Philippe Morard

Bicarbonate‐pH relationship with iron chlorosis in white lupine

Abstract The effect of different pH levels (4.5, 5.5, 6.5, and 7.5) on the growth and mineral nutrition of white lupine (Lupinus albus L., cv. Alban) was investigated in nutrient solution. At pH 7.5, i.e. at the highest bicarhonate concentration, the growth of the roots and of the aerial parts of lupine was decreased significantly. Growth impairment was accounted for in terms of two processes: i) in spite of the presence of Fe‐EDDHA iron chelate in the pH 7.5 solution, white lupine displayed symptoms of iron chlorosis, which were associated with a significant deccase in total and ferrous‐Fe contents in the younger leaves where the major cation content was increased; and in white lupine, the total and ferrous‐Fe contents are therefore good indicators of the iron nutrition level, and ii) the decrease in nodulation, in nitrate uptake from the nutrient solution, and in nitrogen content in the younger leaves reflects the decreased nitrogen nutrition of white lupine. These results suggest that chlorosis is like...

Effect of oxygen deficiency on uptake of water and mineral nutrients by tomato plants in soilless culture

Abstract The consequences of oxygen deficiency on the root system of tomato plants in soilless culture at the beginning of the flowering stage were assessed over a 72‐hour period. The study of water uptake and oxygen depletion in the medium was conducted using a process of continuous computerized data processing. Fluctuations in composition of the nutrient solution were monitored every two hours through an analysis of samples. Oxygen deficiency of the nutrient solution had immediate effects on the water and nutrient uptake of the whole plant. The root asphyxia of a tomato plant caused a 20 to 30% decrease of water uptake after 48 hours. After 10 hours it also leads to the end of the uptake process of the nutrients except nitrates. Potassium (K) was the nutrient most sensitive to oxygen deprivation since an efflux into the culture medium was observed after only 4 hours of deprivation. Nitrate uptake was the least affected by oxygen deficiency. The persistent appearance of nitrite in the culture medium 12 hours after the beginning of the asphyxia process could be caused by the reduction of nitrates by the root system of the tomato plant. The plant would use the oxygen from the reduction reaction to ensure the water and nitrate uptake processes which are the two most important limiting factors of plant nutrition. Thus it seems that under root asphyxia conditions the plant would adapt to the new condition by relying on a metabolism of the “nitrate respiration”; type.

Alkalinity-bicarbonate-calcium effects on iron chlorosis in white lupine in soilless culture

White lupine is a calcifuge plant that is susceptible to iron chlorosis. To gain insight into the iron stress mechanisms involved in calcareous soils, the effects of calcium and bicarbonate concentrations and pH were investigated separately on hydroponically grown lupines. Iron was supplied as Fe-EDDHA.

Optimization of the mineral composition of in vitro culture media

Abstract Plant tissue culture requires the optimization of growth media. The effect of eight different macronutrient formulations on the in vitro culture of Gatharanthus roseus nodes was investigated: the caulogenesis rate decreased with the overall ion concentration and the ammonium content of the growth medium. The methodology proposed for the optimization of the mineral composition of the growth medium is based upon the adjustment of the macronutrients contents to the plant requirements. Such an approach was used for the comparison between the effects of the optimized growth medium and those of the usual Murashige and Skoog solution in the growth of the multiple shoots issued from Solatium paludosum root calluses. The new formulation MH1 [with a diminution of the ionic concentration, nitrogen (N) supplied in the form of nitrate and calcium (Ca) in larger amounts than potassium (K)] doubled the biomass production and tripled the yield of solamargine, a secondary metabolite.

Effect of temporary calcium deficiency on tomato growth and mineral nutrition

Abstract The effects of temporary calcium deficiency on the growth and mineral nutrition of whole tomato (Lycopersicon esculentum All. cv. Rondello) plants were investigated at the 22–23 leaf stage. Three deficiency period durations (5, 8, and 10 days or ‐Ca5, ‐Ca8, and ‐Ca10, respectively) were tested during the two series of hydroponic experiments in a greenhouse. At the end of the calcium deficiency period, the plants were supplied again with a standard nutrient solution. In the plants subjected to a 5‐day calcium deficiency, stem growth and new leaf formation were slowed 10–12 days after the onset of the treatment. The effect was rapidly attenuated and no visual symptom was observed thereafter. The stem growth slow‐down induced by treatments ‐Ca8 and ‐Ca10 8–10 days after the onset of calcium deficiency was followed by the rapid appearance of visual symptoms and by the death of the apical meristem. Thus, beyond five days, even though the plant was supplied again with calcium, the appearance of visual ...

