Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.

Tomato seedlings (Lycopersicon escukntum Mill. cv Vendor) were grown hydroponially with their root systems maintained at a constant temperature for a 2-week period commencing with the appearance of the first true leaf. Based on fresh and dry weight and leaf area, the optimal root-zone temperature for seedlin growth was 30°C. The carbon exchange rate of the leaves was also found to increase with rising root-zone temperature up to 30°C. However, a more complex relationship seems to exist between root-zone temperature and the accumulation of 14C-labeled assimilates in the roots; inasmuch as there is no enhancemnt in this accumulation at the most growth promoting root-zone temperatures (22-300C).The effect of heating the plant root-zone or soil has been studied mainly to ascertain the minimum temperature required to insure satisfactory plant growth. Although root-zone temperature has been shown to affect tomato plant growth, the physiological basis for this response has not been thoroughly investigated. Most studies (4, 11,13,17) have elicited increased growth with warmed roots (25-30°C) and a decrease in growth when roots were cooled below ambient with a sharp decrease in growth noted at temperatures below 15. 0°C (14, 23).It has been demonstrated that the metabolic activity of a sink region can be modified by adjusting its temperature (21). Alterations in the source-sink relationship through modifications of their respective strengths have been shown to influence the translocation rates of sucrose from source leaves to sink regions (20) reflecting increased or decreased demand by these sinks. Furthermore, a correlation between sink-controlled translocation rates and photosynthetic rates of leaves which supply those sinks has been demonstrated (18). It is hypothesized that the physiological basis for increased growth of tomato plants at warm rootzone temperatures may be due to the effect of increased sink activity of the roots on increasing the CER2 of the leaves. With the cotyledons emerging from above and the roots hanging from below, the styrofoam was fitted tightly into a plastic bin containing 22 L of half-strength Hoagland solution (pH 6.0). The nutrient solution was thermostatically controlled to ± 0.5°C of the desired temperature and was kept at maximum level by adding half-strength Hoagland solution. The temperature of the solution had no effect on the temperature of the seedling shoot.Growth Studies. Growth studies were undertaken to characterize the response of tomato seedlings to a range of root-zone temperatures with the expectation of relating translocation and photosynthesis to growth.After a 3-d acclimatization period, during which the seedlings' roots were exposed to a nutrient solution temperature of 22C, the seedlings were subjected to a constant root temperature ranging from 10°C to 38.7°C.

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There is a general belief that the quality of tomatoes ripened on vine is better than tomatoes ripened off the vine, influencing among other parameters, the price of this commodity. We compared the quality of hydroponic tomatoes ripened on and off vine by chemical, physical, and sensory evaluation to find what attributes are affected and to what extent. Lycopene, ␤-carotene, total and soluble solids, moisture content, ascorbic acid, acidity, pH, texture, and color were analyzed. Tomatoes ripened on vine had significantly more lycopene, ␤-carotene, soluble and total solids, higher a* and lower L*, and were firmer. However, a 100-judge panel rated only the color and overall liking of the vine-ripened tomatoes as more intense than the fruit ripened off vine. Therefore, the chemical and physical differences were mostly not large enough to influence the panelist's perception. The characterization of tomatoes ripened on and off vine may help to guide post-harvest handling and treatment and to improve the quality of tomatoes ripened off vine.