Leaf Gas Exchange Characteristics of Four Papaya Genotypes During Different Stages of Development

Abstract

-In this research, was used four papaya (Carica papaya L.) genotypes: three from the 'Solo ( Sunrise Solo TJ, Sunrise Solo 72/12 and Baixinho de Santa Amália) group and one from the 'Formosa' group (Know-You 01). They were grown in plastic pots containing a sandy-clay-loam soil subjected to pH correction and fertilization, under greenhouse conditions. Throughout the experimental period plants were subjected to periodic irrigation to maintain the soil humitidy around field capacity. The experiment was conducted 73 days after sowing. In all genotypes, leaf gas exchange characteristics were determined. The net photosynthetic rate (A, µmol m folhas, contadas a partir do ápice, por meio de um analisador de gás no infravermelho modelo LI-6200. Entre as folhas amostradas e entre os genótipos estudados, não foram observadas diferenças significativas nos valores de A, g s, c i e T l . Foi observado que elevados valores de g s proporcionaram valores elevados de A em todos os genótipos estudados. Contudo, para a característica T l , as relações com g s foram inversas, evidenciando a fundamental função do processo transpiratório no resfriamento foliar. Os resultados indicaram que, em todos os genótipos estudados, as folhas avaliadas funcionaram como órgãos fontes.

Physiological aspects of sun and shade leaves of Lithraea molleoides (Vell.) Engl. (Anacardiaceae)

“…Leaf response to different light conditions vary widely among species (Rijkers et al, 2000). Overall, leaves growing under intense light display the following characteristics: higher mesophyll width, cuticule and photosynthetic rate (Campostrini et al, 2001;Avalos and Mulkey, 1999;Oguchi et al, 2003). The highest photosynthetic rate in leaves exposed to intense light is associated to important morphoanatomic adaptations, especially greater cuticle and palisade parenchyma thickness, which allow the plant to minimize water loss and transmit the excess of light more directly, under more xeric conditions of the upper portion of the tree crown (Selleck andShupert, 1957 apud Martinez andMedri, 1985) and to prevent photoinhibition (Lemos-Filho, 2000).…”

Gas exchange, phisiological indexes and ionic accumulation in Annona emarginata (Schltdl.) H. Rainer seedlings in nutrients solution

“…As regards photosynthetic responses, it must be emphasized that the access of the atmospheric CO 2 to the photosynthetic cells from the mesophyll occurs through stomatal opening and, therefore, variations in the stomatal conductance (g s ) directly affect A and E (ÁLVAREZ et al, 2011). In addition, g s is influenced by the environment (CAMPOSTRINI et al, 2010), abscisic acid (MAHOUACHI et al, 2006) and mineral nutrition (MARSCHNER, 2012). In plants grown under 100% I, transpiration rate (E) decreased ( Figure 3C), whereas A values were stable up to 98 DAT and decreased up to 126 DAT, similarly to A net /C i ( Figure 3B), which resulted in CO 2 accumulation in the leaves ( Figure 3F).…”

Constraints on the evolution of phenotypic plasticity in the clonal plant Hydrocotyle vulgaris

“…Moreover, the reduced transpiration rate may be the consequence of decreased moisture evaporation due to hampered gas exchange between the plant and the environment arising from stomatal closure (Mommer et al ., ; Ivancich et al ., ). In flood conditions, diminished photosynthetic processes may be caused not only by stomatal limitation, but also by adverse metabolic consequences of hypoxia, such as reduced Rubisco activity, disruptions in photosynthate transport and chlorophyll degeneration (Pezeshki et al ., ; Campostrini et al ., ; Nicotra et al ., ). When photosynthesis is impeded by flood, plant growth is dominated by respiration; as a consequence, soluble sugar content is consumed to produce energy (van Kleunen et al ., ; McDowell et al ., ; Bongers et al ., ).…”