Key message
Progressive drought induced a gradual increase in non-structural carbohydrates in roots and leaves, slowing the drop in water status. The roots had an increase of 95 % compared to ...well-watered plants, while the leaves only increased by 21 %. Since
Cenostigma pyramidale
is a deciduous species, the non-structural carbohydrates are mainly found in the roots, which helps the plant survive the intense drought period.
The ability to produce and control the distribution of non-structural carbohydrates (NSC) may be critical to the success of deciduous woody plants from seasonally dry tropical forests. Thus, our aim was to investigate how carbohydrate allocation occurs and the dynamics of water status during the pre-senescence leaf period. We performed a controlled experiment on progressive drought stress using
Cenostigma pyramidale
, and found that leaf relative water content decreased only under severe drought conditions (SVD), when soil water content was approximately 5%, three times less than well-hydrated plants, and foliar relative water content (RWC) was close to 35%. Gas exchange was maintained at a high level until the moderate drought stage (MD), with soil water content and RWC of 8% and 75%, respectively. Prior to leaf senescence,
C. pyramidale
maintained the net CO
2
assimilation and intense production of NSC, which were stored mainly in the leaves (45%), and roots (44%), with only 11% in the stems. This increase in root NSC content during progressive drought levels suggests that this tissue may be the main storage site for NSC, which could allow the plant to survive the dry season, and also have reserves for leaf sprouting at the beginning of the next rainy season. The results suggest that studies involving carbon metabolism in woody species under stress should consider root tissue, as this is an important source of NSC during drought.
The evergreen C3 plant Calotropis procera is native to arid environments. Thus, it grows under high vapor pressure deficit (VPD), intense light, and severe drought conditions. We measured several ...ecophysiological traits in C. procera plants growing in semi-arid and seacoast environments to assess the attributes that support its photosynthetic performance under these contrasting conditions. Gas exchange analysis, primary metabolism content, nutrients, the antioxidant system, and leaf anatomy traits were measured under field conditions. In the semi-arid environment, C. procera was exposed to a prolonged drought season with a negative soil water balance during the 2 years of the study. Calotropis procera plants were exposed to a positive soil water balance only in the rainy season in the seacoast environment. The leaves of C. procera showed the same photosynthetic rate under high or low VPD, even in dry seasons with a negative soil water balance. Photosynthetic pigments, leaf sugar content, and the activity of antioxidant enzymes were increased in both places in the dry season. However, the anatomical adjustments were contrasting: while, in the semi-arid environment, mesophyll thickness increased in the driest year, in the seacoast environment, the cuticle thickness and trichome density were increased. The ability to maintain photosynthetic performance through the seasons would be supported by new leaves with different morpho-anatomical traits, with contrasting changes between semi-arid and seacoast environments. Furthermore, our results suggest that an efficient antioxidative system and leaf sugar dynamics can contribute to protecting the photosynthetic machinery even under severe drought.
The effects of drought stress and leaf phosphorus (Pi) supply on photosynthetic metabolism in woody tropical species are not known, and given the recent global environmental change models that ...forecast lower precipitation rates and periods of prolonged drought in tropical areas, this type of study is increasingly important. The effects of controlled drought stress and Pi supply on potted young plants of two woody species, Anadenanthera colubrina (native) and Prosopis juliflora (invasive), were determined by analyzing leaf photosynthetic metabolism, biochemical properties and water potential. In the maximum stress, both species showed higher leaf water potential (Ψl) in the treatment drought +Pi when compared with the respective control −Pi. The native species showed higher gas exchange under drought +Pi than under drought –Pi conditions, while the invasive species showed the same values between drought +Pi and −Pi. Drought affected the photochemical part of photosynthetic machinery more in the invasive species than in the native species. The invasive species showed higher leaf amino acid content and a lower leaf total protein content in both Pi treatments with drought. The two species showed different responses to the leaf Pi supply under water stress for several variables measured. In addition, the strong resilience of leaf gas exchange in the invasive species compared to the native species during the recovery period may be the result of higher efficiency of Pi use. The implications of this behavior for the success of this invasive species in semiarid environments are discussed.
