Flowering in Sprekelia formaosissima (L.) Herbert. (common names: “pata de gallo” and “acamayo”) was evaluated. Bulbs were planted in plastic bags filled with volcanic soil (1st system: watering twice a week) and directly in the field (2nd system with natural precipitation). Five bulbs per clone were used in the first system and 10 to 12 bulbs in the second. The main objective was to obtain data on the yearly distribution of flowering. The most abundant flowering occurred in April and May. Some bulbs grown in the field produced a few flowers beyond these two months. The third population of plants studied in one home garden of Puebla flowered for six months. In this last case, flowering occurred in waves, separated by a period without flowers. Clones of bulbs with higher and lower flower production were identified. In general, bulb productivity (number of flowers per bulb planted) increased with the age of the bulbs. Flowering was found to depend on a critical bulb size. The data gathered suggest that the flowering period of bulbs varies among clones.

Avocados are susceptible to iron deficiency, and the ideal pH to grow them satisfactorily is 5.5 to 6.5. Conditions higher than pH 7 will probably cause iron deficiency. The symptomatology of iron deficiency is usually manifested as an interveinal chlorosis of young leaves while the veins remain green -hence the name iron deficiency chlorosis. Research on metabolism, biochemistry and physiology of iron in plants and avocado is discussed as well as approaches to control iron deficiency chlorosis in avocado. The best method to avoid iron deficiency would be to avoid planting avocados on highly calcareous soils, or to use rootstocks which are resistant to lime-induced chlorosis, on the other hand, several strategies have been developed to alleviate the problem of iron chlorosis. Apparently the only possibility to control iron chlorosis in established orchards is by soil applications of Fe chelates, since applications by foliar sprays have not been successful on a commercial scale. In the long term, development and use of avocado rootstocks with tolerance to calcareous soils or more Fe-efficient cultivars still seems to be the most economical solution to permanently control Fe chlorosis.

Total and reducing sugar content was quantified in determinate inflorescences (autumn) of ‘Colin V-33’ avocado, in leaves, and in indeterminate inflorescences (winter) of ‘Colin V’33,’ ‘Hass,’ and ‘Fuerte,’ in order to determine whether sugar content is different among inflorescences, parts of the inflorescences and cultivars. The research was carried out in Coatepec Harinas, Mexico. The to-tal sugar content was highest in ‘Colin V-33’ autumn leaves and inflorescences. The total sugar content was higher in the shoot of ‘Colin V-33’ indeterminate inflorescence. ‘Colin V-33’ determinate inflorescences had more total sugar content in their basal part (50.7 mg.g-1 f.w.), while the shoot of indeterminate inflorescences had the highest content (64.5 mg.g-1 f.w.). Comparing the three cultivars, it can be observed that ‘Fuerte’ had more reducing sugars in leaves and shoots (29.9 and 15.8 mg.g-1 f.w., respectively).

The behavior of sapodilla (Manilkara sapota L.) fruits cultivar Jesús María was observed during ripening, using two different kinds of wax to preserve the life storage and CEPA (2000 mg⋅litro-1) applications for ripening homogenization of the fruits. Sapodilla fruits we-re found to be climateric, with the respiratory peak occurring at the same time that ethylene production with 122.4 mg⋅kg-1⋅h-1 of CO2 and 93 mg⋅kg-1⋅h-1 of C2H4, respectively, four days afther harvest. The CEPA promoted homogeneous ripening, decreased phenolic compounds and accelerated ripening in more than one day. The wax did not help to increase the fruits postharvest life storage, but enhanced appareance and reduced weight losses significantly.

The purpose of this work was to evaluate the variation of soluble sugars and starch in peach (Prunus persica L. Batsch) with low chilling requirement. Two year-old peach trees of the cultivars and selections CP 91-9C, ‘Oro B’, ‘Oro Azteca’ and CP 91-16C were evaluated as treatments during the period January 1995 through July 1997 in the orchard San Jose belonging to the Colegio de Postgraduados, Mon-tecillo, state of Mexico. The trees were planted at a distance of 4 x 2 m conducted under the V system. The experimental unit used was one tree with five replications. The results indicate that soluble sugars showed a decreasing trend (57.8 to 14.9 mm•g-1 dry weight) dur-ing the sampling period, but it was only in the second sampling that there were differences (P=0.0002) among cultivars. Non-reducing sugars showed differences (P=0.0007) in the first sampling, the values varying between 12.2 and 83.8 mg•g-1 of dry weight. The content of total sugars was similar to that of non-reducing sugars and varied from 34.2 to 134.9 mg•g-1 dry weight, with differences among treat-ments in the first sampling (P=0.027). There were differences in starch content among cultivars in the sixth sampling. It was confirmed that the cultivars had differences in their phenological stages, that has to be with the accumulation and utilization of non structural carhohydrates of the leaves.

