European and in particular German growers have to struggle with environmental programs, public concern, drastical decrease in the number of available pesticides and high costs for manpower and energy. Some of these problems may be solved by soilless cultivation and/or recirculating irrigation systems.   For pot plant cultivation closed subirrigation systems (troughs, flooding benches) are widely used in European greenhouses. In Germany in an increasing extent also for the outdoor production of pot plants and woody container plants. As far as soilless cultivation is concerned open system are still predominant in cut flower and stock plant production. The hesitant introduction of soilless, closed irrigation systems may be due to high investments and growers fear of spreading diseases.   A closed irrigation system is defined as one in which losses of water, nutrients and pesticides are widely avoided thus preventing pollution of soil or ground water. Depending on the path of water movement, recirculating irrigation systems can be classified as demonstrated in figure 1 (Molitor and Wohanka, 1992). Case A describes systems in which nutrient solution is applied to the top and drain water is collected after passing through the roots and the substrate, e. g. rockwool culture with trickle irrigation. Case B demonstrates subirrigation systems in which the nutrient solution is applied to the bottom and soaks up into the root zone while the rest of the nutrient solution remains in the circulating system, e. g. subirrigation with pot plants. Case C represents substrate free cultivation such as NFT, plant plane hydrponic or aeroponics in which the bare root system is continually in contact with the circulating solution. The risk of disease dispersal depends to great extent on the type of irrigation system and on the water movement is the root zone in particular.

-

This paper includes a general history of the botanical gardens in Mexico along with some prehispanic gardens (such as those of Iztapalapa, Oaxtepec and Tezcutzingo) and their characteristics. Also Vicente Cervantes created the Botanic Garden to aid the “Cátedra de Botánica”. During the Mexican independent era other gardens were developed including the Botanica Garden in Guadalajara which was designed to aclimatate rare and exotic plants used in urban reforestation. The Oaxaca Botanical Garden represented a new concept for the contemporary botanical garden in México. The actual situation of the botanical gardens in México is evaluated based upon the questionnaires administered by the federal Ecology Secretariat and the Mexican Asociation of Botanical Gardens. Today in Mexico, there are 11 established botanical gardens, 9 in consolidation, 14 in formation and 1 of them functions as reserve. The Mexican Association of Botanical Gardens promotes the contemporary and future roles of the botanic gardens in the conservation of endangered species along with such programs as the formation of national collections, satelites botanical gardens and twin gardens.

The botanical garden is an institution that carries out activities associated with diverse scientific studies about plants based on living collections. The basic roles of a botanical garden include: 1) research, 2) education, 3) conservation and 4) public service. The central part of a botanical garden is the living plant collection which can represent taxonomic groups, vegetation types, and classes of plants with anthropocentric importance. Based upon the perspective from the United States of America and Canada, nine phases of botanical garden development can be identified. The structure, activities and contributions of each period varied. The modern botanical garden began in 1544 in Pisa, Italy. The introduction and distribution of ornamental plants were one of the benefits derived from world-wide exploration by European botanical gardens in particular.   The role of botanical gardens in the development of ornamental plants has diminished from the last century. There is an excellent opportunity for botanical gardens to carry out exploration, evaluation and conservation of plants with ornamental potential as well as wild relatives of ornamental species domesticates.

The cicad Dioon edule (chamal, or tiotamal), is a wild, endemic plant in Mexico. It is threatened due to its habitat destruction, to the illegal collections, and to the wrong use by the street retailers (palmeros). It is an ornamental prized in the international market. Its conservation and propagation in a small “ejidal” nursery, we described.

An inventory of the more common ornamentals used in public and private gardens was made for the Valley of Mexico. 344 species were recorded, 121 native to Mexico and 223 exotics. Some samples are listed according to the biological form and use in gardening; common and scientific names, the family and their origin are mentioned.

The fungicidal effect of hexaconazole (Anvil, ICI de México) foliar sprays in the control of powdery mildew (Sphaerotheca pannosa W. Fr.) in rose (Rosa sp.) was evaluated under greenhouse conditions in Xocotlan-Texcoco, Mexico, in a recently pruned plantation. During a four month period, dosage (0.00 0.10, 0.25 and 1.00 ml/l) and spraying frecuencies (every 8, 14, and 28 days) were combined, including a positive control (karathane, 1.0 ml/l every 8 days). There was no initial infection. However, its increase was not related to the severity of treatments, although, the most severe (1.0 ml/l hexaconazole every 8 days) maintained low incidence of the pathogen, up to the point in which its effectivity was more than 90 % even a month after the last spray. Moreover, the economic analysis shows that this treatment was by far superior to the rest with respect to flower production.

