The research was carried out under a greenhouse in Chapingo, State of Mexico, during 2007. Phenological behavior and fruit yield of thirteen bell pepper (Capsicum annuum L.) hybrids grown hydroponically were assessed. The hybrids Cyrus, Conan, Gandal, Grandísimo, Itzel, Orión, Triple 4 and Triple Star produce red fruits; Diego, Cadia, Giacomo and Moonset have yellow fruits, and Magno orange ones. A randomized complete block design with three replications was used, and the experimental unit consisted of six plants (1 m2). Phenolo¬gical and morphological variables were recorded, plus fruit yield and its components. The hybrid Giacomo was early, and its cycle, from transplant to the beginning of the harvest, lasted 91 days, while Grandísimo was a late hybrid, requiring 117 days to fulfill its life cycle. On average, seedling emergence occurred 16 days after sowing (das) for all hybrids evaluated, while the first, second and third true leaves appeared at 37, 47 and 61 das, respectively, and the first, second, third and fourth bifurcations occurred at 10, 17, 25 and 30 days after transplanting (dat), respectively. Phenological phases such as flowering, fruiting, fruit color change and beginning of harvest occurred at 33, 44, 93 and 102 dat, in each case. The Orión hybrid had the best fruit quality, averaging 178.7 g in weight, 9.2 cm in width and 7 cm in length, achieving the standard of top-quality fruits in the Mexican market. In addition, Orión had the greatest yield per plant (1.9 kg) and per area (11.5 kg.m-2); the Magno hybrid showed the lowest yield (5.7 kg.m-2).

In the roselle plant (Hibiscus sabdariffa L.), the transition from flowering to fruiting is gradual, resulting in both mature and immature calyces during harvest. To determine optimal harvest time, changes in size (diameter and length) and chemical characteristics (dry matter, pH and anthocyanin content) of calyces of three ecotypes (China, Reina and Criolla) in nine stages of maturity (flowering stage and then every four days until 32 days after flowering) were analyzed. Calyx size increased progressively until 20 to 24 days after flowering (stages 6 and 7, respectively), but the increase in subsequent stages was not significant. Calyx diameters ranged from 14.34 to 30.96 mm and length from 18.60 to 56.76 mm. The Reina ecotype had larger calyces and China the greatest diameter. Anthocyanin content ranged from 205.93 to 1110.74 mg.100 g-1 of dried calyces; China had the highest content from flowering until stage 6, whereas in Reina it increased gradually until stage 7 and in Criolla it peaked in stage 4. Anthocyanin content decreased after 20 to 24 days of flowering. Dry matter content decreased as the calyces matured, falling from 17.86 % to 10.43 % throughout the maturation stages, while pH showed slight fluctuations with values from 2.11 to 2.81. These results suggest that calyces reach harvest maturity 20-24 days after flowering.

The development of biotechnological methods of cryopreservation allows safe, long-term germplasm storage of valuable species such as chrysanthemum, which is one of the most important ornamental plants in Mexico and around the world. This study used the cryogenic methods of encapsulation-dehydration and vitrification to conserve chrysanthemum cv. Indianapolis White plants grown in vitro. Results showed similar behavior with both procedures during tissue recovery. The highest survival rates after cryopreservation were 60 % for encapsulation-dehydration and 74 % with vitrification. However, regeneration in both cases passed through a primary phase of callus formation and rates of obtention of new plants were low, 12 and 10 %, respectively. Therefore, further research is needed to improve cryoprotectective conditions in order to increase rate of recovery of chrysantemum plants.

Given the great biological variation in the infraspecific complex of Sechium edule, biochemical characterization of the fruit is needed; the¬refore, the objective of this study was characterizing one wild and seven domesticated varieties of S. edule fruits. The samples were taken from the Banco Nacional de Germoplasma in Huatusco, Veracruz, Mexico, during a period of three years. The assessed variables were: pigment content (chlorophyll and carotenoids), terpenic compounds, ascorbic acid, total soluble solids, titratable acidity, and epidermis color; principal components and hieralchical analysis was conducted for their evaluation. The results showed that there is biochemical variation among varieties having a common ancestor in wild relative chayote. Among the cultivated varieties there are four levels of varia¬tion that allow for grouping by higher biochemical similarity.

Standard germination test is used in seed industry to evaluate seed quality; however, since it is conducted under favorable conditions for the occurrence of germination, sometimes the estimated results are quite different from those observed in field. Therefore, the aim of the present study was to identify the vigor test more correlated to seedling emergence at field conditions. Eleven tomato varieties were subjected to a standard germination test, five vigor tests. Seedling emergence in open field and in polystyrene trays under greenhouse conditions was evaluated at Universidad Autónoma Chapingo. A completely randomized experimental design with four repetitions of 25 seeds was used. The evaluated characters were: germination and emergence percentage, speed of germination and emergence, shoot and root length, and seedling dry weight. The accelerated aging test was the most accurate on predicting emergence in seedbed condi¬tions; whereas the emergence test in trays in a greenhouse showed statistical similarity with the cold test and the ammonium chloride test. The response of the varieties depended on seed quality and the interaction with the evaluation test used.

A factor limiting the availability of onion seed is its accelerated postharvest deterioration. The research aim was to evaluate the recovery of seed germination in aged onion after application of chemical solutions. The onion seeds were artificially aged for 48, 96 and 144 h. Next the seeds were placed in solutions: gibberellic acid (3.46 mg•L-1), (BAP (2.25 mg•L-1), calcium chloride (55.50 mg•L-1) and potassium nitra¬te (50.50 mg•L-1), 8 to 12 h according to cultivar. The imbibed seeds were placed in standard germination conditions. The CaCl2 treatment in aged seeds (48 h) increased the percentage of normal seedlings in the cultivar Contessa. All other seed treatments increased the time to reach T50 and negatively affected germination. The use of BAP caused the higher reduction in the percentage of normal seedlings, lower seedlings biomass and the consequent loss of vigor. Toro and Contessa were the cultivars with greatest vigor, and Crystal white wax and Cojumatlán presented intermediate vigor, while Red burgundy showed the lowest vigor.

Crops face problems of agronomic management and diseases, increasing costs and environmental contamination. Ascorbic acid (AA) is an antioxidant compound which induces plant growth-responses to cope with stress. The effect of AA on chrisantemum (Dendranthema grandiflora Tzvelev) cv. Polaris under greenhouse condition was evaluated. Plants were sprayed twice a week with 0, 3.4 and 6.8 mM of AA from 30 days after transplant up to harvest time (100 days after transplant). AA significantly increased shoot length, dry weight, number of floral buds and stems per plant in contrast with control, being 6.8 mM the best treatment which enhanced biomass. AA significantly enhanced protein content (36 %), total photosynthetic pigments (75 %) and peroxidase activity (33 %) respecting the control, these res¬ponses were associated to the evaluated growth parameters.