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Lettuce is the most important leaf vegetable grown in Argentina mainly in the green belts. This species requires 90 to 100 kg ha-1 nitrogen, which can be supplied by synthetic chemical fertilizers or organic supplements. The objective of this work was to evaluate the effect of the application of vermicompost on the growth parameters of lettuce in two commercial types: leaf lettuce (cv Brisa) and butterhead (cv Daguan). Seedlings were produced in plastic trays and were transplanted when two leaves were completed expanded 30 days after sowing after that management was similar to a commercial one. The experimental design was a randomized complete block with four replications. During cultivation and at harvest measurements of fresh and dry weight, leaf number and area, nitrate and reducing sugar concentrations were made. Calculations for yield were performed. At harvest, vermicompost addition affected nitrate content in leaf lettuce (cv Brisa) increasing its concentration. Yield was not affected by vermicompost application.

Chlorophyll content of butterhead lettuce leaves was estimated by correlations between the Minolta SPAD-502 and Minolta chroma meter CR 300. The SPAD-502 readings and extractable chlorophyll (Chl a, Chl b, and total Chlorophyll) contents were related. High linear correlations were obtained for chlorophyll a (R2=0.90), chlorophyll b (R2=0.85), and total chlorophyll (R2=0.92). After that, during the growth cycle of butterhead lettuce grown in soilless culture, leaves were selected and SPAD-502 and chroma meter readings were made. Finally, correlations between SPAD-502 readings and leaf color (L*, a*, b*, C*, and hue angle) determined by the chroma meter were calculated. Hue angle (H°; R2=0.75) and lightness index (L*; R2=0.68) were the parameters that better relate with SPAD-502 readings, so these parameters can also be used for rapid and nondestructive estimates of leaf chlorophyll in situ. [ABSTRACT FROM AUTHOR]

Cone serotiny refers to canopy seed storage in cones that remain alive, though closed, for several years. There are some Cupressus species which have only serotinous cones, or both serotinous and non-serotinous cones on the same tree. Scale separation and seed release occurs immediately after the cone ripens in non-serotinous cones, or else the cones remain closed and alive longer, generally up to 15-20 years. Germination tests were done with serotinous cone seeds from C. arizonica Greene, C. benthamii Endl., C. lusitanica Mill., and C. macrocarpa Hartw. Germination was below 50% for all species. The highest levels of germination were obtained from 2- to 7-year-old cones, depending on the species. Cupressus arizonica showed a regular decline in germination values, from 43.5% for seeds from 3-year-old cones to 7.5% for seeds from 7-year-old cones. Cupressus benthamii had a maximum germination value of seeds from 5-year-old cones. Cupressus macrocarpa had a maximum germination capacity of 20.5% for seeds from 6-year-old cones, and it showed 7.5% germination for 12-year-old seeds. Cupressus lusitanica reached 33.5% germination of seeds from 5-year-old cones. Serotinous cones from Cupressus species, usually not collected because it is assumed that their seeds are not viable, can be utilized in cone harvesting, increasing the yield of the cone-bearing trees. [ABSTRACT FROM AUTHOR]