Temperature is one of the main factors that affects the growth pattern of Gerbera hybrida, which shows vast variation in morphology and stress adaptation among cultivars. However, little is known about temperature responses of plant growth among different cultivars. In this study, four cultivars were planted in different growth temperatures to investigate the effect of temperature on plant growth of Gerbera hybrida during their vegetative growth. Results showed that the optimum growth temperature of the four cultivars was 20 °C, of which plant height, root length, biomass accumulation, leaf area, and photosynthetic rate were enhanced significantly. Different cultivars showed diverse temperature adaptation ranges, which were related with their genetic background, and the temperature adaptability of cultivar Autumn was the best among the four cultivars. Temperature also had significant effects on photosynthetic rate, which was the main factor shaping plant growth. Our research provides the basic guidance for the growth temperature control in the cultivation of Gerbera hybrida.
Lycoris radiata has beautiful bright-red flowers with both medicinal and ornamental value. However, the mechanisms underlying an unusual characteristic of Lycoris radiata, flowering without leaves, remain unclear. In this study, climatic influences, biomass composition, and yearly variations in bulb contents across eight developmental stages of L. radiata were analyzed. Thus, L. radiata summer dormancy was investigated in three dimensions: climate-associated phenology, biomass distribution characteristics, and physiologic bulb changes. The results showed that dormancy was most strongly affected by high ambient temperature, followed by scape development, flowering, leafing out, vigorous leaf growth, flower bud differentiation, flower bud predifferentiation, and leaf maturation. Biomass allocation, bulb contents, oxidoreductase activity, and root activity fluctuated significantly in L. radiata among developmental stages. Relative bulb dry weight was greatest during the dormant period (95.95% of total dry weight) and lowest during vigorous leaf growth (November–December). Root biomass was also significantly greater during dormancy than during flowering, leaf maturation, and flower bud differentiation. Only root biomass during vigorous leaf growth was greater than root biomass during dormancy. However, in dormant bulbs, soluble sugar content, soluble protein content, root activity, superoxide dismutase (SOD) activity, and peroxidase (POD) activity decreased. Thus, summer dormancy in L. radiata only constitutes a morphologic dormancy of the aboveground plant; the bulb and root remain physiologically active. The results suggest that L. radiata is sensitive to both ambient temperature and light, and that summer dormancy is triggered by the synergistic stimulation of these two factors. Although temperature controls dormancy, it plays only a limited regulatory role during the L. radiata flowering period. Thus, it is difficult to induce flowering or regulate annual flowering in this species through temperature control alone.
Growth of cool-season grasses declines with increasing temperatures. The objective of this study was to determine the effects of elevated night temperature on turf quality, root mortality, and carbohydrate metabolism in creeping bentgrass (Agrostis stoloniferous L. var. palustris (Huds.) Farw (syn. A. palustris Huds.). Plants of `Penncross' were exposed to two night temperature regimes: 24 °C (higher night temperature); and 19 °C (lower temperature control) under the same day temperature (24 °C) in growth chambers for 45 days. Prolonged exposure of plants to higher night temperature reduced turf quality, canopy photosynthetic rate, whole-plant and root respiration rates during the day, translocation of newly fixed 14C assimilate to roots, and total nonstructural carbohydrate content in shoots and roots (including dead and live roots). Elevated night temperature increased root mortality and whole-plant and root respiration rates at night. Our results indicated that a decline in turf quality and increase in root dieback with high night temperature was mainly associated with increased night respiration rates of whole plant and roots and reduced carbohydrate availability.
Seedlings of Carica papaya L. `Waimanalo' (papaya) were transplanted into 27-L containers filled with nonsterile composted landscape yard trimmings passed through a 1.3-cm screen. At transplanting, papaya plants were inoculated with either one of three different AMF communities or were not inoculated as control plants. Two of the AMF communities were from Arizona citrus orchards, and one AMF community was from an undisturbed western Chihuahuan Desert soil. After transplanting, papaya plants were grown for 4 months under well-watered conditions in a temperature-controlled (32 °C day/24 °C night) glasshouse (45% light exclusion). Control plants remained non-mycorrhizal. Total colonization of papaya roots by AMF communities ranged from 56% to 94%. Depending on mycorrhizal treatment, AMF arbuscules and internal hyphae were present in 30% to 60% and 20% to 24% of roots, respectively. Noticeably absent in papaya roots were AMF vesicles. Papaya height, trunk diameter, and leaf phosphorus concentration were similar for inoculated and control plants. Compared with control plants, papayas inoculated with AMF communities had about 20% less shoot dry weight and about 50% less root dry weight. Under nonlimiting conditions in an organic substrate, AMF communities did not stimulate papaya growth but rather appeared to function as a carbon sink.
