The production of assimilates through photosynthesis and their distribution within the plant are important processes which help determine plant growth and develoment (Forney and Breen, 1985). Plant growth is a result of complex inter-relationships between physiological and morphological processes in the meristems, response to internal and external factors and supply of metabolites and inorganic nutrients (Moorby, 1981). Hence, efforts to improve plants growth and development (yield) must be related to those inter-relationships.

The destination of Spain’s fresh citrus fruit exports is mainly the European Union, a society with high buying power which demands high quality fruit. The most important fruit quality factors are size and appearance of the outer rind. This study is a review of the methods of control for these quality factors, preceded by a summary of what is now known to affect them.

n anatomical, physiological and biochemical study was done to establish some characteristic of photosynthetic pigment systems in coffee plants cultivated at full sunlight with different doses of nitrogen. A typical backventral structure of C-3 plants, with a great number of chloroplasts in both mesophyll cells and bundle sheath was observed under an optical microscope in histological cuts. Pigment separation was done by chromatography and higher values were obtained in Cla/Clb, carotenes/xanthophylls  and carotenes/Clb ratios for pigment system I in the flowering stage. Lower ratios in pigment system I were observed with increasing doses of nitrogen.

In papaya orchards, it has been observed that even when plants are healthy and well-nourished, a low percentage of fruit set occurs. This may be the results of inefficient pollination, the agents of which, are still unknown. This paper was done to determine the importance of pollinating agents (wind or insects) I the fruit set of seven-month-old papaya (Carica papaya L.), wax type or yellow, in central Veracruz, Mexico. One hundred blossoms at the point of anthesis  were chosen at random and covered with muslin bags (16 holes per inch). Another 100 blossoms were chosen and left uncovered as the control. Insects were collected from the flowers with a vacuum cleaner. Other variables were considered, such as sex of the plant, stem diameter at 40 cm from the ground, number of fruits set, length of the fruit, and number f open flowers on different dates at different hours. Of the covered flowers, 74 % were not pollinated, and of the control flowers, 62 % were not pollinated, indicating deficient pollination, low fruit set, and greater participation of insects as pollinators. The 712 insects that were collected were classified in 12 orders and 68 families. Floral aperture occurred between 7 and 9 a.m.

This study was done on trees with red thomy fruit and on yellow thomiess to determine flower differentiation. Samplings was done monthly. Flower initiation occurred the last days of August in thornless and at the beginning of September in the thomy type. The development of the vegetative meristem was modified, forming floral organs instead of leaves. In the transformation of vegetative into reproductive meristem a reduction in the number of layers of the tunica occurred, leaving only one layer. Flower differentiation followed and acropetal pattern in the fruiting shoots; buds of long and short fruiting shoots in the hawthorn were thornless. It was observed that there were more flower buds located at the base of fruiting shoots in the hawthorn without thorns which measured 1.7 to 11.2 cm in length. Generally, the flower buds were terminal buds. Buds located at the base of thorns were vegetative.

The quality and yield of pectin in hawthorn was characterized and compared with commercial pectin. It was found that hawthorn has 89 % more pectinic acid. The 7.4 % pectic acid and 3.6 % protopectin are characteristics which permit better gelling. Furthermore, the yield and quality of hawthorn pectin are higher than pectin extracted from the peel of citric fruits.

This work evaluates seven quality parameters (fruit weight, color, firmness, soluble solids contents, % acidity soluble solids % acidity, and ascorbic acid content) in five commercial strawberry cultivars (Chandler, Fem, Selva, Pájaro and Parker) and their progeny. The purpose of this study was to establish their commercial potential for use in a short term program of cultivar generation. Results showed a differential response among the treatments. Best fruit weight, firmness, soluble solids content and ascorbic acid were attained with the Parker variety and crosses of this with the other varieties. High hereditability was found for L color (brightness), soluble solids content and firmness (0.77 ± 0.54, 0.46 ± 0.55 and 1.0 ± 0.64 respectively).

The cultivars evaluated presented no difference in total length of vines, their fresh and dry weight, and the foliar area per plant, although the tendency was marked, especially in total leaf area and other compoenents. The cvs. Carignane and Italia gave the lowest foliar area while Emperador produced the largest. Highly significant correlations were found between the basal diameter of the vine and total vine length, node number in all cultivars. Also, total lengh of vines and total number of nodes per plant were highly correlated with the vine dry weight and the foliar area per plant. A number of regressions between vine components and yield components are listed. It was found that yield components, mass of berries, frutescence number, berry number, and Brix modiffed the size of shoots without influencing the cumulative plant index (stern components).

