNA was localized, and those which failedto incorporate ³H-DNA into their nuclei. This may, in part,be due to the degree of availability of the DNA in these tissues,cambium, parenchyma, and collenchyma.     

The Quiescent Centre and Cell Determination in Roots of Pisum sativum

A combined autoradiographic and enzyme cytochemical study ofroot apices from Pisum sativum has permitted the demonstrationof a high naphthol AS-D esterase activity in the central groupof meristematic cells immediately outside the quiescent centre.This high naphthol AS-D esterase activity indicates an expressionof the programming of these cells to form elements of the stele.A consideration is given to the need for a quantal mitosis andof its possible occurrence in the quiescent centre. It is concludedthat the programming and mitotic activity may be two physiologicalevents which whilst occurring in the same cell, are not necessarilylinked events. Pisum sativum, roots, determination, quiescent centre, autoradiography, carboxylesterases     

Histochemical Study of Photoperiodic and Low Temperature Effects on Floral Induction of Spinacia oleracea

Shoot apices of Spinacia oleracea plants have been induced toflower either by: (a) subjecting leaves to 24 h long day, or(b) exposure to a short photoperiod but displaced by 8 h (displacedshort day) in the usual 24 h short-day cycle, or (c) exposureto low temperature (5 °C) during the dark period of thenormal short day. A quantitative cytochemical assay of pentosephosphate pathway activity during floral induction indicatesan approximate doubling of the rate of activity when comparedto that of vegetative apices (short day) (21 °C). Exposure to either low temperature, or a displaced short photoperiodstimulates pentose phosphate pathway activity in the shoot apexin a manner similar to that seen by long-day induction. Thischange in metabolic activity is accompanied by changes in theshape of the shoot apex which resembles that seen at an earlystage during floral induction. Spinacia oleracea, pentose phosphate pathway, shoot apex, glucose-6-phosphate dehydrogenase, floral induction, chilling, displaced short day     

Stimulated and Non-stimulated Rat Spleen Cells Release Different DNA-Complexes

Isolated rat spleen cells released into the culture medium a complex containing newly-synthesized DNA. Upward sucrose density gradient centrifugation yielded material from non-stimulated cells at a major peak of density 1.03, with minor peaks at 1.04 and 1.055. However, the complex from cells stimulated with phytohaemagglutinin showed a major peak at 1.052, with little material at 1.03. The low densities indicated that the complexes contained a high proportion of lipid, confirmed by the incorporation of ³H-ethanolamine. Data indicate that newly synthesized DNA leaves the nucleus, crosses the cytoplasm, and associates with the cell membrane prior to leaving the cell as a complex with the DNA protected against nuclease activity.     

Increased Pentose Phosphate Pathway Activity Linked to Floral Induction in Apices of Spinacia oleracea during Short Days

A quantitative cytochemical study of glucose-6-phosphate dehydrogenaseactivity as a marker of the pentose phosphate pathway (PPP)was made on shoot apices of Spinacia oleracea kept either continuouslyin short days for up to eight weeks or transferred for a singleperiod of 20 h to continuous light after between three and eightweeks in short days. By the time the apices kept in continuousshort days showed morphological changes relating to the floralstate, the PPP activity was already elevated. From four weeksonwards, the apices were more readily induced to the floralstate as evidenced by the increased PPP activity. In addition,the level of PPP activity achieved in the short-day apices asthey progressed to the floral state was as great as that observedin the apices induced to flower by a 20-h day. Spinacea oleracea, pentose phosphate pathway, shoot apex, cytochemistry, glucose-6-phosphate dehydrogenase, floral induction     

Histochemical localisation of carboxylesterases in roots of Lycopersicon esculentum in response to Meloidogyne incognita infection

A cytochemical study of esterase activity of tomato cultivars resistant (VFN8) and susceptible (Roma) to the root-knot nematode Meloidogyne incognita has shown activity present in root tissue of both cultivars. Inhibitor studies indicated the likely involvement of carboxy- and acetyl-esterases as components in the prostele and cortical cells of cv. Roma 1, 2, and 3 days after nematode infestation. In contrast, necrotic cells immediately adjacent to the nematode in roots of VFN8 were seen to contain high levels of phenolics by 3 days after infection with the adjacent cells having high levels of carboxylesterase activity. The possible role of the enzyme in the hypersensitive response of tomato plants during nematode infection is discussed.     

Microsatellites isolated from diamondback moth,Plutella xylostella (L.), for studies of dispersal in Australian populations

Diamondback moth, Plutella xylostella (L.), is a worldwide agricultural pest that has developed resistance to many insecticides used for its control. Population structure and gene flow are yet to be determined for P. xylostella in Australia, but are important factors for the design of effective control strategies. We have isolated six polymorphic microsatellite markers: three from a partial genomic library, two from an Expressed Sequence Tagged library and one from an aminopeptidase intron of P. xylostella. These microsatellites will be used to determine population structure and gene flow in Australian populations of P. xylostella to improve insecticide resistance management.     

Turnover of DNA in Ageing Tissues of Lycopersicon esculentum

Cut shoots of Lycopersicon esculentum were placed in [³H]thymidine(d[³H]Thd) for 24 h and then re-rooted. Immediately after theisotope pulse a variety of tissues in the lower internode regionwere found to have incorporated label into nuclear DNA. Duringthe prolonged chase period it was discovered that the amountof labelled DNA declined significantly in all tissues. Reasonsfor the apparent turnover or degradation of the labelled DNAare discussed for each tissue.