DIRECT EFFECTS OF HUMIC-LIKE SUBSTANCE ON GROWTH, WATER, AND MINERAL NUTRITION OF VARIOUS SPECIES

The influence of humic-like substances was studied on various crop plants (cucumber, maize, pelargonium, and wheat, for example) cultivated under hydroponic conditions. The humic-like product, called SHB®, was extracted from poplar sawdust by a thermical and mechanical process and applied diluted into nutrient solutions of soilless culture at concentrations ranging between 100 to 400 mg SHB® L−1. The application of the humic-like substance induced a biostimulating effect on plant growth of each species studied. Treated plants present a faster development and reach reproductive stage three to five days earlier than control. SHB® also provoked a better efficiency of plant water uptake and they improved the mineral nutrition. It is assumed that most of direct effects on plant metabolisms are related to the low molecular size fractions (LMS) because it is the only part of SHB® which can penetrate into root tissues. But, it is also suggested that high molecular size fractions (HMS) could participate in plant water saving by slowing down its passage in roots.

Kinetics of mineral nutrient uptake by Saponaria officinalis L. suspension cell cultures in different media

Abstract The uptake of mineral nutrients from two media with different mineral composition, a classical MSA medium and a modified MH2 medium, by Saponaria officinalis (soapwort) cells was studied over a growth cycle of 14 days, by continuous measurement of mineral consumption without opening the culture flasks. The mineral composition of the MH2 medium was found to be better suited to S. officinalis cells. Culture on MSA medium showed that copper is probably a factor limiting growth, that phosphate is rapidly exhausted from this medium, that its strong ammonium concentration is antagonistic to the absorption of potassium and, lastly, that sodium and chlorine may be considered as non-essential elements.

Effect of Oxygen Deficiency on Mineral Nutrition of Excised Tomato Roots

Abstract The influence of oxygen deficiency on uptake of water and mineral elements through root system was studied on detopped tomato plants for 48 h. The root exudates and the nutrient solutions were collected and analyzed every two hours after decapitation of the shoots at the early fruiting stage. The lack of oxygen in the nutrient solution induced the appearance of nitrite ions in the nutrient medium and in the xylem sap. Nitrites were derived from nitrate reduction by tomato root cells. This mechanism, called “nitrate respiration”, should be an alternative pathway to have oxygen as electron acceptor during root anoxia and could be a transient adaptation to hypoxic conditions. The lack of oxygen in the nutrient medium caused a 42% reduction of water consumption by excised tomato roots during the experiment. The deprivation of oxygen induced also an efflux of potassium, magnesium, phosphate and sulfate in the nutrient solution. So, this experimentation allows to obtain information about macronutrient uptake mechanisms by excised tomato roots. The uptake of potassium, magnesium, phosphate and sulfate is an “active process”, directly linked to the energetic catabolism. On the opposite, the absorption of calcium is a “passive process”, in the pathway of the electrochemical gradient via the water xylem flow.

Blade or petiole analysis as a guide for grape nutrition

Abstract The leaf opposite the first fruit cluster was used for the investigation of grape nutrition at bloomtime and ripening. The data show that blade analysis and petiole analysis are both suitable for the assessment of the nutrient status in the case of P, K, Mg and Ca. However, the data obtained for nitrogen differ markedly, depending on the organ considered. For phosphorus and potassium, the differences in nutrient content between vineyards as well as the seasonal variations are better reflected by petiole analysis. This effect, which should be favourable to the diagnosis, is paralleled by a wider scattering of the nutrient levels; as a result, the differences observed in the petiole are not statistically more significant than those in the blade. Under relatively homogeneous conditions (same variety, same climate), the differences induced by variable parameters (soil type, sampling times, years) appear to be fluctuating, so that nutrient reference levels cannot be recommended, whether for the blade ...

Selectivity of the root absorption of nutrient ions in grain sorghum

Abstract Root absorption selectivity, which refers to the fact that the mineral elements are not found in the same proportions in the plant as in the growth medium, was characterized using plots where the proportions between the elements were considered. Grain sorghum was grown hydroponically in nutrient solutions where the cationic macroelements were increasingly replaced with sodium and the anionic macronutrients with chloride. The data obtained from the analyses of the nutrient solutions and of the whole plants show that root selectivity promotes the absorption of K+ and NO3 ‐ ‐N and impedes that of Ca++ whereas there is nearly no selectivity towards the other nutrients (Mg, P, S).The high negative selectivity towards unessential elements (Na and Cl) is reflected by their very low proportions within the plant. The comparison between the various plant organs shows that the proportions of the essential elements are nearly identical in the roots, the sheaths, the younger leaves and in the adult leaves (on...