The cultivars varied in concentration of foliar nutrients as in ratios. Deficient or slightly deficient levels were found in the cultivars: Emperador, Tokay, Morroco, Carignane, Italia-N; Cardenal, Emperador, Morroco, Carignane, Tokay-P, Emperador, Morroco, Italia, tokay, Carignane – K; Cardenal, Emperador, Italia, Tokay, Carignane – Ca. Cardenal, Morroco, Italia, Tokay, Carignane-Mg. Excessive concentration of K was present in Cardenal and excessive Na in all cultivars excent Tokay. Fe was found in optimum amounts in all cultivars. Zn and Mn were optimum or in slightly excessive concentration. Although some elements are in optimum range, the ratios of nutrients indicate unbalanced nutritional conditions in all cultivars. Correlations among nutrients found were; (a) positivie N:P; K;Ca; N, K, Ca:Mg;K:Fe; K, Ca, Mg, Fe:Mn; Mg, Mn:Zn; P, K, Zn:Na and 8b) negative – N:K; Ca, Ca, Mn:Na; (c) positive or negative – P:Ca. A range of regessions was found of between nutrients in leaves of shoot components and leaf nutrients on yield components for each of the cultivars.

Cultivars varied in productive yield of grapes and sugar; being highest in cv. Carignane, Morroco and Tokay 11.1, 8.6, 5.3 t·ha^-1, and lowest in cv. Italia l.9 t·ha^-1. The estimated sugar yields were cv. Carignane 2178 and Italia 393 kg·ha^-1. The main productivity components were: number of infrutescences, weight and number of berries. The foliar area contributed to various components of infrutescence, the °Brix and weight of frutescences (cm²/°Brix; cm²/g). These coefficients were highest in cv. Emperador and lowest in cv. Morroco, Between °Brix and foliar area positive (cv. Cardenal, Carignane) and negative (cv. Italia) correlations were found. °Brix degrees was negatively correlated with size of vegetative components of plants. This reflected in a number of regressions found for aerial parts on °Brix. Average weight and number of frutescences, yield per plant and number of berries pe plant were highly correlated with all vegetative characters of shoots. The quantitative relations were modified by cultivar.

This work is a study of some variation parameters which define fruit quality of fifteen types of Stenocereus griseus H. (pitaya of may), raised on family farms in three localities of The Mixteca area. Such evaluations were perfomed during six years and there were found types with external and internal fruit characteristics which could be profitable for establishing commercial plantations.

The effects of endomycorrhizal inoculation, addition of organic matter, and plastic film mulch on the production of cantaloupe (Cucumis melo L.) in plastic tunnels were studied. The crop phenology was modified by plastic film mulch. Days to flowering and formation of fruits (both 7 days) and net (15 days) were decreased. The pests Trialeurodes vaporariorum, Epitrix cucumeris, Macrodactylus sp., Aphis fabae and Aphis gossypii were biologically controlled with entomopathogen fungi. The yield of cantaloupe was increased from 856 to 1,152 % by plastic film mulch, but the organic matter had no significant effect. The endomycorrhizal inoculation increased the yield from 22 to 60 % over the non-inoculated treatments. The use of these techniques of bioproduction are feasible in areas where production is not normally recommended. By adapting the methods to the conditions of the zone, good yields and quality can be obtained in less time.

This work was pefomed from May 12 to July 31 of 1993 in the “Rancheria Medellin and Madero, second section” from the municipality of “Centro”, Tabasco, México. Entomological samples were carried out every week in a white cucumber crop by three different methods; entomological net, pit-fall and hand check. 52 species of 38 families in nine orders were registered. 67.12 % were phytophagous, 18.78 % were predators, 6.07 % were parasitoids and 8.10 % were pollinaters and several other insects. The main species were Phytophagous. Acalymma pallipes, Diabrótica balfeata, Diaphania sp., Liriomyza sp. And Gryllus sp.; predators were: Aplomerus sp., Repipta sp., Callida sp. And Photinus sp.; and finally the pollinaters were Aphis mellifera. The population fluctuation of the insects was determinated for the crop phenology. The higher abundance occurred during flowering and fructification.

