Akumulacja kwasu abscysynowego a poziom uszkodzeń w warunkach chłodu u 20 linii wsobnych kukurydzy

The role of ABA in chilling tolerance (CT) of maize seedling has been reinvestigated using a set of new maize inbred lines with defined differences in CT. Under chilling conditions (4°C) the ABA level increased in all lines investigated. This increase was significantly higher in the chilling tolerant lines than in sensitive ones. Between ABA level and extent of chilling injury a significant relationship was observed. ABA level correlated negatively with percent necrotic injury (-0.604**) and positively with qP (0.606**). Thus, the study clearly indicates a relationship between the ABA accumulation under chilling stress and extent of injury in maize according to the hypothesis that CT in maize is related to the ability for the accumulation of ABA under chilling stress conditions.Badano rolę ABA w odporności na chłód siewek kukurydzy na nowym zestawie linii wsobnych kukurydzy o ustalonych różnicach w odporności na chłód. W warunkach chłodu (4°C) poziom ABA wzrastał u wszystkich badanych genotypów. Wzrost ten był istotnie wyższy u linii odpornych na chłód w porównaniu z wrażliwymi. Między poziomem ABA a stopniem uszkodzeń chłodowych obserwowano istotną korelację. Poziom ABA korelował ujemnie z procentem uszkodzeń nekrotycznych (-0,604**) a pozytywnie z qP (0,606**)

Poziom kwasu abscysynowego u siewek kukurydzy w warunkach polowych podczas wiosennych okresów chłodu

Laboratory studies have showed higher ABA accumulation in seedlings of the chilling tolerant genotypes than in the sensitive ones during low temperature exposure. On the basis of these results the hypothesis was developed that chilling tolerance (CT) in maize is related to the ability for fast and pronounced formation and accumulation of ABA as a protective agent against chilling injury. Presented in the paper measurements of ABA levels in maize seedlings under complex field conditions during natural spring cold waves at two sites of Europe confirmed the results from growth rooms. The chilling tolerant maize lines accumulated under field conditions more ABA than the sensitive ones during spring cold periods. Moreover, the data from field conditions show that the ABA accumulation induced by low temperature is not directly related to chilling-induced water deficit.Badania w warunkach komór wzrostowych wykazały wyższą akumulację kwasu abscysynowego (ABA) w warunkach chłodu u siewek genotypów kukurydzy odpornych na chłód w porównaniu z wrażliwymi. Na podstawie tych wyników postawiono hipotezę, że odporność na chłód u siewek kukurydzy powiązana jest ze zdolnością do szybkiej syntezy i akumulacji ABA jako czynnika ochronnego przeciw uszkodzeniu roślin chłodem. Prezentowane w niniejszej pracy pomiary poziomu ABA u siewek kukurydzy w warunkach polowych podczas naturalnych okresów zimna, wczesną wiosną, w dwóch stanowiskach Europy potwierdzają wyniki otrzymane w komorach wzrostowych. Podczas wiosennych okresów chłodu linie odporne na chłód akumulowały w warunkach polowych istotnie więcej ABA niż wrażliwe. Ponadto, dane z badań polowych wykazują, że poziom akumulacji ABA w warunkach chłodu jest niezależny od indukowanego chłodem deficytu wody u roślin

Salinity increases CO2 assimilation but reduces growth in field-grown, irrigated rice

alinity is a major yield-reducing factor in coastal and arid, irrigated rice production systems. Salt tolerance is a major breeding objective. Three rice cultivars with different levels of salt tolerance were studied in the field for growth, sodium uptake, leaf chlorophyll content, specific leaf area (SLA), sodium concentration and leaf CO2 exchange rates (CER) at photosynthetic active radiation (PAR)-saturation. Plants were grown in Ndiaye, Senegal, at a research station of the West Africa Rice Development Association (WARDA), during the hot dry season (HDS) and the wet season (WS) 1994 under irrigation with fresh or saline water (flood water electrical conductivity = 3.5 mS cm-1). Relative leaf chlorophyll content (SPAD method) and root, stem, leaf blade and panicle dry weight were measured at weekly intervals throughout both seasons. Specific leaf area was measured on eight dates, and CER and leaf sodium content were measured at mid-season on the first (topmost) and second leaf. Salinity reduced yields to nearly zero and dry-matter accumulation by 90% for the susceptible cultivar in the HDS, but increased leaf chlorophyll content and CER at PAR- saturation. The increase in CER, which was also observed in the other cultivars and seasons, was explained by a combination of two hypotheses: leaf chlorophyll content was limited by the available N resources in controls, but not in salt-stressed plants; and the sodium concentrations were not high enough to cause early leaf senescence and chlorophyll degradation. The growth reductions were attributed to loss of assimilates (mechanisms unknown) that must have occurred after export from the sites of assimilation. The apparent, recurrent losses of assimilates, which were between 8% and 49% according to simulation with the crop model for potential yields in irrigated rice, ORYZA S, might be partly due to root decomposition and exudation. Possibly more importantly, energy-consuming processes, such as osmoregulation, interception of sodium and potassium from the transpiration stream in leaf sheaths and their subsequent storage, drained the assimilate supply