It is an old custom of all the nations to honor the memory of the dead. The flower species used I these rites vary with time due to the diversity of species offered; their colours are changing and so is the custom of the flowers used to decorate the burial place. In México Tagetes is the flower of the dead. In several European countries the pot Chrysanthemum is the principal flower for the Day of the Dead, however now, the white colour of Chrysanthemum it is not an exclusive one.   Many years’ observations conducted in the area of Texcoco, State of Mexico and lately in Puebla, Pue., indicate that the genus Tagetes has been partially replaced by other species.

The present customs have their roots in previous cultural development of the ethnos. These and the acceptation of Christianity resulted in formation of the custom to decorate and venerate the Cross – the mean of God’s love in sacrification for his people.   The vivid colors of cross decoration – the red of chamaki (Heliconia spp.) (Musaceae), the white of Zantedeschia aetiopica L. Spreng (Araceae), the green of foliage of chamaedorea palm (Chamaedorea tepejilote Liemb.) (Palmae), the blue of Hydrangea macrophylla (Thunb.) Ser. (Saxifragaceae), the pink of Lagerstroemia indica L. (Litraceae) join the cultural, aesthetic, prehispanic ethic formation that wishes to thank for God’s mercy on the sins of human being and asking for rain for their “milpas” – crops.

The results of an introductory study of the city’s flower market stands and flower shops are presented. The shop personnel was asked to respond a questionary. The city was divided into four quarters for the purpose of the study. The persons were in most cases the stand or shop owners. Sometimes employees responded. The study had an overall positive acceptance, except for one quarter in which only two persons of the 17 interviewed refused to answer.   The following conclusions were reached. The dates of major demand are: Saint Valentine (14 of February), day of mother (10 of May), graduation period (June-July), the secretary’s day (July the 21st, All Saint’s Day and Day of the Dead (1-2 of November), Festivity of the Virgen of Guadalupe (10-12 of December). During this time the flower’s demand and theirs price are reaching highest levels. The market stands are offering lower number of flower species, while the flower shops are reacher supplied-6 and 15, respectively. Red, rose and salmon like roses, white chrysanthemum and carnations of all colors are best selling. The flower shops are offering flowers of much wider range of colors as compared to the city’s market stands. Only flower arrangements are sold.

The use of howthorns in landscaping is being discussed. The hawthorns, originated in Mexico, represent ornamental values and are characterized by a wide adaptation to soil and climatic conditions. One should make use of the high variability of ornamental characters in landscaping the streets, home gardens, as well as home and office interiors. A large collection of howthorn types is located at the Department Fitotecnia, University Autonoma Chapingo, Chapingo, state of México.

In order to determin if greenhouse tomatoes growing under a soilless culture system based on pinching of plants to leave just one or two inflorescences per plant and using high population densities (9, 16, 20 or 24 plants.m²) yield more and have better quality than the conventional system without pinching and normal population density (3 to 6 plants.m²) a trial with four tomato varieties (Hayslip, Florida, Floradade and Río Grande) was carried out at the University Chapingo in the State of Mexico. The evaluated variables were fruit number and yields per m², by plant and by fruit cluster.   There were no significant differences in yield m² between pinching to leave one or two fruit clusters, but there were significant differences when compared against the control without pinching showed the lowest yield. At higher densities of population yield.m² was higher; densities of 24 and 20 plants.m² yielded more than densities of 9 and 6 plants.m². Hayslip and Floradade yielded statistically better than Florida and Río Grande per m² and per plant.

“Huauzontle” is cultivated in small plots in Mexico City, as well as Puebla, Tlaxcala, Mexico, Morelos and Hidalgo States, where the management of crop is varied resulting in a wide range of yields. In 1980, an experiment was carried out in Chapingo, Mexico, with the objective of knowing the effect of plant density in different topological arrangements; for this purpose three distances between rows (60, 80 and 100 cm), and- tree distances between plants (20, 40 and 60 cm) with 1, 2 and 3 plants per each, were evaluated. Twenty-seven treatments with divided lots were used in four replicates with the experimental design of random blocks. The variables evaluated were: Height of plant, diameter of stem, length of the first branch; and length, diameter and weight of panicle. It was found that in low density plants there were heavier panicles but low yields per hectare were obtained with a topological arrangement of 80-20-2, 31.8 t·ha^-1 was harvested.

The efficiency of selection for harvest concentration and earliness in 33 000 and 50 000 husk tomato planta/ha using selection intensities of 1 and 5 % was studied. Development of advanced material, for these characters, aiming at the release of an improved variety was an objective of this study as well. In accordance with the results from two cycles, the main conclusions were: 1) The selection for concentration and earliness was effective. High mean value were focend (a with significant increase) in number and weight of fruit in two mass selected materials. 5-IVMS and 1 IVMS, derived from the “Rendidora” variety. 2) The largest gain, measured on the basis of the average number and weight of fruits per plant 70 days after transplant (earliness), was obtained from 1-MMS when a plant density of 33 000 plants/ha and a selection intensity of 1 % were used. 3) Of the seven genetic materials obtained from the cycle second, one had a mean weight of 1,157 kg and a mean number of fruits of 33.3 with a correlation of 0.89 keeping the other agronomic characteristics.