Looking for ecologically alternative methods in onion production, this experiment was dome at the Universidad Autónoma Chapingo during the spring-summer cycle in 1992. The main purpose was to evaluated biological, technical and economic response of this crop to the biofertilezer LEDA (Liquid Effluent from an Anaerobic Digestor). Applied soil treatments were done by linear meter to the crop 500, 750 and 1,000 ml of LEDA alone; another with 250, 500 and 750 ml of LEDA treatments combined with chemical fertilizer 60-40-00 kg of NPK, a chemical treatment with 120-80-00 kg of NPK was also included; another LEDA treatment of 1,000 ml was applied in gour parts to the foliage. Results showed that mixed LEDA and chemical fertilizer gave the best results in leaf number, meridional and equatorial bulb diameter. The highest value for fresh bulb weight (22.26 t/ha) was obtained when 750 ml of LEDA combined with 60-40-00 kg of NPK, having better results than chemical fertilizer (16.81 t/ha) and biological fertilizer (17.36 t/ha). Foliar application of LEDA avoided the attack of the pests and diseases at a low level.

Chemical weed control in husk tomatoes (Physalis ixocarpa Brot.) is nonexistent at present. Weed control has generally been in the traditional orm which is inefficient and unitimely. In order to find a more efficient alternative for control, herbicides were evaluated in husk tomatoes sown directly and transplanted in the experimental farm at the Autonomus University of Chapingo during the period of March to July, 1990. The treatments were trifluralina 1.5 and 2.0 l/ha; fomesafen 1.0 l/ha; oxadizon 1.5 and 2.0 l/ha; linuron l.5 and 2.0 kg/ha; diuron 1.0 and 1.5 kg/ha; bensulide 10 l/ha; oxifluorfen 1.0 y 1.5 l/ha; linuron + metalocholor 1.0 kg + 2.0 l/ha; two controls, one which was kept clean and the other overgrown with weeds. An experimental desing of random blocks was used with four replications. The results indicate that the treatments that resulted in good weed control without damaging the plant were trifluralina 1.5 l/ha, bensulide 10.0 l/ha, napropamida 5.0 l/ha, all of which showed yields that were statistically equal to the clean control.

A field experiment was carried out with 118 single selections of faba bean, cv. Cochinera Amarilla under two levels of moisture (0 and 20 % W. H.). The main objective was to study the effect of two levels of soil moisture on these selections during the fall-winter period of 1987-1988 in Chapingo, Mexico. From the surviving plants after a severe frost (-5.6 °C, after 70 days of the emergence), the grain per plant was recorded. These plants were classified in two groups (high and low grain yield). A t test showed a significant difference between the two mean grain yields. The low group was associated with the 20 % W. H. level of moisture. Levels of moisture also had a differential effect upon the numbere of effective pods and grains and rate of survival. Results also indicated that mechanism of recovery of damaged plants is production of shoots. In addition, the highest level of moisture was associated with the highest levels of plant damage.

The experiment was conducted in a greenhouse with a plastic cover (caliber 720) and the light intensity of 850 lux at cutting level. The shading nets (commercial products) were giving the following light intensities: 40 %-480 lux, 50 %-460 lux, 60 %-380 lux. The luminosity outside of the greenhouse (full light) was 1,050 lux. Four treatments were tested: 0, 40, 50, 60 % of shading net, with 24 cuttings/treatment. The substrate was tezontle + sawdust (4:6), with mist applied at an interval of 7 minutes. The percent of rooted cuttings 90 at 0 shading and 70 at 40, 50, 60 % of shading. The rooting occurred most rapidly at 40 % shading (10 days) The treatment without shading net gave response in: fresh weight of rooted cuttings, volume of the cuttings without roots, stem diameter, leaf number and plant dry weight. The 40 % shading net gave best characteristic of root volume, fresh and dry weight of roots, number and root length. The following regressions were obtained of solar radiation (Langley/day); fresh weight f cutting with roots, major stem diameter, leaf number, plant volume without root volume, fresh root weight, leaf surface and average stem diameter.

The purple cosmos is a native plant that has a great commercial potential as an ornamental. Currently in Mexico, the species is being domesticated, and as a contribution to this activity, this study describes three diseases of the cosmos. There is a high incidence of both Gall smut (Thecaphora mexicana Ell. And Ev.) and powdery mildiew (Erysiphe cichoracearum D. C.) in full grown cosmos plants, occurring during the flowering stage in wild populations. Also described is a necrotic spotting in seeds which was found to be caused by Alternaria tenuis Nees.

