Lettuce seeds belonging to four different varieties, for a total of fifteen lots, were used as a model to highlight and analyze thermo- and photo-dormancy problems in lettuce. The seeds were subjected to a priming treatment (ISIJet), dried to the initial weight and sown in Petri dishes. To obtain a comparison of data, untreated seeds and seeds treated with ISIJet were plated at the same time. The plates, each containing one hundred seeds, were placed in light and dark conditions at different temperatures. Specifically, the germinability of lettuce seeds was analyzed at four and seven days at different temperatures (20-25-30-35°C). Having thus obtained the germination percentages in the different light and temperature conditions, a statistical analysis was carried out to look for significant differences between the lots analyzed and to have a first practical demonstration of the thermo- and photo-dormancy phenomena. The analysis highlighted a major problem of germination especially at extreme temperatures (35°C). With the data obtained, it was decided to focus the analysis only on over-optimal temperatures (30-35°C), significant temperatures in which the thermodormancy phenomenon is most observed. Therefore, four lots of the fifteen available were used, one for each variety, and priming protocols were developed with the aim of alleviating dormancy and uniform germination even in non-optimal growth conditions. Lettuce seeds, belonging to the four selected batches, were plated and placed in different light and temperature conditions as done previously in the first part of the experiment. Nine priming treatments were tested which differ both in the solutions used and in the concentrations of the solutions and in the temperature conditions to which the seed was subjected during the treatment. For these lots, the germination analysis was carried out approximately every twenty-four hours, up to day four and finally to day seven. This was mainly used to monitor the progress of seed germination in the first few days, to verify the contribution of the treatment to lettuce seeds. This was followed by the statistical analysis of the germination results obtained which showed that some of the treatments analyzed significantly improve growth performance compared to the others, especially in the first few days. However, there is a clear difference in the germinability trend at 30°C compared to 35°C where the seeds have more problems in germinating even if they have been treated. In conclusion, there is still a lot to do to better understand the phenomenon of dormancy in crops and especially in lettuce and this is a big problem that seed companies must face. The aim of the latter is precisely to offer a reliable and quality product even in non-optimal growth conditions and these pre-sowing treatments are increasingly used because they can increase and standardize the germinability of the seed even in adverse conditions.
Semi di lattuga appartenenti a quattro varietà differenti, per un totale di quindici lotti, sono stati utilizzati come modello per evidenziare e analizzare i problemi di termo- e foto-dormienza in lattuga. I semi sono stati sottoposti a un trattamento di priming (ISIJet), essiccati fino ad ottenere il peso iniziale e seminati in piastre Petri. Per ottenere un confronto di dati sono stati piastrati contemporaneamente semi non trattati e semi trattati con ISIJet. Le piastre, contenenti ognuna cento semi, sono state collocate in condizioni di luce e buio a differenti temperature. Nello specifico, è stata analizzata la germinabilità dei semi di lattuga a quattro e sette giorni a temperature differenti (20-25-30-35°C). Ottenute così le percentuali di germinazione nelle diverse condizioni di luce e temperatura, si è proceduto a effettuare un’analisi statistica per cercare delle differenze significative tra i lotti analizzati e avere una prima dimostrazione pratica dei fenomeni di termo- e foto-dormienza. Dall’analisi si è evidenziato un grande problema di germinabilità soprattutto a temperature estreme (35°C). Coi dati ottenuti si è deciso di focalizzare l’analisi solo su temperature sovra ottimali (30-35°C), temperature significative in cui si osserva maggiormente il fenomeno della termodormienza. Quindi, sono stati utilizzati quattro lotti dei quindici a disposizione, uno per ogni varietà, e sono stati sviluppati dei protocolli di priming con l’obbiettivo di alleviare la dormienza e uniformare la germinabilità anche in condizioni di crescita non ottimali. Semi di lattuga, appartenenti ai quattro lotti selezionati, sono stati piastrati e posti nelle diverse condizioni di luce e temperatura come fatto