Cladode Area Research Articles

Efeitos da Adubação e de Nematicida no Crescimento e na Produção da Palma Forrageira (Opuntia ficus indica Mill) cv. Gigante

O experimento foi realizado em telado do Departamento de Zootecnia da UFRPE, objetivando medir o efeito da adubação e de nematicida no crescimento e produção da palma, com sintoma de amarelecimento. Os tratamentos experimentais constaram da adição ou não de macronutrientes, micronutrientes e de nematicida em um delineamento experimental em blocos casualizados. Para número de cladódios primários, a análise de variância demonstrou efeito não significativo pelo teste F. Para número total de cladódios, número de cladódios secundários, área de cladódio, índice de área de cladódios e produção de matéria seca, a análise de variância revelou efeito significativo. Não houve efeito dos micronutrientes e de nematicida no grupo dos tratamentos de Solução de Macronutrientes Completa para número de cladódios primários, número de cladódios secundários, área de cladódio, índice de área de cladódios e produção de matéria seca, sendo a média geral 1,56; 0,84; 811,11 cm²; 1,15 e 42,73 g/vaso, respectivamente.

Diurnal and seasonal changes in cladode photosynthetic rate in relation to canopy age structure in the leguminous shrub Retama sphaerocarpa

1. Changes in canopy area and canopy age structure of the leguminous shrub Retama sphaerocarpa were estimated non‐destructively by monitoring growth and survivorship of cladodes on marked shoots. 2. Gas exchange of cladodes of different age classes was measured by infra‐red gas analysis during a period of 18 months. The effects of seasonal and year‐to‐year variation in the area and age structure of the canopy on daily carbon assimilation were assessed. 3. New canopy area produced by spring growth was highly variable between years and also affected the age structure of canopies because of differential survivorship of older cohorts of cladodes. 4. During the first year (1993), predawn water potential of cladodes and, therefore, their maximum diffusive conductance (0·35–0·45 mol m–2 s–1) and photosynthetic rate (20–26 μmol CO2 m–2 s–1), changed little with the season because the deep‐rooted shrubs had access to permanent water sources. Lack of rainfall in the winter of 1993/1994 constrained predawn water potential and rates of gas exchange in the following growing season when daily maxima of A declined continuously and fell to a minimum of 10 μmol CO2 m–2 s–1 in July 1994. 5. Nitrogen concentration and specific cladode area, but not nitrogen content, were significantly different between annual cohorts. Mainly as a result of secondary diameter increment of cladodes, specific cladode area and nitrogen concentration and therefore photosynthetic rate generally declined with increasing age of cladodes, but the differences in the photosynthetic rate between cohorts were insignificant during the cool season. 6. Variation in canopy area caused variation in daily carbon assimilation by 30–36% within years and by 37–52% between years. Seasonal and between‐year variation in the age structure of canopies, however, only accounted for changes in daily carbon assimilation of ± 2%. Canopy age structure thus appears to be an insignificant variable affecting carbon gain in R. sphaerocarpa.

Cladode development, environmental responses of CO2uptake, and productivity for Opuntia ficus-indica under elevated CO2

Opuntia ficus-indica, an extremely productive CAM plant cultivated in many countries, was exposed to 36, 52, and 72-73 Pa CO 2 in field plots and open-top chambers. Initiation of new cladodes (stem segments) was monitored until the canopy closed, after which bimonthly harvests maintained the plants for one year at a cladode area per unit ground area that is optimal for biomass production. Doubling the CO 2 partial pressure slightly increased the number of first-order daughter cladodes growing on the basal (planted) cladodes after 3 months and nearly doubled the number and area of second-order cladodes. When the CO 2 level was doubled, cladodes were 5% thicker after a few months and 11 to 16% thicker after one year