Untitled

Funder

Organizational Unit

Publications

Allelopathic effects of extracts from several plant species on seed germination and seedlings growth of Lactuca sativa L

Publication . Gonçalves, Sandra; Franco, J.; Romano, Anabela

The ability of a plant species to inhibit germination of other plants is an untapped resource for weed control in crops that could revolutionize organic crop production. The main objective of this study was to evaluate the allelopathic potential of aqueous (5 and 10%, w/v) and methanolic (50mg ml-1) extracts from several plant species (Arbustus unedo L., Ericaceae; Daphne gnidium L., Thymeleaceae; Myrtus communis L., Myrtaceae; Olea europea L., Oleaceae; Pistacia lentiscus L., Anacardiacceae; Quercus suber L., Fagaceae; Ruscus aculeatus L., Liliaceae, Rhododendron ponticum subsp baeticum (Boissier & Reuter) Handel-Mazzetti, Ericaceae) on seed germination and seedling growth of Lactuca sativa. To test the phytotoxicity 500µl of the extract were added separately over filter papers (9cm diameter) in Petri dishes. It was observed that methanolic extracts from M. communis and R. aculeatus completely inhibited seed germination, and almost all the extracts tested reduced seed germination and/or seedling growth. The inhibition of root growth was generally higher than of shoot growth, with the highest percentages of root inhibition being observed with the aqueous extracts of D. gnidium (80 and 72% for the extract at 5 and 10%, respectively) and R. aculeatus (74 and 78%), and with the methanolic extract of Q. suber (74%). Besides inhibiting seedling growth other morphological abnormalities occurred in the presence of the extracts. Roots of treated plants were thicker with a brownish color as compared to controls. Studies are being conducted to investigate the phytotoxic effect of the extracts on physiological and biochemical processes during germination and seedlings growth.

2008Journal article

Open Access

Insecticidal activity of leaf extracts from Drosophyllum lusitanicum against Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)

Publication . Gonçalves, Sandra; Gonçalves, Maria; Ameixa, Olga; Nogueira, José Manuel F.; Romano, Anabela

The present study was carried out to evaluate the insecticidal properties of Drosophyllum lusitanicum (L.) Link, an insectivorous plant that is endemic to the western Iberian Peninsula and northwest Morocco. The insecticidal capacities of extracts from field-grown D. lusitanicum plants were evaluated using contact and feeding bioassays against female adults of Liriomyza trifolii (Burgess), one of the major pests of several floricultural and vegetable crops. In addition, the toxicity of the extract from in vitro cultures of D. lusitanicum was evaluated in contact bioassays. The results showed that extracts of D. lusitanicum have considerable insecticidal potential, particularly through contact application (100% mortality 1 d after treatment). Moreover, extracts from in vitro cultures had similar toxicity to those from field-grown plants. Extracts were analysed by gas chromatography coupled to mass spectrometry (GC-MS). The major constituent was 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin), and its level was similar in extracts from field-grown plants (11.0 mg ml–1) and from in vitro cultures (8.2 mg ml–1). Although the results suggest that the insecticidal activity of extracts of D. lusitanicum is probably due to the presence of this naphthoquinone, further detailed research is required to identify other compounds that may be responsible for the activity.

2008Journal article

Restricted

How to monitor the acclimatization of micropropagated plants - From in vitro to the field?

Publication . Osório, Maria Leonor; Gonçalves, Sandra; Coelho, N.; Romano, Anabela; Osório, Júlio

The high mortality experienced by plants during ex vitro transplantation stage is the major bottleneck in large scale application of micropropagation. The abnormal physiological and anatomical characteristics of micropropagated plantlets require that they should be gradually acclimatized to the environment of the greenhouse or field. Environmental factors, especially relative humidity and irradiance, play a critical role in both physiological and biochemical functions, namely water relations, gas exchange, photosynthetic efficiency and water oxidation, during transition from in vitro to ex vitro conditions. Throughout this period of transition and acclimatization substantial changes in those characteristics are necessary to achieve a successful micropropagation. This adaptation should be accurately monitored using relevant physiological parameters including pigment content, chlorophyll a fluorescence imaging, net photosynthetic rate, transpiration rate, and stomatal conductance. Growth traits and oxidative stress markers, such as electrolyte leakage, lipid peroxidation and hydrogen peroxide content, should be also analyzed. These parameters must be assessed during the course of ex vitro acclimatization in several periods and compared with those of plants growing in their natural habitat. The performance plants of Tuberaria major, an endangered species endemic from the Algarve region (Portugal), during their acclimatization through indoor-to-outdoor conditions was monitored using several physiological and biochemical traits as indicators. In view of the results, we concluded that the transplantation protocol described can be used for restoration purposes, contributing to the preservation of the species. © ISHS 2013.

2013Journal article

Restricted