In 1988, sampling was done from 50 shoots of Tigridia pavonia Ker. Gawl (Iridaceae) from non-divided corns planted in November 1987. The objective was to obtain data on the relationship of the shoot height, number of shoots, and number of fruits with seed production. The following results were obtained: life of flowers is one day, but the flowering period is rather long and continues for one to two month. This is due to the time spacing of the flowering in individual inflorescences every one, two, three or four days and to the gradual entrance in flowering of each lateral inflorescence and the difference in the time of initial flowering of each plant. By planting the corns in groups in garden or pot, we obtained an extended flowering period. The number of flowers or inflorescences, as well as the number of seed yielded, depends on the height of the main shoot. The seed yield and quality (size) are influenced by, harvest date, the earlier one giving higher yield and seeds of larger size. From one fruit 79 seeds were obtained, and one shoot yields from 198 to 950 seeds.

A study was done on the methodology, evolution, and importance of ethnobotany. Mesoamerica is given special importance since it is the region which has given the world the best opportunities for ethnobotanical studies, especially in the in the central region Also, it is considered essential that mechanisms of public information be established in order to better preserve the accumulated knowledge and genetic materials. Furthermore, the importance of promoting a gradual change in the campesino communities toward living conditions that are more in accord with the modern world is stated.

Tepescohuite seeds are very difficult to germinate in a natural environment due to their hard seed. Coat.   Those seeds were set up under artificial conditions to germinate with different experimental treatments to overcome dormancy, such as: knife escarification, soaking in water at 80 °C (2, 5 and 7 min), rubbing escarification (10 and 15 min at 30, 40 and 50 % strength). Preliminary experiments were carried out in light and darkness.   Experimental data results showed that the highest germination percentage was knife escarification, soaking in water ( 80 °C/2 was 2 %. Light and darkness were not important for germination.

One of the manners of assembling a synthetic variety is based on inbred and unrelated parental components. When a synthetic variety which is formed by parental components of this nature and is intended to be used in a program of population improvement, it becomes important to have objective information on which the decision making process can be based as to the convenience of undertaking such a program and, if so, the strategy to be used. To provide information on which the plant breeder may make his/her decisions in these matters, in this study the genetic variance of a synthetic variety of the type under discussion is derived. The results obtained indicate that the magnitude of the coefficient of the additive variance components is directly and inversely related to the inbreeding coefficient of the parents and to n, respectively, where as for the dominance variance these relationships occur in the apposite  direction. The variance of the case in which the parental components are lines resulting form x generations of selfing is derived as well.

Estimation of the genetic components of variance of a synthetic variety is a way of obtaining useful information for making the decision as to undertake, or not, a program of recurrent selection on given population and, if so, the strategy to be applied. When the synthetic variety has been formed by n inbred and related parental lines, the estimation of the genetic variance components that ignores the presence of the inbreeding processes might yield results different from those obtained considering the actual situation. In this study the genetic variance of the synthetic variety under discussion is derived and the effect of neglecting the inbreeding coefficient (F) in the estimation of the additive variance (σ) is analyzed. Results indicate that: (1) this estimation produces a positive bias of F σ and (2) the precision of the estimation is smaller relative to the appropriate estimator’s; the variance of the former is 2F + F² times larges than the one corresponding to the unbiased estimator.

Chilli (Náhuatl) or, chilli, or pepper, Capsicum sp. L., is the number one spice ingredient in the world. Chile is a nutriticus and healthy food that might even have anticancer properties. The increasing commerce of peppers has created an unprecedented demand for their production in the tropical and temperate regions. Peppers are susceptible to a complex of viral diseases and their arthropod vectors. Important viruses are tobacco etch virus (TEV), pepper mottle virus PeMV), cucumber mosaic virus (CMV), potato virus Y (PVY), chilli venial mottle (CVMV), pepper severe mosaic (PSMV), tobacco mosaic virus (TMV), tobacco ring spot virus (TRSV), tomato spotted wilt virus (TSWV), germiniviruses, and beet curly top virus (BCTV). A breeding program was initiated to develop multiple disease and insect resistant cultivars. Several genotypes possessing heritable resistance to local isolates of TEV, PVY, TMV, PeMV, were identified. These stocks were hybridized with the best commercial cultivars of bells, long green/red chile, jalapeño, serrano, ancho, pimiento, cayenne, cherry and yellow wax pickling types.

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