MORPHOPHYSIOLOGICAL AND NUTRITIONAL BEHAVIOR OF Hymenaea stigonocarpa Mart. ex Hayne (FABACEAE) SEEDLINGS SUBMITTED TO LIMING

Liming is benefi cial for plants as it promotes pH elevation, neutralization of toxic aluminum, increase in calcium (Ca2) and magnesium (Mg2) supply, and provides greater root systems. However, it is known that diff erent species, mainly those native to the Cerrado, respond in diff erent ways to this technique. Given the above, the objective of this study was to determine how Hymenaea stigonocarpa (“Jatobá-doCerrado”) seedlings respond to liming in Dystrophic Red Latosol. The plants were cultivated in four-liter pots, submitted to diff erent base saturation (natural soil, 30, 45, 60 and 75% V) and maintained in a greenhouse. Biometrics, biomass, nutritional content and physiological parameters were evaluated. A diff erence in Ca2 and Mg2 contents between leaves and stems was observed, leading to signifi cant reductions in stomatal conductance, transpiration, internal CO 2 concentration and internal and external CO 2 concentration ratios, resulting in a reduction of the investment in growth and biomass. Given these results, there is no need for liming in the production of H. stigonocarpa seedlings in a Dystrophic Red Latosol.


1.INTRODUCTION
Low fertility and nutrient availability, problems such as soil acidity and aluminum toxicity limit plant productivity, preventing plants from reaching their full potential (Rao et al., 2016). To correct these factors, liming is practiced. This technique aims to improve production potential by correcting soil acidity to obtain optimum yields. The soil acid/alkaline balance (as measured by pH) is very important in maintaining optimal soil nutrient availability and minimizing potential toxicities (Agegnehu et al., 2019). Liming increases base saturation and calcium and magnesium availability, while phosphorus and molybdenum fi xation which are reduced by the inactivation of reactive constituents and toxicity due to excess soluble aluminum, iron and manganese, is corrected, also promoting root growth and improving nutrient absorption (Agegnehu et al., 2019).
Several studies have applied this technique in the production of forest species seedlings. These studies indicate that species from diff erent ecological groups present positive to liming responses, and that this result is only obtained for plants classifi ed as pioneers and secondary species (Furtini Neto et al., 1999). However, some studies report no diff erence between pioneer and climax species (Macedo, 2008), and others demonstrate that liming did not promote diff erences even in pioneers, as in the case of Schizolobium parahyba (Vell.) S. F. Blake and Leucochloron incuriale (Vellozo) Barneby and Grimes (Coneglian et al., 2016;Santos et al., 2019). Liming promoted negative responses to seedling growth in Plathymenia foliolosa Benth and Dimorphandra mollis Benth (Freitas et al., 2017b;Cota et al., 2019), while positive response was noted in Dalbergia nigra (Vell.) Allemão ex Benth (Carlos et al., 2018). These results indicate that forest species may respond in diff erent ways.
Studies of this nature are scarce for some Cerrado species, and no information in the literature to help seedling producers is available. This is the case for Hymenaea stigonocarpa Mart ex Hayne from the Fabaceae botanical family, a medicinal species found in the Brazilian savannah, popularly known as "Jatobá-do-Cerrado" and widely used against general and respiratory pain (Fiebig and Pasa, 2018). H. stigonocarpa also produces high quality hard and sturdy wood (Moraes et al., 2018) and is also used in the recovery of degraded areas (Silva et al., 2014).
In nutritional terms, studies indicate that H. stigonocarpa responds to phosphate fertilization (Alves et al., 2015) as well as agro-industrial waste (Mizobata et al., 2016). However, no research demonstrating liming eff ects on H. stigonocarpa seedling production is available. Given the above, the aim of this study was to determine how H. stigonocarpa seedlings respond to elevation base saturation (liming) in a Dystrophic Red Latosol.
Plants were grown in four-liter pots and the experimental design was completely randomized, consisting of fi ve treatments (natural soil, 30, 45, 60 and 75% de V) and four repetitions each, totaling 20 experimental units. The Raij (1981) methodology was used to raise the soil base saturation to the levels of interest. The corrective agents calcium carbonate (CaCO 3 ) and magnesium carbonate (MgCO 3 ) were used at a 4: 1 ratio (Freitas et al., 2017a) and incorporated individually into the pots. H. stigonocarpa seeds were manually scarifi ed according to Santos (2011) and two were placed in each pot. After germination, thinning was performed leaving only one plant per pot. Planting occurred after 20 days of incubation in potted soil. The soil was maintained at 60% of fi eld capacity according to the International Association of Engineering Geology (IAEG, 1979).

Biometric and biomass assessments
Biometric evaluations consisted of plant height (H) obtained with a millimeter ruler, taking as default the apical meristem (Delarmelina et al., 2014) and stem diameter (SD) measured with a digital caliper. The total number of expanded leaves (NL) was also counted.
Using photographic records of the leaves of each experimental unit, the leaf area (LA) was calculated using The Image J Software (Research Services Branch, National Institute of Mental Health, Bethesda, Maryland, USA). With the leaf area and leaf dry mass (LDM) data, the specifi c leaf area (SFA) was calculated using the formula proposed by Barbieri Junior et al. (2007): SFA= LA/LDM. The plants were cut into leaves, stems and root and washed in distilled water. After separation of the vegetative organs, they were maintained in a forced air circulation oven at 65 ºC until constant weight. Subsequently, the leaf dry mass (LDM), stem dry mass (SDM) and root dry mass (RDM) were obtained (Delarmelina et al., 2014).

