Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 72

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 4 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  frost resistance
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 4 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The concrete with compact structure on the basis of Portland cement modified by the dispersion of multilayer carbon nanotubes GraphistrengthTM by Arkema is investigated. The change in the structure of cement stone in the process of concrete setting and hardening when introducing carbon nanotubes into the concrete composition is observed.
Seedlings of hybrid forms of winter triticale and of their parents were hardened against frost and their frost resistance was determined. Three groups of cultivars were separated with respect to their frost resistance: 1) Low resistant: Salvo and Bolero, 2) Intermediate: Almo, Ugo and LAD 490, 3) High resistant: Tewo, Bogo, Tornado, Nemo and Vero. Heterosis in relation to frost resistance was not significant when the hybrid forms were compared with a better parent, but it appeared while comparing the frost resistance of some hybrid forms with mean values of that of parents.
In the years 2000-2010, observations were made of shrubs of the varieties derived from the Pimpinellifolia (R. pimpinellifolia L.) gathered in the Collection of Rose Culti- vars of PAS Botanical Garden in Powsin, Poland. The nine observed varieties were 'Aïcha', 'Elegans', 'Frühlingsduft', 'Frühlingsgold', 'Frühlingsmorgen', 'Harison's Yel­low', 'Maigold', 'Poppius', and 'Stanwell Perpetual'. Every year, the following were recorded: frost damage; the date of bud breaking and the date when leaves developed in springtime; the date of the initial, complete and final flowering; the presence of symptoms of damage from disease and pests; the ability to create decorative fruit, and remarks concerning the necessity to perform spring cutting and cutting after flower­ing. The winter seasons of 2002/2003, 2005/2006 and 2009/2010 were unfavourable for the roses. The cultivars varied greatly according to the examined features. The advantages of many of the varieties include high frost resistance, early flowering, low requirements in terms of cutting, good condition; and the fact that some varieties create suckers ('Elegans', 'Harison's Yellow', 'Poppius', 'Stanwell Perpetual'). The varieties 'Aïcha', 'Elegans', 'Frühlingsduft', 'Frühlingsgold', 'Poppius', 'Stanwell Perpetual' are the most frost resistant. The least frost-resistant variety is 'Maigold'. The first to flower are 'Harison's Yellow', 'Frühlingsmorgen' and 'Poppius'. Varie­ties derived from Rosa pimpinellifolia can be widely used as park roses, as ground covers, and as soil protective roses ('Elegans', 'Harison's Yellow', 'Poppius', 'Stan­well Perpetual').
The presented studies have shown the effect of soil fatigue on the decrease of resistance to low temperatures in one-year old apple-tree shoots. The highest frost resistance was demonstrated by the shoots of apple-trees grown in localities so far not utilized for fruit-tree cultivation.In a replanted apple-tree orchard, the plantation of trees in the grass inter-rows of the old apple orchard did not cause any explicit increase of frost resistance by the apple-tree shoots.
The article presents the results of observations in the years from 1998-2002/2003 concerning the adaptation of some plants that come from warmer climatic regions to the weather conditions that are found in Szczecin. A list of species and varieties of trees and shrubs among which no frost damages were observed is presented in table 1.
Studies on the effects of temperature during the early stage of growth on frost resistance of winter rape seedlings under controlled conditions were performed. It was found that cold acclimation responses of plants were affected to a great extent by the conditions of the seedlings early growth. During this period, when the day temperatures were reduced to the range from +10 °C to +15 °C, a process termed “prehardening” was observed. During prehardening plants formed leaf rosettes. Their ability to develop frost resistance during acclimation at +2 °C also increased. Frost resistance of these plants was comparable with the resistance of plants growing in autumn under field conditions.
Experiments performed under controlled conditions showed that level of PPFD (photosynthetic photon flux density) during early seedlings growth (preceding cold acclimation at +2 °C) was not the key factor for the development of frost resistance. It did not modify the beneficial effects of prehardening (Rapacz 1997, in this issue) at moderately low (+12 °C) day temperature. Now I have shown that the increase of PPFD may replace to some extent prehardening in the development of frost resistance. It was particularly seen in non-prehardened plants, which had been grown under warm-day (+20 °C) conditions. Prehardening performed under controlled conditions, as well as seedlings growth under natural autumn conditions in the field, allowed to maintain a high net-photosynthesis rate at chilling temperatures. A net-photosynthesis rate during cold acclimation at +2 °C corresponded well with higher frost resistance. As a result, seedlings non subjected to prehardening and grown before cold acclimation under low PPFD acclimated better, if the cold treatment was applied only at nights (+20/2 °C day/night). Only under such conditions the photosynthetic rate was sufficiently high to allow plants to reach a higher level of frost resistance. All other plants acclimated better when they were exposed to the hardening temperature continuously during days and nights (+2/2 °C day/night).
Mechanizmy adaptacyjne pozwalające zbożom ozimym przeżyć niskie temperatury są zaprogramowane genetycznie i kontrolowane przez liczne geny indukowane i regulowane przez niską temperaturę. W niniejszym przeglądzie opisano ostatnie osiągnięcia dotyczące funkcji genów indukowanych przez niską temperaturę i ich roli w mrozoodporności. Zaprezentowane tutaj wyniki pozwolą zrozumieć mechanizmy wykształcone przez rośliny w toku ewolucji, pomagające przeżyć mróz. W dodatku odkrycia te mają potencjalny aspekt praktyczny w selekcji i hodowli odmian zbóż ozimych odpornych na niekorzystne warunki zimowania.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 4 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.