Plant biostimulants are of interest as they can stimulate plant growth and increase resource utilization. There is still no information on the use of plant growth-promoters under variable nutritional conditions in the nursery and the effects on tomato seedling growth and plant performance after transplant. This study aimed to evaluate the suitability of gibberellic acid (GA3) or bacterial biostimulant treatments to enhance the growth and quality of greenhouse-grown tomato (Solanum lycopersicum ‘Marmande’) seedlings, fertigated with increasing nutrient rates and to assess the efficacy of these treatments on the early growth of tomato plants. During autumn 2019, tomato seedlings were inoculated with 1.5 g L−1 of TNC BactorrS13 (a commercial biostimulant containing 1.3 × 108 CFU g−1 of Bacillus spp.) or sprayed with 10−5 M GA3 and fertigated with a nutrient solution containing 0, 1, 2 and 4 g L−1 of NPK fertilizer (20-20-20) when they reached the 11th BBCH growth stage for tomato. Subsequently, the seedlings were evaluated in greenhouse cultivation for 60 days until at least the 61st BBCH growth stage (January 2020). The growth of the tomato seedlings increased curvilinearly in relation to the fertigation rates. The GA3-treated seedlings showed similar or even higher growth parameters than the control seedlings fed with 4 g L−1 of fertilizer but with half of the nutrients. The inoculation of the substrate with Bacillus spp. had negative effects in the absence of fertigation but determined a greater growth at the highest fertigation rate. The bacterial inoculum of seedlings had longer-term effects than the GA3 treatment during the plant growth, but these effects were noticeable mainly when the bacterial biostimulant was associated with the highest fertigation rate.
International audienceThe degree of tolerance to the sulfonylurea herbicide rimsulfuron (R) was investigated in four F$_6$ pepper lines: Argo (Ar), Heldor (He), Ideal (Id) and Indalo (In), by evaluating the activity and kinetic parameters of the target site they contain, acetolactate synthase (ALS), as well as herbicide persistence. After 48 hours from treatment the herbicide was completely metabolised in He, Id and In, while Ar had a 0.4 ppm residue. As shown by I$_{50}$ values, ALS sensitivity to R proved to be different in the four lines according to the following increasing order: In, He, Id and Ar. Enzyme kinetic studies revealed a distinct expression of natural ALS endowment in all lines. In particular, V$_{{\rm max}}$ in the untreated samples was greatest in He followed by, in decreasing order, Id, Ar and In. Compared to untreated samples V$_{{\rm max}}$ values were greater in treated In and lower in the other treated as follows He $< $ Id $< $ Ar. K$_{\rm m}$ values were lower in In and He than in Ar and Id, and were unaffected by R treatment. The present study indicates that In and He are more tolerant to R than Ar and Id, given their lower ALS sensitivity to R together with their higher enzyme activity, which is naturally occurring in He and R-induced in In. Moreover, a greater R persistence resulted in Ar than in the other lines. These findings were confirmed by a field trial which showed growth damage and a reduction of productivity in the Id and Ar lines.Facteurs de tolérance au rimsulfuron dans quatre lignées de poivron (Capsicum annum L.). On a étudié le degré de tolérance à l'herbicide sulfonyluré rimsulfuron (R) dans quatre lignées de poivrons F$_6$ : Argo (Ar), Heldor (He), Ideal (Id) et Indalo (In), en évaluant l'activité et les paramètres cinétiques du site-cible qu'ils contiennent - acétolactate synthase (ALS) - ainsi que la persistance de l'herbicide. Quarante huit heures après le traitement, l'herbicide avait subi une métabolisation complète dans He, Id et In, tandis que Ar présentait un résidu de 0,4 ppm. Comme l'ont montré les valeurs I$_{50}$, les quatre lignées ont témoigné d'une sensibilité différente de ALS à R, dans l'ordre croissant suivant : In, He, Id et Ar. Les études sur la cinétique des enzymes ont révélé que la dotation naturelle en ALS s'exprime différemment dans toutes les lignées. Notamment, dans les échantillons non traités, la V$_{{\rm max}}$ la plus élevée était celle de He, suivie, par ordre décroissant, de Id, Ar et In. Par rapport aux échantillons non traités, on a relevé des valeurs de V$_{{\rm max}}$ plus élevées dans In traité et plus basses dans les autres lignées traitées avec décréments dans l'ordre : He $< $ Id $< $ Ar. Les valeurs K$_{\rm m}$ étaient plus basses dans In et He que dans Ar et Id et n'ont pas été touchées par le traitement au R. Ces données indiquent que In et He ont une tolérance plus élevée à R que Ar et Id, grâce à une sensibilité moindre d'ALS à l'égard de R ainsi qu'à leur activité enzymatique plus élevée, naturelle dans He et provoquée par ...