Data analysis
The data were subjected to analysis of variance by the F test for all variables at a signifi cance level of 5% (p≤0.05). When diff erences were found between treatments, the regression analysis was used as function of base saturation levels for each signifi cant variable, through the SISVAR 5.3 statistical program (Ferreira, 2011).

Biometric and biomass results
Biometric and biomass variables were not signifi cantly aff ected by increased base saturation. However, both decreased with increasing base saturation ( Figure 1A, C, D, E, F, G and H), except for stem diameter. The treatment resulting in the highest growth and biomass was the no liming (12%). The highest increase in stem diameter was observed at the highest base saturation (75%) ( Figure 1B).

Nutritional Content
A diff erence between treatments was noted for nutritional content. Increased base saturation led to increased Ca² + and Mg² + content in both H. stigonocarpa seedling leaves (Figure 2A and C) and stems ( Figure 2B and D). The data fi t an increasing linear model, where the higher base saturation (75%) allowed for greater Ca² + and Mg² + translocation to leaves and stems.

Gas exchanges
All physiological H. stigonocarpa seedling parameters were reduced with increasing base saturation. Diff erences were found between treatments for transpiration, stomatal conductance, internal CO 2 concentration internal and external CO 2 ratios ( Figure 3). The obtained data for these variables fi t a decreasing linear model (Figure 3). The highest values found for physiological variables were 11.3 for A; 0.15 for gs; 2.6 for E; 274.8 for Ci; 0.68 for Ci/Ca and 104.5 for ETR, all promoted in the non-liming treatment (12%).

4.DISCUSSION
The increases base saturation did not infl uence H. stigonocarpa seedling growth and biomass Although no diff erence in growth and biomass was noted, a diff erence in Ca² + and Mg² + content in both H. stigonocarpa seedling leaves and stems was observed. This is due to the fact that liming increases the availability of these nutrients in soil. However, this technique seems to be advantageous only for fast-growing species, as slow-growing species may absorb and translocate these nutrients, but do not use them as effi ciently. Thus, liming under the conditions of this study for H. stigonocarpa seedlings is characterized as a waste, since no responses in terms of growth due to increased base saturation in Dystrophic Red Latosol were observed. This is not uncommon, as several Cerrado species, such as Astronium fraxinifolium Schott, Guazuma ulmifolia Lam, Anadenanthera macrocarpa (Benth.) Brenan, Inga edulis Mart (Silva et al., 2011) and L. incuriale (Santos et al., 2019) have displayed the same behavior in relation to liming.
Even considering that liming is unnecessary under the studied conditions, the nutritional requirement of seedlings in other soil types may be diff erent. For example, Bernardino et al. (2005), Souza et al. (2008) and Souza et al. (2010) observed no signifi cant eff ect under increased base saturation elevation on the morphological characteristics of A. macrocarpa, Machaerium nictitans (Vell.) Benth and Senna macranthera (DC. Ex Collad.) HS Irwin and Barneby seedlings when grown in Argisol, while a signifi cant response was noted when these same species were cultivated in dystrophic Alatosol.
The increased Ca² + and Mg² + content in leaves and stems inversely aff ected stomatal conductance, transpiration, internal CO 2 concentrations and the relationship between internal and external CO 2 concentration in H. stigonocarpa seedlings. With reduced stomatal conductance, both transpiration and internal CO 2 concentration become limited. This aff ects other physiological parameters such as internal and external CO 2 concentration ratios and, mainly, photosynthesis. In addition, decreased gas exchanges lead to growth, development and seedling quality compromises, as these factors are related (Taiz and Zeiger, 2013).
The behavior noted in the seedlings as a function of liming indicates the possibility of toxicity. According to White and Broadley (2003), excess Ca² + in soil can lead to toxicity and reduced plant growth. Rothwell and Dodd (2014) observed leaf area reduction, gs, A and shoot biomass of two Fabaceae family species as a function of liming. The authors state that an alternative signal transmitted by the xylem decreases the stomatal conductance and gas exchange of the assessed species.
Liming eff ects on three Fabaceae family species studied by Rothwell et al. (2015) were similar to those observed in the present study, with no diff erences in nutritional contents, except for Ca² + . In addition, the authors also observed decreased gs, Ci, A and biomass accumulation. The authors attributed this behavior to increased Abscisic Acid (ABA) as a result of liming. Liming decreases water potential, resulting in increased ABA, which in turn decreases plant transpiration through stomatal closure, limiting CO 2 absorption and leading to low internal CO 2 concentrations, interfering with photosynthesis and, thus, resulting in decreased biometric parameters and biomass (Rothwell et al., 2015), as in observed herein.
Given this information, it is noted that some plants grow well at low soil Ca² + concentrations and respond very little when the availability of this nutrient increases, in some cases leading to growth inhibition, as observed in P. foliolosa and D. mollis (Freitas et al., 2017b;Cota et al., 2019). This is due to the fact that excessive Ca² + absorption in plants leads to ionic balance disturbances, decreased absorption of other nutrients or changes in cytosol pH (Balakrishnan et al., 2000).

5.CONCLUSIONS
Hymenaea stigonocarpa seedlings respond negatively to base saturation increases in Dystrophic Red Latosol, indicating no need for liming for seedling production.

ACKNOWLEDGMENTS
The authors thank the Coordination for the Improvement of Higher Education Personnel (CAPES) and the Federal Institute of Goiano (IFGoiano), Rio Verde.