Mexico is one of the most important centers of plant genetic variability. Many plant species under domestication have evolved since prehispanic times, husk tomato among them. This study was undertaken with the main objective being the collection of wild and cultivated germplasm to be preserved in a gene bank. The strategy considered the study of herborized plants which led to the definition of four routes of collection. From the herbarium study, 35 species detected were distributed in 26 states in a wide altitude interval and mainly associated with dry climate. Germplasm collection was conducted in 11 states, yielding 111 materials mainly associated with moderate climate in altitude interval of 750-2,470 msnm. Collected materials were storage in the germplasm bank of native species in Chapingo at -4 °C and at 12 to 14 % relative humidity. Of these matrials, 9.91 % showed a critical number of potential plants and 30-63 % were cases not yet studied.

This experiment was conducted in the Chapingo, Mex., area to study important agronomical traits of 60 genetic materials of husk tomatoes which were collected from 11 states of Mexico. Highly significant differences were found for total fruit weight per harvest, total yield, number of fruits, fruit diameter, fruit weight, seed weight per sample, and fruit length. Additionally superior genetic materials for total yields and earliness, among other important traits, were found. The most promising materials were found to be 58GRO06, 82MEX06, 24GRO02, 76MEX05, 47GRO05, 49MICH18, 65GTO02, 69JAL18, and 06PUE01.

Twenty eight husk tomato half-sib families (Physalis ixocarpa Brot.) were evaluated from a 4 mass selection arising from the commercial variety ‘Rendidora’. The research work consisted of three phases: 1) crop evaluation in the field, 2) germination test, and 3) seed vigor. The objective was to detect the more promising materials in order to conform a synthetic variety. A randomized complete block design was used with three replications for the three phases. The evaluation showed that the families performed in a similar way in relation to its phenotypic expression, although a group of 6 families with a high yield potential were detected. It is, therefore, feasible to form a compound with these families and liberate it as a variety. Another group of 5 early families was detected, being these the most outstanding in the first picking.

In this study, 60 genotypes of husk tomato collected in several places of the Mexican Republic were grouped according to sugar content and acidity, a parameters that let us find differences among groups. The study was established in the Experimental Field of the Universidad Autonoma Chapingo, during the spring-summer cycle of 1991. The analyses were made using the Lane y Eynon volumetric method for determining sugar content and a simple titration method, with sodium hydroxide 0.1 N, for the sugars determination and simple titration method, with sodium hydroxide 0.1 N, for determining acidity. The results show that for totals and direct reduction sugar content, only two groups, with respect to the sweetest material were differenciated, the second group consisting of fewer than 15 % of the total of genotypes in both variables, not so for the variable acidity. No relationship between the variables and the origin the collected genotypes (wild and cultivated) was found; this means that such characteristics, have been not used yet by growers as a selection criterion. Nor was an evident relationship between sugars degree and acidity detected.

Besides being of more stable performance and requiring no sophisticated seed-industry facilities, synthetic varieties can constitute the raw material of a breeding program. The decisions as to whether a synthetic variety should be selected as the basis of a plant breeding program and the strategy to be applied must include considerations on the structure of its genetic variability. In this study the genetic variance of a synthetic variety formed by n unrelated and noninbred parental components is derived considering one locus model with multiple alleles. The magnitude of the additive and dominant components resulted dependent of n and the total genetic variance is impacted by the dominance effects of the homozygous genotypes and by the covariance of these effects and the average effects of the involved alleles.

This study was performed in Chapingo, Mexico in 1990, having as the main goal the evaluation of effects produced by foliar fertilizer when applied in different doses, in yield and cuality of husk tomato (Physalis ixocarpa, Brot). The variety used was the Rendidora, which has different growing patterns. The evaluated factors were products (Nitrophoska, Bayfolan Forte, Greenzit and Tricel-20) and doses (2, 4 and 6 leter or kg·ha^-1). In a complete factorial manner, the experiment was conducted using a complete randomized block design using four replications. The evaluated variables were those related to the height and yielding ability of the crop. The foliar products at different doses did not show significant effects on yield. The product which generated the greatest volume of fruits in the second harvest the Tricel-20 (6 leter·ha^-1).

The study was done with the aim to determine the best cover plastic in the hibernal production of nopal below row tunnels and the differences with nonprotected area. The experiment was carried out in a 3-years-old. Calibers 400 y 600 plastics in semicircle row tunnel with height of 1 m, width of 2 m and length of 10 m, were used, and the total production obtained in 7 harvest made with intervals of 15 days, was evaluated. There were not differences between plastics with respect to the protection against low temperatures; under no plastic cover, yield had the lowest values. Differences in yield among intermediate and later harvest, were found; in the intermediate harvest the lowest temperatures were presented.

