Browsing by Subject "day length"

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  • Toivonen, Tiina (Helsingfors universitet, 2014)
    Timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) are generally grown forage grasses at high latitudes. Growing of perennial ryegrass (Lolium perenne L.) and xFestulolium hybrid is possibly increasing in the future. The climate change will alter autumn growth conditions in Finland. The aim of this study was to investigate differences in autumn growth and accumulation of reserve carbohydrates between forage grass species and cultivars from different geographical origin. The objective was also to study autumn growth ability after third cut, cold tolerance, tiller density and content of soluble sugars in chosen cultivars in field conditions during winter. This study was carried out at growth chamber experiment and field trial. There were four different autumn growth conditions in growth chambers: first 5 °C/14 h and 10 °C/14 h and secondly 15 °C/12 h and 15 °C/14 h. Vegetative factors like ligule height and activity of photosynthesis and concentration of soluble sugars were measured from timothy, meadow fescue, perennial ryegrass and xFestulolium lines. Autumn growth yield after third cut, cold tolerance (LT50) and reserve carbohydrates of perennial ryegrass and xFestulolium cultivars during winter were measured in field trial (Nov. & Jan./Feb.). According to this study low temperatures (5 and 10 °C) prevented formation of lateral tillers effectively in timothy but not in other species because they formed new lateral tillers and accumulated biomass. Low temperatures (5 and 10 °C) prevented height growth in all studied lines and long day length (14 h) allowed height growth only in higher temperature (15 °C). Perennial ryegrasses and xFestulolium cultivars grew similarly in short (12 h) and long (14h) day length but the growth of timothy was delayed in short day length. Southern timothy breeding line grew significantly height in the 15 °C and 14 h growth conditions whereas northern timothy breeding line formed more lateral tillers. The photosynthesis activity of all tested genotypes was high in all growth conditions and concentration of soluble sugars increased in low temperatures but not in high temperatures except in northern timothy. According to the field trial the overwintering of perennial ryegrasses and xFestulolium cultivars was challenging especially in second winter and the decline of low temperature tolerance was connected to vernalization saturation of xFestulolium cultivars during winter. There was strong variation in autumn growth between years.
  • Tujula, Anna (Helsingfors universitet, 2009)
    Suomen tärkein viljelty marja on mansikka, jonka tuotannon eräänä ongelmana on satokauden lyhyys. Eräänä ratkaisuna tähän saattaisivat olla jatkuvasatoiset mansikkalajikkeet, joita ei Suomessa ole laajassa viljelyssä lähinnä sopivien lajikkeiden puutteen vuoksi. Mansikalla vegetatiivinen ja generatiivinen kasvu kilpailevat osittain keskenään. Jatkuvasatoisilla mansikkalajikkeilla generatiivista kehitystä ja sadon muodostumista edistää pitkä päivänpituus. Satopotentiaalia voidaan lisätä myös kemiallisilla kasvun- sääteillä. Proheksadioni-kalsium (ProCa) toimii gibberelliini-inhibiittorina edistäen juurakon haaroittumista ja siten kukkimista sekä ehkäisten rönsyjen muodostumista. Satopotentiaalia lisää myös lyhyt päivänpituus edistämällä kasvin koon kasvua. Tehdyssä tutkimuksessa testattiin kolmen jatkuvasatoisen mansikkalajikkeen (Elan, Malling Pearl ja Tango) reagointia sekä lyhyeen (12 h) että pitkään päivään (18 h) ja ProCa:an (0 ja 200 ppm). Käsittelyt suoritettiin taimikasvatuksen aikana, minkä jälkeen kasvit siirrettiin hyötöön muovitunneliin. Kasvien vegetatiivista ja generatiivista kehitystä havainnoitiin sekä taimikasvatuksen että hyödön aikana useiden vasteiden, kuten lehtien, rönsyjen, juurakon haarojen, kukintojen ja marjojen määrien, avulla. Käsittelyillä oli vaikutusta sekä vegetatiiviseen että generatiiviseen kehitykseen, mutta erot koejäsenten välillä tasoittuivat melko nopeasti. Pitkä päivä nosti Elanin ja Malling Pearl:n kukkien määrää, mutta vain ProCa:lla käsitellyillä koejäsenillä. Tangolla kukkia sen sijaan kehittyi vain lyhyenpäivän koejäseniin, se käyttäytyi meidän oloissamme siis täysin lyhyenpäivänlajikkeen tavoin. Myös ProCa lisäsi kukintojen määrää, mutta lajikkeiden välillä esiintyi vaihtelua vaikutuksen voimakkuudessa. Sekä pitkä päivä että ProCa nostivat Elanin ja Malling Pearl:n satotasoa varsinkin alkukesästä, eli sadontuotto aikaistui. ProCa nosti myös Tangolla sekä aikaisen että kokonaissadon määrää. Tutkimus osoitti mahdollisuuden mansikan sadon aikaistamiseen ja sen määrän nostoon jatkuvasatoisten lajikkeiden avulla, jos niiden potentiaalia pystyttäisiin täysin hyödyntämään. Lisätutkimusta tarvitaan kuitenkin edelleen sopivien lajikkeiden ja viljelytekniikoiden kehittämiseksi.Strawberry is the most important cultivated berry in Finland but one of the problems of cultivation is shortness of the harvesting period. Everbearing strawberry cultivars could provide an alternative to extend the period. However, these are not yet broadly cultivated in Finland mainly due to the lack of suitable cultivars. The vegetative and generative growth of strawberry partly compete with each other. Generative growth and yield formation in everbearing strawberries is enhanced by long day length. Yield potential can also be increased by using chemical growth regulators, like prohexadione-calcium (ProCa). This inhibitor of gibberellin biosynthesis enhances crown branching and flowering, and prevents runner formation. Yield potential can also be thought to increase by short day length through increasing plant size. In this study, the effect of short (12 h) and long (18 h) day length as well as ProCa (0 and 200 ppm) on the growth of three everbearing strawberry cultivars (Elan, Malling Pearl and Tango) were tested. The treatments were carried out during plant propagation after which the plants were moved to a plastic tunnel for forcing. Vegetative and generative development of the plants were observed during both plant propagation and forcing by measuring several variables, such as number of leaves, runners, crown branches, flowers and berries. The treatments affected both vegetative and generative development. Long day increased the number of flowers on Elan and Malling Pearl, but only on ProCa treated plants. Flowering of Tango on the other hand was only induced in the short day length. Thus, in our conditions, it behaved as a short day cultivar. ProCa also increased the number of flowers, but there were some differences between the cultivars in the strength of the effect. Both long day length and ProCa increased the yield of Elan and Malling Pearl especially in the early summer, thus advancing the start of fruiting. ProCa also increased both early and total yield of Tango. This study showed the possibility of advancing and increasing strawberry yield through everbearing cultivars if their potential could be fully utilised. Further research is however necessary in order to develop suitable cultivars and cultivation methods for our growing conditions.