Potted Rosa × hybrida `Meijikatar' plants were produced at 350, 700, and 1050 μl·liter-1 CO2. At a stage of development where half of the flowers showed color, plants were placed into simulated shipping incubators for 5 days at 4 or 16 C.
Increased CO2 levels resulted in shorter production time, increased root dry weight, increased plant height, and reduced total chlorophyll in the upper leaves of the plants. Upon removal from simulated shipping, the number of etiolated shoots per plant increased with increased CO2 concentration. After 5 days in a simulated interior environment, higher shipping temperatures induced more leaf chlorosis, but there were no differences in leaf chlorosis due to CO2 enrichment.
Production in a dynamic photosynthesis optimized climate (DC) was compared to production in a traditional and more stable climate (TC). Production of a tropical plant species (Hibiscus rosa-sinensis L.) in a DC resulted in between 18% and 63% reduction in energy use, mainly due to lower temperatures and increased use of thermal screens. In high light periods, the average day temperatures (ADT) were virtually the same in the different treatments, while in low light periods both ADT and average night temperature (ANT) were lower in the DC. Differential use of the screens resulted in a higher cumulative light integral in the DC. The number of lateral breaks was either the same or higher in the DC. Dry weight at the end of the production period was not significantly different in six of the seven experiments, and in five out of seven replications, plants grown in the DC were shorter than plants in the TC. Production periods between 10 days shorter and 21 days longer, for the DC compared to the TC, could not be explained by temperature integration alone. In the DC, a high positive DIF (difference between ADT and ANT) does not seem to increase elongation growth. The study illustrates that it is possible to produce a heat-demanding plant and save energy using a DC.
Using psychrometric pressure-volume analysis, root water relations following drought were characterized in Rosa hybrida L. plants colonized by the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith. Measurements were also made on uncolonized plants of similar size and adequate phosphorus nutrition. Under well-watered conditions mycorrhizal colonization resulted in lower solute concentrations in root symplasm, and hence lower root turgors. Following drought, however, mycorrhizal roots maintained greater turgor across a range of tissue hydration. This effect was apparently not due to increased osmotic adjustment (full turgor osmotic potentials were similar in mycorrhizal and nonmycorrhizal roots after drought) or to altered elasticity but to an increased partitioning of water into the symplast. Symplast osmolality at full turgor was equivalent in mycorrhizal and nonmycorrhizal roots but because of higher symplastic water percentages mycorrhizal roots had greater absolute numbers of osmotic (symplastic) solutes. Drought-induced osmotic potential changes were observed only in mycorrhizal roots, where a 0.4 megapascal decrease (relative to well-watered controls) brought full turgor osmotic potential of mycorrhizae to the same level as nonmycorrhizal roots under either moisture treatment.
Chinese hibiscus ( Hibiscus rosa-sinensis L.) or tropical hibiscus is extensively planted as a flowering pot plant worldwide and as a flowering shrub throughout tropical regions. Hibiscus rosa-sinensis has not been reported from the wild and is
stone (Vivosun, Ontario, CA, USA) connected to an aerator (General Hydroponics, Santa Rosa, CA, USA) with an output for each container. Four lettuce plants in an independent 21.5 × 17.8 × 7-inch DWC reservoir (Rubbermaid, Atlanta, GA, USA) constituted an
Various uniconazole (Sumagic™) rates were either sprayed or drenched alone or in combination with 6-BA and GA4+7 (Promalin™) or dikegulac-sodium (Atrinal™) on Hibiscus rosa-sinensis `Brilliant'. The rates of uniconazole were 0, 5, 10, and 15 mg a.i./L; 6-BA and GA4+7, 25 mg a.i./L each; and dikegulac-sodium 1000 mg a.i./L.
Plant height was reduced by uniconazole when drenched at rates as low as 5 mg/L and 15 mg/L when sprayed. Dikegulac-sodium slightly counteracted the effects of uniconazole. Uniconazole activity was increased when either sprayed or drenched with application of 6-BA and GA4+7 resulting in greater height reduction.
Transpiration and stomatal diffusive resistance of plants drenched with uniconazole alone was erratic; however, when uniconazole was sprayed or drenched and mixed with 6–BA and GA4+7 or dikegulac-sodium transpiration increased.
, it has spread east with the aid of Rosa multiflora , a naturalized rose species host and has become widespread from the Great Plains to the East Coast of North America ( Amrine, 2002 ). This epidemic has spread to garden roses in home and commercial
Rooted cuttings of Hibiscus rosa sinensis L. cv. Leprechaun were irrigated with full strength Hoaglands solution containing 0, 2.5, or 10 mM K+. Half of the plants at each K+ level were subjected to a 21-day slowly developing drought stress cycle (DS) followed by a recovery period (day 22), while the other half were non-drought stressed (NDS). Midday leaf water potential (Ψleaf) at day 21 were -1.5 to -1.6 MPa for DS and -0.5 MPa for NDS plants. Photosynthesis (A) was lowest during early stress and recovery of 0 mM K+ plants. Transpiration (E), stomatal conductance (g), and instantaneous water use efficiency (A/E), were generally lowest in 0 mM K+ plants. During peak stress, A was highest in the 2.5 mM K+ plants, whereas E was lowest and A/E highest in 10 mM K+ plants. Ψleaf did not differ among K+ treatments during peak stress and recovery, but osmotic potential was highest (least negative) and turgor potential lowest in 0 mM K+ plants. DS plants had lower carbon isotope discrimination (Δ) compared to NDS plants at all K+ levels, suggesting higher A/E for DS plants. Although there was no significant K+ effect, there was a trend at peak drought stress of Δ lower A and higher A at the 2.5 mM K+ level.
Rooted cuttings of Hibiscus rosa sinensis L. cv. Leprechaun were grown in fine sand and irrigated with full strength Hoaglands solution containing 0, 2.5, or 10 mM K+. Half of the plants at each K+ level were subjected to a 21-day slowly developing drought stress cycle (DS) and the other half were non-drought stressed (NDS), which yielded a midday leaf water potential (Ψleaf) at day 21 of -1.5 to -1.6 MPa and -0.5 MPa, respectively. Drought stress reduced leaf area (LA), leaf area ratio (LAR), shoot, root, leaf and total dry weights of 2.5 and 10 mM plants and increased the root:shoot ratio of all K+ treatments. Increasing K+, increased all growth parameters measured in both DS and NDS plants, except for LAR, which was greatest at 0 mM K+. At 0 mM K+, drought stress did not affect LA, LAR, shoot, root and total dry weights. Neither drought nor K+ treatments affected specific leaf area (SLA). In NDS plants, K+ had no effect on percent live root ratio (PLR) as indicated by translocation of 86Rb+ from leaves into living roots, determined by autoradiography. Although drought stress reduced PLR at all K+ levels, PLR was greatest at the higher K+ levels.