precedentemente nella prima parte dell’esperimento. In tutto sono stati testati nove trattamenti di priming che differiscono sia per le soluzioni utilizzate che per le concentrazioni delle soluzioni e per le condizioni di temperatura a cui il seme è stato sottoposto durante il trattamento. Per questi lotti l’analisi della germinabilità è stata svolta ogni ventiquattro ore circa, fino al giorno quattro e infine al giorno sette. Questo è servito soprattutto per monitorare l’andamento della germinabilità del seme nei primi giorni così da verificare l’apporto del trattamento ai semi di lattuga. È seguita l’analisi statistica dei risultati di germinabilità ottenuti che hanno mostrato come alcuni dei trattamenti presi in analisi abbiano miglioramento significativamente le performance di crescita rispetto agli altri soprattutto nei primi giorni. È netta la differenza, tuttavia, di andamento delle germinabilità a 30°C rispetto a 35°C dove i semi presentano più problemi a germinare pur essendo stati trattati. Concludendo, c’è ancora tanto da fare per comprendere al meglio il fenomeno della dormienza nelle colture e soprattutto in lattuga e questo è un grande problema che le ditte sementiere devono affrontare. Obbiettivo di quest’ultime è appunto quello di proporre un prodotto affidabile e di qualità anche in condizioni non ottimali di crescita e questi trattamenti di presemina sono sempre più utilizzati perché in grado di aumentare e uniformare la germinabilità del seme anche in condizioni avverse.
TERMO- E FOTO-DORMIENZA IN LATTUGA E SVILUPPO DI PROTOCOLLI DI PRIMING PER AUMENTARE E UNIFORMARE LA GERMINABILITÀ
FURIOSI, LORENZO
2020/2021
Abstract
Lettuce seeds belonging to four different varieties, for a total of fifteen lots, were used as a model to highlight and analyze thermo- and photo-dormancy problems in lettuce. The seeds were subjected to a priming treatment (ISIJet), dried to the initial weight and sown in Petri dishes. To obtain a comparison of data, untreated seeds and seeds treated with ISIJet were plated at the same time. The plates, each containing one hundred seeds, were placed in light and dark conditions at different temperatures. Specifically, the germinability of lettuce seeds was analyzed at four and seven days at different temperatures (20-25-30-35°C). Having thus obtained the germination percentages in the different light and temperature conditions, a statistical analysis was carried out to look for significant differences between the lots analyzed and to have a first practical demonstration of the thermo- and photo-dormancy phenomena. The analysis highlighted a major problem of germination especially at extreme temperatures (35°C). With the data obtained, it was decided to focus the analysis only on over-optimal temperatures (30-35°C), significant temperatures in which the thermodormancy phenomenon is most observed. Therefore, four lots of the fifteen available were used, one for each variety, and priming protocols were developed with the aim of alleviating dormancy and uniform germination even in non-optimal growth conditions. Lettuce seeds, belonging to the four selected batches, were plated and placed in different light and temperature conditions as done previously in the first part of the experiment. Nine priming treatments were tested which differ both in the solutions used and in the concentrations of the solutions and in the temperature conditions to which the seed was subjected during the treatment. For these lots, the germination analysis was carried out approximately every twenty-four hours, up to day four and finally to day seven. This was mainly used to monitor the progress of seed germination in the first few days, to verify the contribution of the treatment to lettuce seeds. This was followed by the statistical analysis of the germination results obtained which showed that some of the treatments analyzed significantly improve growth performance compared to the others, especially in the first few days. However, there is a clear difference in the germinability trend at 30°C compared to 35°C where the seeds have more problems in germinating even if they have been treated. In conclusion, there is still a lot to do to better understand the phenomenon of dormancy in crops and especially in lettuce and this is a big problem that seed companies must face. The aim of the latter is precisely to offer a reliable and quality product even in non-optimal growth conditions and these pre-sowing treatments are increasingly used because they can increase and standardize the germinability of the seed even in adverse conditions.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/14195