•Invasive and native species from dry tropical forest.•Effects of drought and phosphorus supply on photosynthetic metabolism.•High foliar phosphorus content may alleviate photosynthetic rate.•Invasive and native are different in drought tolerance strategy.
ABSTRACT The effects of water deficit on physiological and biochemical variables of young plants of two tropical woody species, Pachira aquatica and Sterculia foetida, and their recovery abilities ...were measured. Leaf water potential, gas exchange and selected carbon metabolism components were measured in a greenhouse experiment with control, moderate and severe water deficit treatments. Under severe drought stress, gas exchange and chlorophyll fluorescence decreased in both species compared to their respective controls. After rehydration, P. aquatica and S. foetida showed a partial and full recovery of the measured variables, respectively. In addition, a decrease and an increase in photosynthetic pigments were observed for P. aquatica and S. foetida, respectively, compared to their controls. In conclusion, the two species showed differing responses regarding photosynthetic pigment content dynamics for tolerating water deficit. Individuals of P. aquatica in the severe water deficit treatment showed a decrease in pigments, which may have impaired the recovery of metabolism (gas exchange) after rehydration, while S. foetida experienced an increase, favoring a full recovery of gas exchange and biochemical metabolism after rehydration.
Cenostigma pyramidale
is a native legume of the Brazilian semiarid region which performs symbiotic association with arbuscular mycorrhizal fungi (AMF), being an excellent model for studying genes ...associated with tolerance against abiotic and biotic stresses. In RT-qPCR approach, the use of reference genes is mandatory to avoid incorrect interpretation of the relative expression. This study evaluated the stability of ten candidate reference genes (CRGs) from
C
.
pyramidale
root tissues under salt stress (three collection times) and associated with AMF (three different times of salinity). The
de novo
transcriptome was obtained via RNA-Seq sequencing. Three algorithms were used to calculate the stability of CRGs under different conditions: (i) global (Salt, Salt+AMF, AMF and Control, and collection times), (ii) only non-inoculated plants, and (iii) AMF (only inoculated plants).
HAG2
,
SAC1
,
aRP3
were the most stable CRGs for global and AMF assays, whereas
HAG2
,
SAC1
,
RHS1
were the best for salt stress assay. This CRGs were used to validate the relative expression of two up-regulated transcripts in Salt2h (
RAP2-3
and
PIN8
). Our study provides the first set of reference genes for
C
.
pyramidale
under salinity and AMF, supporting future researches on gene expression with this species.
ABSTRACT Studies addressing the physiological and anatomical responses of plants under different light intensities normally are performed in short term. Thus, the present study includes a long term ...analysis. This study aims to verify whether the phenotypic variability off attributes in two woody tropical specieis, Paquira aquatica and Sterculia foetida, are compatible both under short term exposure to different light availability levels (full-light and half-light local irradiance) and long-term exposure in the same conditions. The study was developed in two phases: phase I (short term) and phase II (long term). The variables measured were referent to CO2 assimilation responses to light intensity, chlorophyll a fluorescence, chlorophyll content, morpho-anatomical attributes and phenotypic variability. In phase I, P. aquatica had differences between treatments in Amax (maximum net photosynthesis) and LCP (light compensation point), without differences in these attributes in phase II. S. foetida plants had differences only in phase I in Amax. In anatomical attributes, P. aquatica had a higher palisade and spongy parenchyma and mesophyll thickness compared to S. foetida plants, without differences between light treatments. In S. foetida, the aforementioned cell layers were thicker in full-light treatment. Both species showed a higher phenotypic variability in the same physiological attributes in phase I and similar attributes for mesophyll thickness of the abaxial epidermis in phase II. The species showed different anatomical and physiological strategies, however with plastic responses in similar attributes, only observable after a longer period of exposure. The results indicated the importance of lengthy exposure to light, mainly in tropical species, wich are naturally exposed to elevated irradiance levels for an extended period of time in the field.
