XII CONGRESSO DE ECOLOGIA DO BRASIL
PHYSIOLOGICAL RESPONSE OF A SUBSHRUB SPECIES TO
SUCCESSIONAL STAGE AND VAPOR PRESSURE DEFICIT
IN A TROPICAL DRY FOREST
Hiram Marinho Falcão – Federal University of Pernambuco, Department of Botany, Recife, PE.
[email protected].
Vanessa Andrade de Barros - Federal University of Pernambuco, Department of Botany, Recife, PE.
Camila Dias Medeiros - Federal University of Pernambuco, Department of Botany, Recife, PE. Jarcilene Silva de
Almeida-Cortez - Federal University of Pernambuco, Department of Botany, Recife, PE.
Mauro Guida dos Santos - Federal University of Pernambuco, Department of Botany, Recife, PE.
INTRODUCTION
The ability to modify the patterns of response of functional attributes due to changes in the environment is crucial
for success in plant populations establishment. Environments that have different abiotic characteristics, such as
areas at different stages of natural regeneration, provide the plant populations favorable scenarios to variation in
their functional attributes (Zhu et al. 2013). According to Cabral et al. (2013), more than 80% of Brazilian Tropical
Dry Forests are successional, forming mosaics of areas in different stages of regeneration. In a functional
perspective, attributes related to photosynthetic capacity and water uptake respond to differences found in different
stages of regeneration. Pioneer plants had higher photosynthetic rates, and hence faster growth than plants of late
stages (Poorter and Bongers, 2006). However, some pioneer species can settle in areas in other successional stages,
showing high phenotypic plasticity. Thus, analyze how key leaf traits vary in time and space is important to
understand the process of ecological succession.
OBJECTIVE
The aim of the study was to assess whether gas exchange and water potential of a subshrub species vary according
to the successional stage where it is established, and the variation in vapor pressure deficit (VPD) in a dry tropical
forest.
METODOLOGY
Study Site
The study was conducted at Tamanduá Farm, in the municipality of Santa Terezinha, Paraíba, Brazil. The
measurements were carried out in a chronosequence of two successional stages, early and late, defined according to
the structure of the plant community and the areas history of usage (Freitas et al., 2012). The species selected for
this study was Sida galheirensis Ulbr. (Malvaceae), a subshrub, annual, and that is found in both successional
stages.
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XII CONGRESSO DE ECOLOGIA DO BRASIL
Field Measurments
The VPD showed mean values ??of 0.25 kPa in the morning (low VPD) and 2.6 kPa in the afternoon (high VPD).
The water status was determined by leaf water potential (Scholander et al. 1964), both in the predawn as at 13:00h.
Gas exchanges were obtained by an Infra-Red Gas Analyzer (LCi, ADC Bioscientific, Hoddeston, UK) at 08:00h
and 13:00h, which were measured stomatal conductance (gs), the maximum CO2 net assimilation (Amax), and the
water use efficiency (WUE). For data comparison, a factorial ANOVA was performed, followed by the test Student
Newman Keul's at a 5% probability when necessary.
RESULTS
The leaf water potential did not vary among successional stages (P > 0.05). However, the water potential was on
average 2.7-fold lower in the afternoon than in the predawn, in both successional stages (P < 0.05). The stomatal
conductance did not vary even between low and high VPD, or among successional stage (P > 0.05). The CO2
assimilation was 16% higher in the early successional stage in the morning compared to late stage (P < 0.05), with
no difference in the high VPD period. Plants of late successional stage had water use efficiency 10% higher in low
VPD period (P < 0.05), followed by early stage. There was no significant difference between the stages in the
afternoon. However, the values ??were on average 2-fold lower than in the morning (P < 0.05).
DISCUSSION
The results show that S. galheirensis has greater carbon assimilation in the
early successional area, which is expected for a pioneer plant (Navas et al.
2010). However, the efficient stomatal control, which keeps the stomata open
at high VPD, allows this species presents high gas exchange rates, even with
a significant drop in water potential in the afternoon. Although the water
potential is lower at high VPD, the values ??are still high compared to other
plants of semiarid environments, even in the predawn (Kizito et al. 2012).
This can be evidenced by the low water use efficiency at high VPD, which in
turn also contributes to maintain the photosynthetic rates.
CONCLUSION
The species Sida galheirensis Ulbr. can maintain its photosynthetic performance during the natural regeneration
process, showing acclimatization capacity to environments with different abiotic conditions.
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