Abstraet. Accumulation of nitrogen (N) by plants in response to N supply outstripping demand is contrasted with storage of N, which itnplies that N in one tissue can be reused for the growth or maintenance of another. Storage can, therefore, occur in N-deficient plants; accutnulation can not. The consequence of accumulation and storage of N is considered, particularly in relation to the reproductive growth of annual plants, which can often use a great deal of stored N. Nitrate and proteins are the fonns of N most often stored in vegetative tissues and, quantitatively, ribulose 1,5bisphosphate carboxylase/oxygenase is often the most important protein store. While storing nitrate will be less costly to the plant in terms of energy, protein stores offer several possible advantages. These advantages are (i) maximizing the potential for carbon assimilation, (ii) avoiding problems with the regulation of leaf turgor and (iii) allowing the reduction on nitrate to occur in the young, fully illuminated leaf.

The accumulation and storage of nitrogen by herbaceous plants

Increased incidence of sulphur (S) deficiency in crops has led to a greater need for S determination in plant tissues. Among the methods available for measurement of S, inductively coupled plasma atomic emission spectrometry (ICP‐AES) has been proved to be accurate and rapid. This paper compares digestion with HNO3‐HClO4, fuming HNO3‐KNO3 and alkaline NaOBr prior to the S measurement by ICP‐AES. Both HNO3‐HClO4 and fuming HNO3‐KNO3 were found to give satisfactory results for five certified plant materials, with high accuracy and precision. The HNO3‐HClO4 method involved a rigid temperature control, with slow ramp rates and a final temperature (190°C) lower than the boiling point of HClO4, to minimise the possibility of gaseous losses of S. Both methods can also be used for the simultaneous determination of phosphorus (P), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn), and additionally potassium (K) with HNO3‐HClO4. In contrast, the alkaline NaOBr method was l...

Comparison of three wet digestion methods for the determination of plant sulphur by inductively coupled plasma atomic emission spectroscopy (ICP‐AES)

Root architecture differences have been linked to the survival of plants on phosphate (P)-deficient soils, as well as to the improved yields of P-efficient crop cultivars. To understand how these differences arise, we have studied the root architectures of P-deficient Arabidopsis (Arabidopsis thaliana Columbia-0) plants. A striking aspect of the root architecture of these plants is that their primary root elongation is inhibited when grown on P-deficient medium. Here, we present evidence suggesting that this inhibition is a result of iron (Fe) toxicity. When the Fe concentration in P-deficient medium is reduced, we observe elongation of the primary root without an increase in P availability or a corresponding change in the expression of P deficiency-regulated genes. Recovery of the primary root elongation is associated with larger plant weights, improved ability to take up P from the medium, and increased tissue P content. This suggests that manipulating Fe availability to a plant could be a valuable strategy for improving a plant's ability to tolerate P deficiency.

The Effect of Iron on the Primary Root Elongation of Arabidopsis during Phosphate Deficiency

Interaction among plant nutrients can yield antagonistic or synergistic outcomes that influence nutrient use efficiency. To provide insight on this phenomenon, peer-reviewed articles were selected ...

https://www.tandfonline.com/doi/pdf/10.1080/00103624.2017.1407429

Effects of Nutrient Antagonism and Synergism on Yield and Fertilizer Use Efficiency

A cellular hypothesis for the induction of blossom-end rot in tomato fruit

Active Iron in Plant Leaves

The effect of sulphur fertilisation on yield and herbage composition was investigated in two successive years at two grassland sites, one with ryegrass and one with ryegrass/ clover, where the available sulphur in the soil was less than 10 mg kg−1. When supplies of N, P and K were not limiting, herbage yields increased with added sulphur at both sites, particularly at the second and third cuts and in the second year. Sulphur additions also increased the concentrations of total S and SO4−2−S in the crop, and reduced the N:S ratio. The figures for these parameters in herbage from control plots confirmed that low yields in the presence of normal nitrogen fertilisation were probably caused by sulphur deficiency.

Response of grassland to the application of sulphur at two sites in north‐east scotland

Blossom-end rot (BER) of tomatoes has been studied in a glasshouse using varieties both prone and resistant to the disorder. The plants were grown in modules of peat with different amendments of lime and fertiliser and in a commercial peat mix containing magnesium ammonium phosphate as a slow release fertiliser (‘Enmag’). Nutrient solutions containing nitrogen as the ammonium ion, the nitrate ion, urea or ammonium nitrate were added daily. The incidence of BER was high with the ammonium nitrogen and was aggravated by ‘Enmag ’With nitrate nitrogen, incidence of BER was much reduced or negligible, whereas with urea or ammonium nitrate, the incidence was intermediate. Higher levels of calcium reduced the disorder. Chemical analyses of the blossom-end of affected and healthy tomatoes showed that in BER tissues both calcium and iron were reduced whereas the potassium and phosphorus contents and the potassium-malate ratios were increased.

Blossom-end rot in tomatoes

A study of the growth of oats in peat of very low copper content has been made. It was found that various nutrient amendments improved growth but the effect of copper was overriding. There was some evidence for copper unavailability due to fixation by organic matter, but it appears that the known interactions between major and minor elements largely determined the appearance and severity of copper deficiency.

Factors affecting the copper content of oats grown in peat

The effects of water stress, ammonium sulphate, sodium nitrate and ammonium nitrate on the incidence of blossom-end rot (BER) in tomatoes was studied, using plants grown in peat modules. There was little evidence that water stress per se affected BER incidence, which was largely determined by the ammonium ion, as found in previous studies. Water stress increased ammonium and nitrate levels in both the peat modules and the leaves of the plants. This effect may account for the relation between moisture stress and BER reported by others.

R. H. E. Inkson

Papers

Active Iron in Plant Leaves

Response of grassland to the application of sulphur at two sites in north‐east scotland

Blossom-end rot in tomatoes

Factors affecting the copper content of oats grown in peat

The effect of water stress and form of nitrogen on the incidence of blossom-end rot in tomatoes