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Objective. 'lo agronomically and physiologically evaluate the development of lettuce cultivars under protected conditions. Materials and methods. Under a completely randomized block design, the growth, agronomic and physiological characteristics of five lettuce cultivars were evaluated in two protected agriculture systems and in open field conditions. Results. The cultivars White Boston and Romana Parris Island Coss in house mesh and open field had the highest values in physiological variables (Photosynthesis close to 25.00/¿mol CO2 m2/s, transpiration greater than 7.00 mmol water m2/s and stomatai conductance greater than 1.50 mmol water mmol agua m2/s), which caused the highest values in fresh biomass area and root (95.90 and 3.55 g). The photosynthesis variable in plants sown in the open field reached values of22.29/¿mol CO2 m2/s, compared with house mesh and greenhouse with 17.14 and 14.16/¿mol CO2 m2/s. Conclusions. The ability of these lettuce cultivars to tolerate heat stress was due to morphological and physiological mechanisms, including long-lived leaf, stomatai control, and high photosynthetic potential. [ABSTRACT FROM AUTHOR]

Studies of shade effects on native forage species support pre-breeding process and are useful to establish selection criteria in plant breeding programs for the agroforestry systems prevailing in the Argentine livestock production. In the present study, ecophysiological and agronomic traits were evaluated in accessions of Macroptilium lathyroides belonging to the germplasm bank "Ing. Agr. José M. Alonso" of the UNL, under both natural and artificial light conditions. The general response has been related to a shade-avoidance strategy, where plants showed longer stems and greater leaf area in detriment of root and leaf biomass. Even so, accessions without a significant stem and root biomass reduction under shading were identified. However, stomatal conductance and photosynthetic rate were affected on all accessions subject to shade, independently of the produced biomass relative to control. [ABSTRACT FROM AUTHOR]

The use of conglomerate for the development of mycorrhizal inoculants is very important to develop a variety of commercial products made from these microorganisms. According to this a experiment was conducted in order to compare the effect of two mycorrhizal inoculants on growth, development and gasses interchange of maize plants. The experiment was developed under a completely randomized design and the inoculants proved were the first constituted by Glomus cubense specie and the other one was a conglomerate of species (Consorcio Selva). Different mycorrhizal (intensity and frecuence), physiological (stomatal conductance, photosynthetic rate) and growth (height, stem diameter and dry mass) indicators were evaluated. Not differences were detected among the inoculants employed on growth indicators, but in mycorrizal parameters the conglomerate (Consorcio Selva) presented the highest values of the indicator; however, an interesting behavior was observed using Glomus cubense inoculants due to the values obtained for this inoculants were comparable to control, but the effect of this specie was the best obtained on gas exchange variable. These results point to the highest efficiency of this specie and to the functional differences between species on ecological point of view, and they open the possibility of using of cluster in field's condition. [ABSTRACT FROM AUTHOR]

The present work was conducted with the objective of studying the behavior of growth, the net photosynthetic rate, stomatal conductance, hydraulic conductivity of roots and leaf water, osmotic and turgor potencials in seedlins of tomato plants submitted to progressive increase to NaCl in the medium, for this seedlins of tomato plants (Solanum lycopersicum L. Cv. Amalia) were submitted to seven different treatments: control (C) plants were maintained in nutrient solution without NaCl; adapted plants (PC) were submitted to progressive increase of 25 mM of NaCl each four days in nutritious solution, in the others treatments were submitted to 25, 50, 75, 100 and 125 mM of NaCl during all experimental period. The inhibition of dry mass accumulation in root system and stem was observed in non adapted plants, while the leaf dry mass and leaf area were affected in all treatments in relation to control plants. Saline stress decreased net photosynthetic rate, stomatal conductance and root hydraulic conductivity in non adapted plants, however, PC plants showed good osmotic adjustment, which enabled them to maintain leaf pressure potential, decreased leaf water potential and osmotic potential at full turgor while the biologic activity was appropriate. [ABSTRACT FROM AUTHOR]

In order to study the ecophysiological relations that affect the growth of B. decumbens in monocrop (MO) and associated withZ. leucocephala (AS), evaluations of photosynthetic active radiation (PAR), assimilation (A) stomatic conductance (Gs), transpiration (E), relative humidity (RH), water potential (0h), differential of steam pressure (DSP) and leaf area index (LAI) were made in a tropical humid forest zone. The evaluations were made 5,10 and 22 days after grazing under both conditions (MO and AS). The most positive values of 0h (P<0,05) were found in AS, as well as the lowest values of PAR (P<0,05) in all the evaluated dates. RH and DSP did not show differences (P 0,05). The gas exchange parameters (E, Gs and A) showed significantly higher values in MO (P<0,05) in all dates. LAI was higher in MO after 10 and 22 days of evaluation. Due to the limitation of the photosynthetic capacity exerted by the light decrease on the grass, that PAR is concluded to be the most important factor that determine growth and development of B. decumbens in AS. [ABSTRACT FROM AUTHOR]

The physiological response of tomato crop (Lycopersicon esculentum) cv INCA 9 (1) was studied after applying two inoculant forms made up of Glomus sp1 (INCAM 4): one in a solid medium and the other in a liquid medium. The solid inoculant was directly put in the substrate of the pots at a single dose and time, whereas the liquid inoculant was sprayed by means of drop irrigation system at different doses and times. The experiment was carried out in a cooling-equipped polycarbonate greenhouse for temperature and relative humidity control. Results showed that the highest colonization and fungal occupation percentages were reached 40 days after seed germination in the liquid inoculant treatments. Soil moisture values were similar in all treatments, indicating that an adequate irrigation regime was supplied to plants, in order to guarantee the same water requirements during all the experimental period. In general, the values of water relations, gas exchange, dry biomass growth and morphological growth variables were higher when plants were treated with the liquid inoculant through irrigation, independently of the dose and time used. [ABSTRACT FROM AUTHOR]

This research work was aimed at determining the effect of high temperatures on some growth variables and gas exchange in tomato plants of Amalia cv. Plants were grown in pots containing silica sand, which were put in trays adding Hoagland's nutrient solution to them. Treatments consisted of a control having a temperature of 25 gC during the day and 18 gC in the dark period, another treatment in which day and night temperatures increased 5 gC every four days up to 40 with 33 gC and a variant where plants were subjected to a heat shock of 40/33 gC day/night respectively for a period of four days. Once treatment application was concluded, plants were placed under the same conditions of the control treatment for 12 days, to evaluate their recovery. Evaluations on biomass, stomatal conductance and CO2 assimilation rate were recorded at the end of every period of heat treatment and recovery. Data analysis made evident a depressive effect of different variables evaluated when increasing environmental temperature; such effect was not eliminated in some indicators after the recovery period. [ABSTRACT FROM AUTHOR]