Several treatments were applied to seed of sweet granadilla in order to determine the best pregerminative method. Gibberellic acid at 50, 100, 200 mg·litro^-1, stratification during 12 ad 24 hours at 5 °C, running water during 12 and 24 hours, washing and control were the treatments. In the last evaluations the highest percentage of germination was worth stratification during 200 hours but this was not statistically different from the control. The beginning of germination was between 19 and 25 days after the sowing, although the maximum increase was between 30 and 60 days.

Survey type of investigations were conducted in one grape plantation in the State of Zacatecas (22° 32’ Latitud N and 101° 39’ Longitud W), 2,120 m above the sea level with climate type BS₁Kw. The 25 ha plantation was started in 1978. Yearly, 15 cm of water, in four irrigations, was applied. The fertilization 1 t·ha^-1·year^-1 of 2_1 or (NH₄), SO₄⁺ simple superphosphate (136-68-00), with additional application of cow manure at 20 t·ha^-1·year^-1, to the cv. Cardinal only. Normal practice of pest and disease control measures were applied. The cultivars evaluated were: Cardenal, Emperador, Morroco, Italia, Tokay and Carigane, they were 6, 5, 6, 5 and 7 years old, respectively. From each cultivar were sapled 3 sites, each site included 5plants (15 per cultivar). The soil samples included horizons A, Bw, from each site and cultivar, having total of 36 samples with two additional one from virgin soil. Analysis were don according to the procedure accepted in the laboratory. Both the fertility and salinity (saturation extract) were run. The results were as follow. The depth of A horizon varied from 20-43 cm and Bw horizon from 20-72 cm with soil rock (rhyolite) located from the soil surface at 40 to 72 cm.

Root distribution was studied in the profiles of the soil in six cultivars established from cuttings. The results were related to plant and yield components with following conclusions.   The number of roots was higher in horizon A. All cvs. presented a higher number of roots 2 mm in diameter. The roots of cvs. Italia, Emperador and Carignane were of higher regenerative power. The root growth in length was highest in cv. Carignane and lowest in cv. Tokay, during the entire period of observation. The sum of generated roots per observation was higher in cv. Carignane and lower in cv. Tokay (IV-VII). The number of accumulated roots was lower in X in cvs. Emperador and Italia; in XI in cv. Carignane. From October to December the roots increased in all cultivars but Carignane. This coincided with the dry period (no rainfall or irrigation).

Sprays of ethephon (2-chloroethyl phosphonic acid) applied at 0, 100, 300 and 500 mg.litro^-1 were done in September 23^rd. and 30 th. In 1989, on ‘Jaffa’ orange trees, when fruits initiated to change color from green to yellow (color break), to evaluate its effect on fruit characteristics and injury to trees. Results showed no significative effects on internal quality characteristics as total soluble solids (TSS), acid TSS/acid ratio, juice percent; neither on size (polar and equatorial diameter), weight, fruit firmess and chlorophyll content, although in this last it was noted a tendency to decrease as rate of ethephon increased. An evident difference was obtained in fruit coor. Ethephon at 500 mg·litro^-1applied September 30 th. Was the best treatment to promote yellow color. Injury to trees was noted in drop leaf and drop fruits. Leaf drop percent and fruit drop number increased when ethephon rates were increased. Doses of 300 and 500 mg·litro^-1 were the ones causing more leaf and fruit abscission.

One of the main problems that the crop of the sweet orange in México has, is the concentration of the greatest part of the production in the period between October and April, causing prices to fall during this period. With the purpose of increasing the out-of-season harvest of the cultivar Washington Navel, applications of gibberellic acid (GA₃) at a concentration of 25 and 40 mg·litro^-1 in November. December and February, and application of ethephon at 600 mg·litro^-1 in May were done. The results show that gibberellic acid decreased the production of flowers, increasing the fruit set and did not produce any effect on the number of shoots; ethephon did not promote flowering in the summer and induced a large quantity o vegetative shoots.

Avocado plants of cv. Hass were used to study the behavior of some physiological and biochemical aspects under the condition of drought and irrigation. It was found that the photosynthesis, stomatal conductance, transpiration and water use efficiency were highly affected by water deficit and in re-watering recovery at permanent wilting point (PWP) and did not recover after 24 hours. The water, osmotic and tugor potentials, as well as the relative water content were similar under drought and irrigation, thus apparently osmotic adjustment was occurring. The proline content was significantly higher in PWP with respect to the control. The abscisic acid content was also higher in drought at PWP and was double that of the irrigate control.