Biochemical studies on blossom end rot of tomatoes

The causes of cell wall necrosis in Blossom End Rot (BER) of tomatoes have been investigated by comparing enzyme activities in healthy and affected tissues in the cultivars Grenadier and Moneymaker. Changes in the mineral contents of the tomatoes were in accordance with those of calcium deficient tissues. The phenolic contents of the affected tissues were increased as also were caffeic and chlorogenic acids. Phenolase and peroxidase activities were higher in affected fruits white catalase activities were higher in healthy fruits. ¹⁴C-labelled leucine was incorporated into the proteins of the healthy fruits to the greatest extent but cell wall proteinbound hydroxyproline was greatest in affected fruits.     

Effects of Hydroxyproline and other Amino Acid Analogues on the Growth of Pea Root Segments

Changes in the lengths and growth rates of isolated 2–4 mm pea root segments, cultured in sucrose media under aseptic conditions, were paralleled by changes in invertase development and in chloride and leucine uptakes. The amino acid analogues o-, m- and p-fluorophenylalanine, azetidine-2-carboxylic acid and ethionine inhibited growth with corresponding changes in invertase activity and in chloride and leucine uptakes. In contrast hydroxyproline, which under the conditions used may be regarded as an analogue of proline, enhanced both the growth rate and duration of growth but had little effect on the several parameters of protein synthesis which were measured. No amino acid tested affected changes in growth, invertase activity or the uptake of chloride and leucine, but they prevented the effects of the corresponding analogues. The results show that although extension growth is dependent on continuous protein synthesis, only specific proteins, probably in the cell wall, play a key role in this process.     

The Effect of Salicylic Acid on the Growth of Lemna gibba

Salicylic acid added as the iron chelate causes extension ofthe pedicels and distortion in the growth of daughter frondsof Lemna gibba, when included in a nutrient salt medium whichcontains the ammonium ion. The effect is abolished if iron orcopper is omitted from the nutrient solution or if the mediumcontains only nitrate nitrogen. The effect is specific for salicylicacid or acetyl salicylic acid; substituted or analogous compoundsare without effect.     

The Fine Structure of Leaf Cells of Copper-deficient Oats

Electron micrographs of copper-deficient oat leaves showed onlyminor structural differences from normal oat leaves in thatthere were reduced numbers of compartments in the chloroplaststacks with no differences in stromacentres, plastoglobuli,mitochondria, nuclei, or cell walls. The cells of the whitewithered tip characteristic of copper-deficient oat leaves werefound to be full of fibrous masses.     

A Study of Peroxidase and Catalase Distribution in the Potato Tuber

The activities of peroxidase and catalase were determined inconsecutive segments from cores struck from heel to rose endsof potato tubers, cv. Majestic, which had been grown in plotsof soil having nominal pH values of 4.5, 5.0, 5.5, 6.0, 6.5,7.0 and 7.5. Gradients of activity were computed and shown tobe parabolic upwards for peroxidase and parabolic downwardsfor catalase at the higher soil pH levels but both tended toshow linear trends in the more acid soils. The ratios of theactivities of peroxidase to catalase were at a maximum betweenpH 5.5 and 6.0 and decreased towards either end of the pH range. Solanum tuberosum, potato, tuber, enzyme activity, peroxidase, catalase     

The Leaf Tip of Ranunculus reptans L.

The knob-like structure at the leaf tip of Ranunculus reptansis shown to have glandular c aracteristics, probably actingas a hydathode. Specialized cells with pyrenoid-like bodiesoccur round the hydathode apertures.     

Heavy Metal Toxicity and Iron Chlorosis

1. The toxicity of copper, nickel, cobalt, zinc, chromium, andmanganese to mustard was studied in water culture, utilizingeither the ionic form or the EDTA chelate of the metal in thepresence of either ferric chloride or ferric EDTA. 2. In presence of ferric chloride the activity of the metalsin producing chlorosis was as given above, i.e. in the orderof stability of their chelates. In the presence of ferric versenate,toxicity of the ionic metal was much reduced. The metal chelatesgave very little indication of toxicity with either form ofiron. 3. It was found that the ratio of total phosphorus to totaliron was higher in chlorotic plants than in green plants, irrespectiveof which metal was causing the toxicity. 4. Copper could be demonstrated in the phloem cells of the rootusing bis-cyclohexanone-oxalydihydrazone as histochemical reagent.It is postulated that transport of iron probably takes placein the phloem as an active process. 5. It would appear that as a major part of the iron in plantcells is attached to nucleo- or phospho-proteins, the heavymetals must be similarly attached to phospho-proteins.     

Nutrient Distribution in the Potato Tuber in Relation to Soil pH

Potato tubers grown in experimental plots maintained at nominalpH values ranging from 4.5 to 7.5 were sampled by striking coresections from heel to rose ends. These were divided into consecutivepieces and analyzed for cations and anions and also the traceelements iron, manganese and copper. Linear regression equationswere fitted to each set of data thus giving the gradient ofeach constituent from heel to rose ends of the tubers. The gradientof each constituent within the tuber could then be comparedin relation to soil pH. Only the calcium content of the tuberincreased markedly with increased pH but the ratios of potassiumplus sodium to calcium plus magnesium and of phosphorus to ironboth showed maxima at pH 6 and decreased towards either endof the pH range. Solanum tuberosum, potato, tuber, calcium availability, soil pH