The objectives of this work were to evaluate the quality of the juice of yellow passion fruit (Passiflora edulis) and to determine the appropriate harvest time. The parameters evaluated were fruit growth, juice content, total soluble solids (tss), acidity, and total sugars of the juice. Analysis of fruits was done at harvest and after five days of storage under normal environmental conditions (23 ºC, 55% R.H.). Fruit growth stopped approximately 20 days after flowering (DAF). Fruit may be harvested 70 DAF. Fruit characteristics at the appropriate harvest time were: weight 82.5±18.5 g, polar diameter 7.4±0-89 cm, and equatorial diameter 6.1±0.6 cm, juice content 36 to 39%, tss 14 to 16%, acidity (citric acid) 4.5 to 4.8%, total sugars 8.3 to 9.1%, tss/acid ratio 3 to 3.4, and sugar/acid ratio 2 to 2.2. After storage in environmental conditions, the majority of the parameters presented few changes

The effectiveness of gibberellic acid on the delay of senescence and reduction of quality losses in ‘Valencia Late’ orange fruits was stud-ied in Cazones, Veracruz, Mexico. Twelve year-old trees were employed and sprayed with gibberellic acid in concentrations of 5, 10, and 20 mg liter-1 three times (the first of October, November and December), adding a total of three applications per treatment compared with a control. Fruit weight, juice content, peel color, chlorophyll, tritriable acidity, respiration and production of ethanol and acetaldehyde, were evaluated. The results showed that the application of gibberellic acid maintained the content of chlorophyll in the peel at values be-tween 90.3 and 117.5 μg⋅g-1, higher than those obtained in the control (44.4 μg⋅g-1). Respiratory rate was also lowered by the application of gibberellic acid. The application of gibberellic acid at 5 mg⋅liter-1 extended the harvest period by one month.

The objectives of this research were: a) to study the effect of several N-NO3:N-NH4 ratios on the activity of the enzymes nitrate reductase (NR) and glutamine synthetase (GS) and b) to identify the NO3- assimilation sites in prickly pear cactus (Opuntia ficus-indica (L.) Mill.). Five N-NO3:N-NH4 ratios (mg⋅liter-1 N-NO3:mg⋅liter-1 N-NH4) were studied [1:0 (150:0), 2:1 (100:50), 1:1 (75:75), 1:2 (50:100, and 0:1 (0:150)]. An experimental design of random complete blocks was used with four replications with a factorial ar-rangement of treatments. In shoot (cladode) and root, the activity of the enzymes nitrate reductase (NR) and glutamine synthetase (GS) were evaluated in vivo at 21 days after establishment of the experiment. High NR and GS enzyme activity was registered when the nutrient solution was supplied with a higher ratio of N-NO3:N-NH4, thus confirming the dependence of NR activity on the concentration of N-NO3 in the nutrient solution. Both enzymes had similar behavior, and more activity was detected in the roots.

Genotype, seed age, presence of malt extract coadyuvant and availability of ammonium and nitrate sources influenced the percent-age of somatic embryo formation obtained from nucellar tissue. There were embryogenetic responses in the nucellar tissue for 6 cul-tivars growing in 100% MS salt medium supplemented with 5 vitamins, 500 mg⋅liter-1 malt extract (ME) and additions of 600 mg⋅liter-1 of sodium nitrate (NaNO3) to the nitrate levels. Outstanding were the polyembrionic genotypes such as the cultivar ‘Chata’ (C. sinensis) with 53% and the mandarin orange 'Monica' (C. sinensis x C. reticulata) with 42%. Four cultivars produced somatic embryos when MS salt medium was supplemented with 500 mg⋅liter-1 ME, and the ammonium and nitrate levels were decreased 200%. The genotype Monica (C. sinensis x C. reticulata) was outstanding, showing embryogenetic responses of 60%. The nucellar tissue in grapefruit seeds (C. paradissi) at 22.2 weeks maturity showed no response in the medium used. Finally, the salt culture with 0.1 mg⋅liter-1 IAA, 0.1 mg⋅liter-1 kinetin, and 1.0 mg⋅liter-1 gibberellic acid (GA3), and media with MS salts, 500 mg⋅liter-1 ME, promoted the germination of nucellar embryos with 5 to 6 mm diameter after 6 weeks of culturing.

