Willows produce fast germinating and short-lived seeds, difficult to store in the long-term under controlled conditions. The aim of this study was to examine the feasibility of storage of three Salix spp. at controlled temperatures (3°, −10°, −196 °C). We also analyzed the effect of spermidine (Spd) as an antioxidant factor in desiccated seeds. Collected seeds were either desiccated or hydrated to obtain 10 levels of moisture content (between app. 4% and 2%) and subjected to storage at temperatures 3°, −10°, or −196 °C (liquid nitrogen; LN). After two months, seeds were germinated on the light at 20 °C. Seeds desiccated below a safe range of moisture content were further tested and germinated on filter paper with additions of 0.25 mM Spd solution. After 7 days seedlings were examined for hydrogen peroxide content (H2O2) and total antioxidant capacity (TAC). Fresh seeds of three Salix species: Persian willow (S. aegyptiaca L.), heartleaf willow (S. cordata Michx.) and crack willow (S. ×fragilis L.) were successfully stored at temperature −10° and −196 °C for two months. After cryopreservation seed of S. aegyptiaca, S. cordata, and S. ×fragilis germinated without viability loss in moisture content ranging from 4.4–15.9%, 6.4–18.5%, and 7.1–11.5% respectively. The addition of Spd during germination of desiccated seed did not affect germination capacity. However, seedlings of S. aegyptiaca had lower hydrogen peroxide content in comparison with control (germination on water). Seedlings of S. cordata showed an increase in hydrogen peroxide content in control after storing in LN. In seedlings of Crack willow Spd increased hydrogen peroxide content. Seeds of tested species differ in response to storage conditions. Salix seeds can be stored successfully for two months at −10° or −196 °C without losing viability in the safe range of moisture content. Storing at 3 °C can be used for storage in the narrower range of seeds’ moisture content, however, seedlings stored at this temperature produce a higher level of reactive oxygen species. Germinating seeds in Spd did not increase their germination, however in S. aegyptiaca and S. cordata decreased hydrogen peroxide content
Individual moisture content of acorns of English oak (Quercus robur L.) paired with germination, seedling emergence and seedling growth (mass, height and root collar diameter).
The conservation of the genetic resources of old trees is crucial to their ecological role but is extremely difficult, especially for oak species (Quercus spp.) displaying recalcitrance in seed and vegetative propagation methods. Our study aimed to assess the regenerative potential of Quercus robur trees of different ages (up to 800 years) during micropropagation. We also aimed to determine how in vitro conditions can influence in vitro regeneration responses. Lignified branches collected from 67 selected trees were cultivated ex vitro in culture pots at 25 °C to obtain epicormic shoots (explant sources). The explants were cultivated on an agar medium supplemented with 0.8 mg L-1 6-benzylaminopurine (BAP) for at least 21 months. In a second experiment, two different shoot multiplication conditions (temporary immersion-RITA® bioreactor and agar medium) and two culture medium formulations (Woody Plant Medium and modified Quoirin and Lepoivre medium) were tested. The results showed that the mean length of the epicormic shoots obtained in a pot culture was a function of donor age and was similar among the group of younger trees (ca. 20-200 years), and varied between older trees (ca. 300-800 years). The efficiency of in vitro shoot multiplication strictly depended on the genotype. A sustainable in vitro culture (defined as survival after 6 months) was only possible for half of the tested old donor trees, even when they survived the first month of in vitro growth. A continuous monthly increase in the number of in vitro cultured shoots was reported in younger oaks and in some old oaks. We found a significant effect of the culture system and the macro- and micronutrient composition on in vitro shoot growth. This is the first report demonstrating that the in vitro culture can be successfully applied to the propagation of even 800-year-old pedunculate oak trees.
ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Advances in Ornamentals, Landscape and Urban Horticulture SOMATIC EMBRYOGENESIS AND CRYOPRESERVATION OF ORNAMENTAL PICEA SPECIES: MODERN METHODS OF PROPAGATION AND LONG-TERM STORAGE
Nine seedlots of the widely planted southern and central European native tree species Acer pseudoplatanus L. were collected along a north–south gradient spanning 21° of latitude in Europe. We investigated how the heat sum during seed development influences seed maturity as assessed by physical, physiological and biochemical traits. Using principal component analysis we found predictable and consistent patterns in all traits, which correlated with heat sum. For example, compared with fruits from their native range (Italy and France, heat sum >3000°C d), fruits from the coldest location (Scotland; heat sum of 1873°C d) were shorter (c. 30 v. 42 mm), germinated over a narrower temperature range (5–20 v. 5–35°C) and had smaller embryos (28 v. > 70 mg) with a higher water content (c. 63 v. 48%), less negative solute potentials (c. –2.4 v. –4.1 MPa) and were more desiccation sensitive (critical water potential of –20.2 v. –55.4 to –60.7 MPa). The observed level of desiccation-tolerance for the French and Italian seedlots is more consistent with the intermediate category than the previous classification of A. pseudoplatanus as recalcitrant. Our results demonstrate that a lower heat sum causes fruits from northern Europe to be dispersed before maximum potential seed quality is achieved.
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