Exotic plants in semiarid region have developed strategies for efficient use or capture of resources. They have become invasive and outperform native species. To understand which factors could ...explain the success of invasive woody species in a semiarid region, several physiological traits were analyzed in young plants of two invasive and two native species exposed to different water availability. Invasive plants showed low leaf construction cost, high phosphorus and nitrogen contents, reduced loss of instantaneous energy use efficiency, and smaller specific leaf area when compared to native species. This strategy led to a higher biomass gain and a high root/shoot ratio in both water treatments. After rehydration, invasive plants showed faster recovery and higher rates of CO2 assimilation. This resilience is fundamental for species in semiarid regions, and also increase uptake of nutrients. Maintaining a high photosynthetic rate, whenever there is water availability is a strategy that increases the performance of the species in relation to biomass gain. The low leaf construction cost and the fast recovery of the photosynthetic metabolism of invasive plants after limiting water resources explains the success of these species, and suggests that their potential may increase under prolonged and severe drought seasons.
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•Native and invasive semiarid woody species under different water regime.•Under drought invasive species has different behavior than native.•The performance of nutrients uptake is greater in invasive.•Invasive lost their low cost leaves under drought, and sprouted new after rehydration.•The highest root biomass was of invasive species when well-watered and drought stress.
This study aimed to evaluate the leaf primary metabolism in two woody species, Sterculia foetida and Bombacopsis glabra. Both species have seeds rich in oil and they are largely found in regions with ...irregularities in water availability. Seedlings were grown in a greenhouse from seeds. At 140 days after emergence, 50% of the plants were subjected to salt stress for 23 days, daily receiving 100 mM of NaCl solution. In both species, leaf stomata conductance and water potential decreased quickly under salt stress. The two species showed different strategies in photosynthetic pigment concentration and components of nitrogen metabolism. S. foetida kept the pigment concentration unchanged after 23 days of stress, while B. glabra increased concentration of chlorophyll a and carotenoids. S. foetida showed a high leaf concentration of K+ in stressed plants and a Na+/K+ ratio without differences when compared to control. Thus, S. foetida presented a better ionic balance, while B. glabra invested in photoprotection. Therefore, both species present potential to be planted in Brazilian Northeast, where water deficit and salt stress are challenging for annual crops.
Basic mechanisms are known to promote salt tolerance in plants: a delay in Na+ uptake or rapid Na+ remobilization from leaf tissue. We measured dynamics of the Na+/K+ ratio and components of carbon ...metabolism during the first 72 h after saline stress (200 mM NaCl) began in Cenostigma pyramidale, a woody species, under controlled conditions. Saline stress at two times: one plant group at the beginning of the morning and the other in the evening. Stressed plants had three times more Na+ in leaves than did control plants in the first 24 h. However, in the next few hours, despite new applications of saline solution, the Na+/K+ ratio continued to decline. Several samples, including night treatments, provided evidence that this species uses Na+ recirculation mechanisms to endure salt stress. Effects of salt on the traits evaluated differed depending on the time when stress began. Between the two saline treatments, in the first 24 h after saline stress, gas exchange decreased more strongly in morning-stressed plants, when large amounts of Na+ reached the leaf and K+ left this organ. Nevertheless, when stress was applied in the evening, leaf Na+ remobilization was faster, and the soluble sugar/starch ratio remained greater than did the control. Our data suggested that time of the beginning of salt stress could change the level of damage. Morning-stressed plants synthesized greater amounts of proline, H2O2, and malondialdehyde than did night-stressed plants. We recommend that details regarding the time of stress be taken into consideration in physiological studies.
•A woody species was subjected to salt stress.•Saline stress changed the species response depending on the time of day it is applied.•The leaves decreased Na+ and recovered K+ concentration quickly.•This woody species prioritized increase soluble sugar/starch ratio under stress.•Proteins and proline content were kept under stress.
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