Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon chmielewskii Rick, LA1028, were exposed to two CO2 concentrations (330 or 900 microliters per liter) for 10 weeks. Tomato plants grown at 900 microliters per liter contained more starch and more sugars than the control. However, we found no significant accumulation of starch and sugars in the young leaves of L. esculentum exposed to high CO2. Carbon exchange rates were significantly higher in C02-enriched plants for the first few weeks of treatment but thereafter decreased as tomato plants acclimated to high atmospheric CO2. This indicates that the long-term decline of photosynthetic efficiency of leaf 5 cannot be attributed to an accumulation of sugar and/or starch. The average concentration of starch in leaves 5 and 9 was always higher in L. esculentum than in L. chmielewskii (151.7% higher). A higher proportion of photosynthates was directed into starch for L. esculentum than for L. chmielewskii. However, these characteristics did not improve the long-term photosynthetic efficiency of L. chmielewskii grown at high CO2 when compared with L. esculentum. The chloroplasts of tomato plants exposed to the higher CO2 concentration exhibited a marked accumulation of starch. The results reported here suggest that starch and/or sugar accumulation under high CO2 cannot entirely explain the loss of photosynthetic efficiency of high CO2-grown plants.The enhancement of growth and yields by increasing the level of CO2 in the atmosphere has been reported for many species (6). However, the long-term effects of high CO2 levels on the physiological and biochemical behaviors of tomato plants need to be studied further. Many species lose their photosynthetic efficiency when subjected for an extended period to high concentrations of CO2 in the atmosphere (5, 9, 12), and become gradually less efficient in the use ofthe added CO2. In a recent study, Yelle et al. (21) (18) indicated that the decline of Rubisco2 activity could explain the acclimation to high CO2 levels. However, the hypothesis most often proposed to account for the negative effect of CO2 enrichment is the buildup of starch and sugar. Thomas et al. (16), Madsen (7), and Mauney et aL (8) suggested that the decline of photosynthetic efficiency of plants grown at high CO2 concentrations is caused by an accumulation of starch. reported that an accumulation of starch above a critical level causes a decline of CO2 assimilation, and Nafziger and Koller (10) showed that a high starch level is associated with low carbon exchange rates. The buildup of starch can consequently cause a disruption of the thylakoids structure and disorientation ofgrana (7,13

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Nursery and greenhouse producers, research and extension faculty, and representatives from allied fields collaborated to formulate a renewed vision to address water issues affecting growers over the next 10 years. The authors maintained the original container irrigation perspective published in “Strategic vision of container nursery irrigation in the next ten years,” yet broadened the perspective to include additional challenges that face nursery crop producers today and in the future. Water availability, quality, and related issues continue to garner widespread attention. Irrigation practices remain largely unchanged due to existing irrigation system infrastructure and minimal changes in state and federal regulations. Recent concerns over urbanization and population growth, increased climate variability, and advancements in state and federal regulations, including new groundwater withdrawal limitations, have provided an inducement for growers to adopt efficient and innovative practices. Information in support of the overarching issues and projected outcomes are discussed within.

Volume of water captured in a container as a function of sprinkler type, spacing, plant type, and container size was measured for marketable-sized plants. Percent water captured was calculated and a model to predict this value derived. Percent water captured was inversely related to the leaf area contained in the cylinder over the container when containers were separated, and with total plant leaf area at a pot-to-pot spacing. This relationship was independent of leaf curvature (concave vs. convex). Canopy densities were less related to percent water captured than leaf areas. Irrigation application efficiencies separated by spacing ranged from 37% at a close spacing to 25% at a spacing of 7.6 cm between containers. Container spacing, canopy shedding, and possibly some canopy retention of water later lost by evaporation were determined to be the main factors associated with the low efficiencies. The results suggest that higher irrigation application efficiencies would be maintained only if plants were transplanted to larger containers before reaching maximum canopy size rather than spacing existing containers to achieve more room for canopy growth.

Three species of woody ornamentals, Viburnum odoratissimum Ker Gawl, Ligustrum japonicum Thunb., and Rhaphiolepis indica Lindl. were transplanted from 3.8-L into 11.4-L containers and grown for 6 months while irrigated with overhead sprinkler irrigation. Irrigation regimes imposed consisted of an 18-mm-daily control and irrigation to saturation based on 20%, 40%, 60%, and 80% deficits in plant available water [management allowed deficits (MAD)]. Based on different evaluation methods, recommendations of 20%, 20%, and 40% MAD are supported for V. odoratissimum, L. japonica, and R. indica, respectively, for commercial production. Comparisons of plant growth rates, supplied water, and conversion of transpiration to shoot biomass are discussed among irrigation regimes within each species. Comparisons of cumulative actual evapotranspiration (ETA) to either shoot dry mass or canopy volume were linear and highly correlated. Results indicated there were minimum cumulative ETA volumes required for plants to obtain a specific size. This suggests that irrigation regimes that restrict daily ETA will prolong production times and may increase supplemental irrigation requirements. Thus the hypothesis that restrictive irrigation regimes will reduce irrigation requirements to produce container plants is false due to the strong relationship between cumulative ETA and plant size.

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Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations (330 or 900 microliters per liter) for 10 weeks. The elevated CO2 concentrations increased the initial ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity of both species for the first 5 weeks of treatment but the difference did not persist during the last 5 weeks. The activity of Mg2+ -CO2-activated Rubisco was higher in 900 microliters per liter for the first 2 weeks but declined sharply thereafter. After 10 weeks, leaves grown at 330 microliters per liter CO2 had about twice the Rubisco activity compared with those grown at 900 microliters per liter CO2. The two species showed the same trend to Rubisco declines under high CO2 concentrations. The percent activation of Rubisco was always higher under high CO2. The

Irrigation runoff water from a containerized landscape plant production bed was blended with rainwater from green house roofs in a constructed collection basin. Water from both the collection basin and an on-site potable well were characterized and used to grow foliage and bedding plants with overhead and ebb-and-flow irrigation systems. Over a 2-year period, a total of 18 foliage and 8 bedding plant cultivars were produced with plant growth and quality quantified. Alkalinity, electrical conductivity, hardness, and concentrations of nutrients of water from both sources were well within desired levels for greenhouse crop production. Turbidity and pH were relatively high from algal growth in the collection basin. However, substrate pH, irrigated by either water source, remained between 6 and 7 throughout the production periods. All plants at the time of finishing were of marketable sizes and salable quality independent of water source. No disease incidences or growth disorders related to water sources were observed. Results suggest that captured irrigation runoff blended with rainwater can be an alternative water source for green house crop production.