Morphological and photosynthetic alterations in the Yellow-ipe, Tabebuia chrysotricha (Mart. Ex DC.) Standl., under nursery shading and gas exchange after being transferred to full sunlight

Abstract

The objective of this study was to evaluate the effect of nursery shading on the Yellow-ipe seedling (Tabebuia chrysotricha) growth, photosynthesis, and photosynthetic acclimation after being transferred into direct sunlight. The Yellow-ipe seedlings were grown under 0, 50, 70 and 95% shade. At the 134th day of sowing, leaf gas exchange and chlorophyll were measured under current growth shading, after exposure to 15 min and two day full sunlight. With the increase of shading, the Yellow-ipe seedlings allocated more biomass to the stem and leaves and less to the roots, and there was an increase in the leaf area ratio and specific leaf area. In relation to 0% of shading there was a increase of 211% in stem, 116% in leaf, and a reduction of 200% in roots biomass when seedling were grown under 95% of shading. The total biomass accumulation had a high correlation with collar diameter (r = 0.96). More than 70% of the shading reduced the photosynthesis, and after transferring the seedlings into full sunlight, more than 50% of the shading induced a reduction in chlorophyll, stomatal conductance, photosynthesis and instantaneous carboxylation efficiency, suggesting the presence of a photoinhibition process. The Yellow-ipe seedling growth under nursery conditions should not be done under more than 50% shading, which may result in the lower seedling quality and poorer acclimation to transplantation, particularly to severe degraded areas with direct sunlight. The species can be used for recovering from totally devastated forest areas to initial recovery when full canopy are forming.

Studies on Estimation of Leaf Gas Exchange of Ornamental Woody Plant Species

“…Several studies emphasized the importance of environmental conditions for leaf gas exchange. Endres et al (2009) found that light environment influence the CO 2 fixation. The correlation between PAR (photosynthetic active radiation) and photosynthetic rate of Tabebuia chrysotricha differs depending on light environment: the correlation was stronger (R 2 =0.6699) at plants grown under shade and lower (R 2 =0.29) at plants grown in sunlight.…”

“…1). The different PAR may greatly influence the photosynthetic activity of plants (Endres et al, 2009). These values were measured in a period from 12 am to 14 pm which means the highest radiation during the day.…”

Morphological and photosynthetic adaptations of Tabebuia aurea seedlings in the nursery

“…Changes in the number of leaves were not observed in Hymenaea parvifolia (Silva et al, 2007) under up to 70% shade at 105 days after planting, Simarouba amara Aubl under up to 70% shade at 182 days after germination (Azevedo et al, 2010) or Caesalpinia echinata Lam under up to 80% shade analysed at 12, 18 and 24 months after germination (Aguiar et al, 2005). Moreover, Fonseca et al (2002) found reductions in the number of leaves in Trema micrantha (L.) Blume grown under 48% shade at 120 days after germination, while Endres et al (2010) reported a significant increase in the number of leaves in Tabebuia chrysotricha, especially those grown under 70% shade at 130 days after planting.…”

“…However, in plants subjected to environments with more light, the leaf area is decreased, which is beneficial to the plant given that less leaf material is exposed to potential damages The dry mass allocation to the root system of T. aurea ranged from 13% (under 95% shade) to 24% (under full sunlight, Figure 3B). Silva et al (2007) and Endres et al (2010) observed reductions in the dry mass of the root systems of Hymenaea parvifolia and Tabebuia chrysotricha plants, respectively, under 70% shade, while Dantas et al (2009) observed no significant differences in the dry masses of roots in seedlings of Caesalpinia pyramidalis Tul. grown under 75% shade at 100 days after sowing.…”

“…Several native species have been used in shading studies, including many tropical tree species (Fonseca et al, 2002;Aguiar et al, 2005;Lima Jr. et al, 2006). However, little is known about the photosynthetic acclimation of seedlings grown in nurseries to reforestation areas (Aleric & Kirkman, 2005;Lima Jr. et al, 2005;Endres et al, 2010), and a significant photosynthetic depression can occur when seedlings acclimated to shade are suddenly exposed to full sunlight (Zhang et al, 2003).…”