Sample of abortive ovaries of feminine plants of Cera type papaya was done to determine the concentration of N, P, and K, to study the anatomy, and to determine the presence of pollen on the stigma, pollen tubes and callosa in the funicle, using fluorescent microscopy. It was found that, based on dry weight, the senescent ovaries had equal concentrations of N (5.26 vs 5.07%) and K (1.51 vs 1.46%), and less P (0.44 vs 0.50%), compared with healthy ovaries. Anatomically, in the abortive ovaries a reduction in the size of the ovules and a degradation of the integuments were observed. As to the presence of pol-len and pollen tubes in abortive ovaries, in 80% they were found in the stigmas and in 90% they were found in the internal cavities of the ovary. Deposits of callosa were identified in the funicle in 90% of the abortive ovaries. Thus, abortion is proba-bly triggered by an asynchrony between the period required for pollen tube growth and the period of ovule viabili.

Biomas distribution of Cera creole type and cv. Sunset Solo papaya with different numbers of fruits per plant was studied. it was found that the biomass partitioned to leaves, petioles and stem was maintained nearly constant when the number of fruits per plant varied. at the same time, plants whit a low number of fruit had the same mean fruit weight as plants whit a high fruit set. Cera papaya was tower than cv. Sunsett Solo in dryfresh pulp weight and dryfresh seed weight, suggesting that Cera fruits have a low capacity for biomass attraction.

Observations of Crataegus, Malus Pyrus, and Cydonya, graffet onto Crataegus rootstock revealed that the grafts developed well after graffing. As the days passed, some grafts, especially Matus and Pyrus, showed necrosis, which resulted in death of the whole relationship, although many grafts done ten years ago are in good condition and producing well. this indication that Crataegus offers good possibilities for its use as rootstock for different species, cultivars, and types of fruit trees Mexico.

Orchids are found in may tropical places. Their production has a double importance: as an ornament and as an important economic resource. The purpose of this study was to characterize the fungal population in orchid roots and study the ex vitro plant mycorrhiza-tion. Of the isolations we selected 25 strains of Catleya sp., Encyclia belizensis, and Oncidium sphacelatum from roots. Fusarium was found to be the most common genera present. Inoculation with orchid mycorrhizal fungi (Rhizoctonia solani strain C96/45 and C96/48) produced a positive effect on the establishment and development of plantlets with 19.44 and 97.82% dry leaf mass and 52.61 and 57.5% dry root mass, respectively. The strain C96/48 was the best.

To reduce damage by Rhizoctonia solani Kühn on broadbean, several treatments, alone or combined, were studied: Two fungicides, barley straw (BS), alfalfa straw (AS) and solarization (Sol.). The variables evaluated were: Percentage of infection, number of emerged plants, number of dead plants, plant height, number of pods per plant and yield in two growing seasons. According to the results, with the treatment BS + quintozene + Sol., less infection occurred, followed by BS + benomyl + Sol., in both growing sea-sons. In the treatments BS + benomyl + Sol., BS + benomyl, and BS + quintozene + Sol., the greatest number of emerged plants and the lowest number of dead plants were observed. In addition, for plant height, number of pods per plant, and yield, the treatments BS + quintozene + Sol., BS + benomyl + Sol., and BS + quintozene were the best, although, in general, the BS + quintozene + Sol., were outstanding among the treatments. The fungicides quintozene and benomyl alone resulted in fair control compared with the best treatments. However, supplemented with barley and solarization, they were more efficient. The treatments alfalfa straw and alfalfa straw + solarization showed a greater percentage of infection, fewer emerged plants, lower plant height, and lower yield.

The origin, present state, and elements that constitute Mayan homegardens are studied. Their vertical and horizontal plant structure are analyzed. The "canché”, “eras”, animal, tree, and medicinal-ornamental subsystems are described, emphasizing their structure and functions in space and time.