We analyzed DNA damage, mitotic activity and polyploidization in Crepis capillaris callus cells during short- and long-term in vitro culture, and the influence of plant growth regulators on these processes. Changes in the concentration of growth regulators altered the stability of callus. The level of DNA damage was highly dependent on the growth regulator composition of the medium. Cytokinin at high concentrations damaged DNA in the absence of auxin. Short- and long-term callus differed in sensitivity to growth regulators. Mitotic activity changed when callus was transferred to medium with modified growth regulators. Callus cell nuclear DNA content increased with age and in response to plant growth regulators. Hormones played a role in the genetic changes in C. capillaris callus culture. We demonstrated the usefulness of C. capillaris callus culture as a model for analyzing the effect of culture conditions, including plant growth regulators, on genetic stability.

Trinexapac-ethyl is one of the newest growth regulators used in agriculture and horticulture. As a most growth retardants it acts by inhibiting gibberellin (GA) biosynthesis. A field study was conducted to determine the effects of trinexapac-ethyl on growth of winter wheat. Trinexapac ethyl was used alone (75 g a.i./ha and 125 g a.i./ha) and in the mixture with chlorocholine chloride (50 g a.i./ha + 675 g a.i./ha) at the 2nd node stage. Trinexapac-ethyl and its mixture with CCC activity was weather dependent. Their influence on the crop was strictly related to the temperature and rainfall during an individual year of trials. Plant growth regulators much more influenced winter wheat plants in abundant rainfall and higher temperature conditions. Lodging was not observed during the experiment.

The influence of adjuvants on the efficacy of the plant growth regulators: chlormequat chloride (CCC) and prohexadione-calcium was investigated in winter wheat in 2002 and 2003. Field trials were carried out in the Agricultural Experimental Farm in Winna Góra. The plant growth regulators were applied alone at normal rate and at a r educed rate with and without adjuvants. Two adjuvants were used: Adpros 85 SL, a methylated rapeseed oil and Break-Thru S-240, an organosilicone surfactant. Crop height, lodging, yield and quality of the harvested crop were assessed. Physicochemical properties of spray solution were measured. Adjuvants improved the biological activity of both, CCC and prohexadione-calcium, especially when reduced doses were applied. Efficacy of the plant growth regulators used at normal rate without adjuvant and at reduced rates with adjuvants was similar. Break-Thru S-240 increased the efficacy of CCC and prohexadione-calcium more compared to Adpros 85 SL measured in terms of reduction of plant heigh.

Rare and endemic plant species represent important components of plant biodiversity which require protection to ensure their sustainable conservation. Cerastium banaticum (Rochel) Heuff. is such an endemic and rare species from Romania, for which the genetic variability of two natural populations was studied by SSR markers. Shannon’s information index revealed low levels of genetic diversity in both populations (I = 0.296). As the first attempt in a conservation program a reproducible micropropagation protocol was established starting from seeds, followed by multiplication, rooting, and ex vitro acclimatization. Among the various plant growth regulators tested the highest multiplication coefficient was achieved on a culture medium with 0.5 mg L-1 6-furfurylaminopurine (K) and 1 mg L-1 α-naphthaleneacetic acid (NAA). On this PGRs concentration a number of 26.6 shoots/individual explant with a mean length of 7.9 cm for new generated shoots was registered. The highest number of roots/individual initiated shoot was 2.6 and it was recorded on a culture medium with 0.5 mg L-1 2-isopentyl-adenine (2iP) and 0.1 mg L-1 NAA. The outdoor acclimatization was successfully performed in a specially designed rocky area in the ‘Alexandru Borza’ Botanical Garden, Cluj-Napoca (Romania).

The genus Narcissus has several endemic, rare and/or threatened species in the Iberian Peninsula and North Africa. In vitro propagation is a useful tool for threatened plants conservation used in ex situ strategies. Thus, the aim of this work was to study the propagation in vitro of bulb scale explants of five endemic, rare and/or endangered Narcissus species from the Iberian Peninsula, treated with different PGR combinations. Initiation was achieved in half-strength Murashige and Skoog (MS) basal salts and vitamins, 10 g/L sucrose, 500 mg/L casein hydrolysate, 2 mg/L adenine, 10 mg/L glutathione and 5.5 g/L plant agar. In the multiplication phase, the highest bulblet proliferation was obtained in MS medium supplemented with 30 g/L sucrose and the combination of 10 μM 6-Benzylaminopurine (BAP) + 5 μM α-Naphthaleneacetic acid (NAA) in N. alcaracensis, N. eugeniae and N. hedraeanthus; 20 μM BAP + 5 μM NAA in N. jonquilla and N. yepesii. The highest rooting was obtained with 5 μM NAA + 1 μM Indole-3-butyric acid (IBA) for all species (>75%) and more than 80% of the produced bulblets were successfully acclimatized.