Nitrogen metabolism in cucumber cotyledons and leaves exposed to the drought stress and excessive UV-B radiation

Plants absorb light energy for photosynthesis, and some amount of potentially damaging range of solar radiation, ultraviolet B. It accounts for less than 0.5% of the total solar radiation and the ambient current level of UV-B during the growth season provide 10 kJ·m–2 energy per day on the Earth’s surface. In the field conditions, increased UV-B radiation is often accompanied by drought, but negative effect of combined stresses is not so deleterious as the effect of one of them alone. We studied some changes in nitrogen me deficit and UV-B radiation. The stresses generally decreased the biomass and total dry matter production. Combination of water deficit and UV-B activated a stress tolerance mechanism in cucumber seedlings. The NR activity and synthesis of UV-B absorbing compounds were induced. Protection against UV-B radiation can partially involve increased production of UV-B protective pigments – slightly increased the SPAD value in cucumber cotyledons and leaves was observed. The deleterious effect of combined stresses was weaker than their additive or individual effects

Vase life of Heuchera L. leaves following the application of benzyladenine

The aim of this study was to assess vase life of leaves harvested at two dates – in the spring and summer, for 3 cultivars of Heuchera L. following the application of benzyladenine in spraying of maternal plants one day prior to leaf harvest. Leaves of cultivar ‘Southern Comfort’ were most durable, while those of cultivar ‘Purple Petticoats’ – least durable. Leaves harvested in summer had a longer vase life, except for leaves of cultivar ‘Plum Royale’. BA (300 and 600 mg·dm-3) in leaves of cultivar ‘Plum Royale’ improved vase life only in leaves harvested in the summer. BA (100 and 300 mg·dm3) in cultivar ‘Purple Petticoats’ – in leaves harvested in spring, while when used at a concentration of 300 and 600 mg·dm-3 – in those collected in the summer. BA (100–600 mg·dm-3) in cultivar ‘Southern Comfort’ considerably improved vase life of leaves cut in the spring and summer. BA inhibited protein degradation. In the tested cultivars in leaves, harvested in the spring and summer, treated with benzyladenine the content of saccharides was higher

Influence of rootstocks and the time of grafting procedure on the efficiency of propagation by grafting two cultivars of mountain pine (Pinus mugo Turra) and estimation of chloroplast pigments level in the needles

The experimental studies were conducted from 2015–2017 years in two cycles. The aim of the research was to determine a better grafting time and a choice of an appropriate rootstock for the propagation of two cultivars of mountain pine (Pinus mugo Turra). The influence of the grafted cultivar and rootstock used on the level of chloroplast pigments in the needles was also checked. The studies concerned two cultivars of mountain pine (Pinus mugo) ‘Grześ’ and ‘Zundert’, which were grafted on four different rootstocks: Pinus contorta (Dougl. ex Loud.), Pinus nigra (Arn.), Pinus sylvestris (L.) and Pinus mugo subsp. uncinata (Ramond Domin) in two dates: 20 January and 15 March. The highest percentage of graft success was obtained for the two cultivars on Pinus uncinata and Pinus contorta rootstocks. A later term of grafting procedure affected bigger effectiveness of grafting of the two studied cultivars, except for the graft success on Pinus sylvestris rootstock. The highest increments of side shoots and lengths of main stems for ‘Grześ’ cultivar were obtained on Pinus nigra, and for ‘Zundert’ the influence of the rootstock on the above mentioned parameters was not evident. No significant differences in the number of increments in the first and second year of studies were observed. The highest level of chlorophyll A and B was found in the needles of ‘Grześ’ cultivar, independently from the rootstock used. Among tested rootstocks, only Pinus nigra had a significant impact on a higher content of chlorophyll B in the needles of the studied cultivars of mountain pine trees

Influence of rootstock and grafting method on the grafts success and growth of Cedrus deodara (Roxb. ex Lamb.) ‘Karl Fuchs’ plants

Experimental studies were conducted in 2015–2017 in the Department of Dendrology, Pomology and Nursery of Poznan University of Life Sciences. The aim of the research was to study the usefulness of three rootstocks: Larix decidua, Pinus armandii, Cedrus deodara and two grafting methods: side grafting and split grafting for propagation purposes of Cedrus deodara ‘Karl Fuchs’. In addition, it was evaluated how the rootstock and the age of cultivar shoots influenced the level of chloroplast pigments in the needles. A higher percentage of grafts success was obtained on Pinus armandii and Cedrus deodara using the side grafting method. Grafted scions of ‘Karl Fuchs’ produced the greatest number of lateral buds and the longest lateral increments of growth on Cedrus deodara root stock. Side grafting significantly improved the percentage of plants that restarted their growth in the second year of cultivation. The largest number of buds on two-year-old shoots were counted on plants grafted on Cedrus deodara using split grafting method. The rootstocks used in this experiment had a slight effect on the content of chloroplast pigments in the needles. Plants grafted on Pinus armandii had the highest level of chlorophyll B, and those grafted on Larix decidua – chlorophyll A/B ratio. The content of chloroplast pigments in the needles depended on the age of shoots. The highest level of chlorophyll A, chlorophyll B and carotenoids was observed when needles were collected from the last year’s growth

Comparison of Water Stress and uv Radiation Effects on Induction of Cam and Antioxidative Defense in the Succulent Rosularia Elymaitica (Crassulaceae)

Growth and photosynthetic characteristics, inducibility of the CAM pathway and the functioning of the antioxidant defense system were investigated in Rosularia elymaitica (Crassulaceae) under drought and UV stresses. Drought did not substantially affect the growth of the plants, but it significantly reduced leaf thickness as well as osmotic potential, water potential and relative water content. In contrast, UV radiation treatment affected neither growth nor the water relations of leaves. Water limitation for 12 days caused a significant increase in nighttime PEPC and NAD-MDH activity and an increase in Δtitratable acidity relative to well-watered plants. The nighttime CO2 net assimilation rate increased significantly in drought-stressed plants but was still negative, resembling a C3-like pattern of gas exchange. Twenty days of UV treatment, increased Δtitratable acidity slightly and increased only daytime PEPC activity, and did not affect other parameters of carbon metabolism. As judged by maintenance of membrane integrity and stable amounts of H2O2 under UV stress, the antioxidant defense system effectively protected the plants against UV radiation. In contrast, oxidative stress occurred under severe drought stress (20 days of withholding water). Except for higher daytime APX activity in the UV-treated plants, enzyme activity in the control and in the drought- and UV-stressed plants did not show any diurnal fluctuation during 24 h. Temporal changes in Δtitratable acidity and ΔPEPC activity coincided closely with those of antioxidant enzymes; both started to increase after 12 days of drought stress. These results indicate that drought stress but not UV radiation induced the CAM-cycling pathway in R. elymaitica