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Reaction of 21 days old cucumber plants on high nitrogen supply during the growth in the conditions of 70% and 30% fwc sand humidity was studied in the phytotron. Obtained results showed that nitrogen in concentration 24 mmol•dm-3 (9 mmol higher than in Hoagland's medium) increased WSD, gs, E, Pn, as well as content of some monosaccharides (ribose, glucose, fructose), disaccharides (saccharose, trehalase), proline and trigoneline but fresh mass of plants, leaf area and ci value in cucumber plants decreased. However the effect of higher N dose on chlorophyll content in leaves and its fluorescence parameters (Fv/ Fm , F v'/Fm' , ΦPSII, Qp i Qn) have not been noticed. Moreover, it has been shown that influence of supraoptimal N dose on the value of determined plant physiological activity index was considerably bigger in 30% than 70% sand humidity. The authors suggest that high concentration of nitrogen in medium evokes changes in metabolity of carbohydrates and nitrogen substances which lead to an osmoprotectans increase in plant celIs. In this way plants are more resistant to an environmental stress effect.
The effect of mechanical stress (partial defoliation and/or shoot decapitation) were studied on gas exchanges and growth of radish and rapeseed plants. Removal of older leaves increased transpiration rate (E) but it didn’t have any influence on net photosynthesis rate (Pn). Shoot decapitation and defoliation of young leaves didn’t influence the Pn of radish but it greatly decreased photosynthesis rate of rapeseed plants. The stress also changed pattern of assimilates distribution and the organs’ growth. In radish plants photoassimilates were translocated to hypocotyls whereas in rapeseed they were mostly used for the growth of leaves and roots. It is concluded that mechanical stress plays important role in sink/source regulation. In this way it has an influence on gas exchange, biomass distribution and the growth of plants. That processes also depend on the types (donor or acceptor) and age of defected organs and plants cultivars.
In pot experiments the influence of long chain aliphatic alcohols (hexacosanol - HEXA, octacosanol - OCTA and triacontanol - TRIA), which were used in concentration 0,001 mg dm-3 , on growth, assimilate partitioning and gas exchange of radish plants cv. „Krakowianka" and „Sopel lodu" were studied. The received results showed that triacontanol was characterized by higher physiological activity than remaining alcohols. TRIA significantly increased yield of mass, as well as it changed the pattern of distribution of assimilates in plants. Under its influence the rate of mass of leaves to mass of storage organs decreased as well as the share of mass of leaves in the total mass of both plant cultivars. TRIA stimulated the rate of net photosynthesis (Pn), howewer, it did not influence the other determined gas exchange parameters: substomatal concentration of C02 (ci), stomatal conductance for water vapour (gs) and rate of transpiration (Tr). Remaining alcohols (HEXA and OCTA) did not any influence on growth of plants and their gas exchange but only on distribution of biomass.
The effect or exogenous spermidine (0; 1 and 2 mmol dm•') on cucumber plant subjected to seven day drought (30% f.w.c.) were studied. Growth rate of plants, gas exchange. chlorophyll fluorescence. water saturation deficit in tissue (WSD), leakage electrolytes (EL) as well as the content of free proline were determined. The results showed that drought inhibited growth and gas exchange. decreased the potential efficiency of PSII (Fv/Fm) but increased the value of WSD, EL and the level of free proline in tissue. The spermidine treatment of plants immediately before drought influenced the decrease concentration of free proline. water dericit and leakage of electrolytes but the increase of stomatal conductance (g.). intensity of photosynthesis (Pn) and transpiration (E). Greater change on the course of primary photosynthetic reactions in PSU (Fv/Fm., ΦPSII, qP, qN) were not detected. The autors concluded. that in drought conditions exogenous spermidine together with proline induced by stress. contribute lo increase of water content in tissue and maintenance of the enzymatic activity of cells as well as they guarantee the integrity of cell membranes. Profitable effect of spermidine on the condition of cucumber in drought period shorted the time necessary for plants to come back to level of control treatment.
Praca przedstawia wyniki 2-letnich badań dotyczących wpływu nawożenia KCl lub K₂SO₄ na wymianę gazową, niektóre cechy morfologiczne liści i plonowanie pomidorów szklarniowych odm. ‘Romatos’ rosnących w piasku, wełnie mineralnej i torfie, przy zastosowaniu systemu fertygacji. Uzyskane wyniki wskazują, że siarczan potasu wpływa korzystniej na proces fotosyntezy, zaś chlorek potasu na proces transpiracji. Nie stwierdzono natomiast jednoznacznego wpływu obu rodzajów soli na liczbę szparek, długość ich szczeliny szparkowej i zawartość chlorofilu w liściach. Najwyższą intensywność fotosyntezy wykazywały rośliny rosnące w piasku, niższą w wełnie, a najniższą w torfie. Typ podłoża i rodzaj soli potasu nie różnicował wielkości plonu owoców uzyskanego z 1 rośliny. W pracy sugeruje się różnice w dystrybucji asymilatów dzięki którym rośliny żywione KCl, mimo niższej intensywności fotosyntezy netto, plonowały tak samo jak żywione K₂SO₄.
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