High temperatures are reported to promote day-neutral strawberry (Fragaria ×ananassa) vegetative growth and development and inhibit floral and fruit development, thereby imposing geographic and temporal limitations on fruit production. Day-neutral strawberry response to air temperature has been researched, but specific responses to temperature in the root zone have not. In a 1998 greenhouse experiment, 60 `Tristar' plants were grown hydroponically in a system of individual, temperature-controlled pots. A randomized complete-block design with constant root-zone treatments of 11, 17, 23, 29, and 35 °C and 12 replications were used. Stomatal conductance and transpiration rate were significantly lower for plants at 35 °C, compared with plants at all other temperatures. Leaf area and leaf dry mass of plants at 35 °C were five and four times smaller, respectively, than the combined mean for plants in all other treatments. Leaf area of runner tips was 450 and 44.5 cm2 at 11 and 35 °C, respectively, compared with that of plants at all other temperatures, 1552.1 cm2. Fruit dry mass was 14.5, 21.6, 25.5, 29.0, and 3.96 g per plant at 11, 17, 23, 29, and 35 °C, respectively. Root dry mass was highest at 11 and 17 °C and lowest for plants at 35 °C. The number of flowers, fruit, and inflorescences per plant was reduced at 35 °C, as were individual berry fresh mass and diameter. Overall, `Tristar' growth and development were near optimal at 17, 23, and 29 °C.
A study to determine the influence of light duration on seed germination was performed in a temperature-controlled growth chamber. Light treatments consisted of 0 (control), 6, 8, 10, 12 and 14 h of light exposure. Cool fluorescent light bulbs provided 19 μMol·m-2·s-1 light. Fifty seeds of each treatment were placed into separately labeled 6.0-cm-diameter petri dishes lined with Whatman #42 filter papers moistened with 2 mL of distilled water. Seed of both species germinated poorly in the control treatment. Mean time of germination (MTG) and germination percentage increased for both species when seeds were exposed to light. Pre-soaking seed in gibberellic acid (GA) significantly improved germination percentages of both species compared to the untreated control. Centipedegrass germination percentage and MTG also increased with light exposure. Carpetgrass seed germination was not enhanced by GA treatments with light exposure. The results of this experiment suggests that, if seed are covered too deeply, excluding light, MTG and percentage germination will be reduced. However, pre-soaking seed in a GA solution can improve dark germination by as much as 50% for both grass species.
The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.
Environmental conditions are known to affect the growth and quality of culinary and medicinal herbs. Hydroponic growing conditions often produces greater yields for many leafy crops compared to growth in more-traditional media. The objective of this investigation was to compare the yield and quality of sweet basil grown in continuous flow solution culture or well-irrigated Universal Mix. Sweet basil plants were germinated under mist and then transplanted to a continous-flow hydroponics system or to 6-inch pots containing Universal Mix. Rows of pots alternated with a row of hydroponic plants in a temperature-controlled greenhouse. Temperatures were maintained between 20 and 25 °C, the relative humidity was not controlled, pot-grown plants were irrigated as needed. HID lights added sublimentry irradiation and maintained a photoperiod of 18 h. Cohorts of plants were harvested at five time points between transplanting and maturity. Plants were divided into leaves, stems, and roots, dried, and the data subjected to mathmatical growth analysis. Several leaves from each plant were harvested and analyzed by gas chromotograpth for essential oils. Plants grown in hyroponics grew faster and produced more harvestable leaf material than the media-grown plants. Details of the plant growth analysis and the essential oil composition will be presented.
Vegetables are important in Mexican agriculture, and production under greenhouse conditions has been increased notably during the past year. The production area is about 3500 ha. The main crop grown in greenhouses is tomatoes, but bell pepper is a potential crop due to high yield and that good quality commands a good price during the winter. The objetive of this research was to evaluate nine bell peppers with high technology for horticultural production in the greenhouse. The experiment was carried out at the Experimental Station (INIFAP-CIRNO). The greenhouse conditions are: polyethylene (8 mL), without temperature control, natural ventilation, and soil condition (electrical conductivity of 1.22 dS·m-1and pH 7.96). The planting date was on 26 Oct. 2004. Plant density used was 3.78 plants/m2. The harvest period ocurred from 3 Mar. to 11 May 2005. In this period, we made six cuttings. There were no differences in the yield among varieties. The varieties with the higher yield were Laroles, Asaia, Far-114 and Cupid, with 65.6, 63.1, 63.1, and 57.4 t·ha-1, respectively. Cadia and Parker had the lowest yield, with 78.5 and 90.0 t·ha-1, respectively. The fruit weight was good in all varieties, however, Far-114 and Asaia had higher fruit weight with 272.5 and 269.5 g, respectively. The main insect pests during this experiment were white fly (Bemissia sp.) and leafminer (Lyriomyza sp.). There were no disease problems during this trial.
Weekly records of plant development, daily average temperatures (DAT), and light integrals (DLI) were used to develop a predictive model for time to flower, from seven successive plantings of the new Limonium sinuatum x Limonium perezii hybrid `LSLP4' under two light regimes, full sun or 50% shade. Plantings occurred over the period covering fall through to late spring in a temperature-controlled glasshouse under long days. DLI was highly correlated with the time to visible flower, explaining in excess of 80% of the variation. When combined with the plant growth parameter describing the rate of increase in either leaf number (LNAR) or groundcover index (GCIR), a second model was developed that was able to predict the date of visible flowers of LSLP4 and account for more variation than DLI alone. As a result of the uniformity of temperatures between successive plantings, DAT did not significantly contribute to explaining time to visible flower, but was significant for the period from visible flower through to flower harvest maturity. It is recommended that growers of `LSLP4' for cut flowers can use historical records of DLI to determine planting dates to schedule flowering. Once planting has occurred, by measuring actual DLI, DAT, and leaf number per plant, growers can use the second model to modify the predicted date for visible flowers and flower harvest.