The shortage of good quantity and quality of water for irrigated agriculture is a major problem in arid and semiarid regions. To deal with this problem, deficit irrigation (DI) or arbuscular mycorrhizal fungi (AMF) inoculation have been proposed and adopted for many crops as a tool to save water, or to improve crop tolerance to drought stress. An experiment was conducted for two consecutive years to evaluate the effect of mycorrhizal inoculation on the physiological, morphological, yield, and quality characteristics of melon plants grown under deficit irrigation. Melon crop (Cucumis melo L. cv. Helios) was grown under field conditions adopting a split-plot design with four replications, where DI was the main factor and AMF inoculation was the secondary factor. DI treatments consisted of applying 60%, 80%, or 100% of crop evapotranspiration (ETc) on melon plants inoculated or not with a commercial biostimulant containing 50% of Rhizophagus irregularis, and 50% of Funneliformis mosseae. Moderate and severe deficit irrigation significantly reduced the relative water content, stomatal conductance, yield, nitrogen applied efficiency (NAE), and fruit firmness of the uninoculated plants, but significantly increased irrigation water use efficiency (IWUE) and the ascorbic acid content of the fruit. AMF had a positive effect on plant tolerance to moderate water stress, and on some fruit quality parameters (fruit length, firmness, and sugar content). The combined use of moderate deficit irrigation (80%) and soil inoculation with AMF on melon plants allows water savings without affecting fruit yield, and increases IWUE, NAE, and some fruit quality characteristics (firmness, SSC, and SSC/TA). Furthermore, the use of AMF plants could be worth it to reduce the yield loss and increase fruit quality, even with severe deficit irrigation (60%).
Ecklonia maxima and the commercial biostimulants produced from it contain various plant growth regulators that are responsible for the growth stimulation recorded in many crops. Auxins are one of the major plant growth regulators contained in E. maxima extracts. The aim of this research was to evaluate the growth-promoting effect of a seaweed extract from E. maxima on lettuce and tomato transplant production under nursery conditions, and to compare the effect of this extract with an equal concentration of synthetic auxin. Two doses of natural or synthetic exogenous auxins (50 or 100 μg L−1) were supplied to the substrate through the irrigation water with an ebb and flow system, 4, 11, and 18 days after sowing. A commercial biostimulant based on E. maxima extract was used as a source of natural auxin, while 1-naphthaleneacetic acid (NAA) was used as a synthetic auxin. Seedlings supplied only with water were used as a control. Tomato seedlings treated with 100 μg L−1 of natural auxins from E. maxima extract produced the tallest plants (+22%), with a higher leaf number (+12%), a wider leaf area (+44%), and a stronger stem (+12%), whereas lettuce seedling growth was promoted by all the treatments, but with a greater effect with increasing auxin supplementation and when using E. maxima extract, compared to NAA. The results showed that the supplementation of exogenous synthetic auxin (NAA), or an E. maxima extract containing natural auxins, can have a growth-promoting effect on lettuce and tomato seedlings. This effect was more evident on lettuce than tomato. The biostimulant produced from E. maxima extracts improved seedling quality and promoted shoot and root growth more than the NAA used as a synthetic source of auxins.
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