Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

Physiological and anatomical responses of

Passiflora tripartita var. mollissima (Passifloraceae) in water deficit

Gabriela Toro-Tobón1; https://orcid.org/0000-0002-7208-1028

Fagua Alvarez-Flórez*1; https://orcid.org/0000-0001-8897-2047

Hernán D. Mariño-Blanco1

Luz M. Melgarejo1; https://orcid.org/0000-0003-3148-1911

1. Laboratorio de Fisiología y Bioquímica Vegetal, Departamento de Biología, Facultad de Ciencias, Universidad

Nacional de Colombia Sede Bogotá, Carrera 45 #26-85, Bogotá, 111321, Colombia; gtorot@unal.edu.co, falvarez@unal.

edu.co (*Correspondence), hmarino@unal.edu.co, lmmelgarejom@unal.edu.co

Received 17-IX-2023. Corrected 01-II-2024. Accepted 08-VII-2024.

ABSTRACT

Introduction: Passiflora tripartita var. mollissima (banana passionfruit) is one of the most promising exotic tropi-

cal fruits from the diversity of the Passifloraceae family in South America, because of its organoleptic properties

and antioxidant activity.

Objective: To evaluate the physiological and anatomical responses of banana passionfruit plants under water

deficit to better understand the mechanisms that mitigate this stress and affect the production of crops subject

to climate change and global warming.

Methods: Three-month-old seedlings of banana passionfruit were subjected to a soil water deficit through an

irrigation reduction at 70 % for 49 days under greenhouse conditions. Morphology (leaf area, height, and number

of leaves) and physiological (stomatal conductance, Fv/Fm, total chlorophyll content) measurements were made

through time, and after the irrigation treatments were measured biomass parameters and anatomical foliar traits.

Results: The plants experienced a decrease in height, leaf area, number of leaves, leaf area index, and relative

water content, that are common responses in plants subjected to reduced irrigation. Additionally, the plants

exhibited certain mechanisms that can be attributed to water deficit tolerance such as higher root:shoot ratio,

stomatal closing, an increase in stomatal density, a reduction in mesophyll tissue thickness, and a decrease in the

number of vessels and its diameter as they enable the banana passionfruit to reduce water loss and decrease the

probability of cavitation in xylem vessels.

Conclusions: banana passionfruit plants could implement strategies against water scarcity, allowing them to

survive and endure challenging environmental conditions.

Key words: banana passionfruit plants; dehydration; morphology; physiology traits; leaf tissues.

RESUMEN

Respuestas fisiológicas y anatómicas de Passiflora tripartita var. mollissima (Passifloraceae) al déficit

hídrico

Introducción: Passiflora tripartita var. mollissima (banana passionfruit - curuba) es una de las frutas tropicales

exóticas de la diversidad de la familia Passifloraceae en Sudamérica, promisoria por sus propiedades organolép-

ticas y actividad antioxidante.

https://doi.org/10.15517/rev.biol.trop..v72i1.56532

BOTANY

2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

INTRODUCTION

The banana passionfruit plants (Passiflora

tripartita var. mollissima) produce fruits with

high export potential because of its organolep-

tic and nutritional properties, and high con-

tent of bioactive agents, antioxidants, phenolic

compounds, carotenoids and fiber (Fischer et

al., 2020; Flechas-Bejarano et al., 2019). It

is a species in the Tacsonia subgenus in the

Passifloraceae family, native to the Andean

region from Bolivia to Venezuela, that grows

in tropical and subtropical areas (Esquerre-

Ibañez et al., 2014; Primot et al., 2005). In 2022,

Colombia experienced a 25 % surge in banana

passionfruit exports to European countries,

making it the fourth most exported passion

fruit. Nationally, the supply reached 14 365

tons, with Boyacá contributing a significant

78.39 % (DANE, 2023).

In general, the cultivation of other pas-

sionfruit species has been increasing; however,

due to changes in climatic conditions, such as

high temperatures and low precipitation, crop

productivity is not satisfactory (Fischer et al.,

2009; Gomes et al., 2012). A decrease in water

availability produces a water deficit in plants,

altering growth, development, and production.

Drought resistance mechanisms in plants

can be classified as escape, avoidance, toler-

ance and recovery (dos Santos et al., 2022).

They may have escape responses, completing

their life cycle before the dry period begins

when phenological development successfully

fits with the availability of moisture in the soil

either by means of plasticity in development or

rapid phenological development (Farooq et al.,

2009). They may have avoidance mechanisms,

in which plants reduce the impact of drought

through morphophysiological changes that

minimize water loss, including stomatal con-

trol and root characteristics such as biomass,

length, density and depth, among others (dos

Santos et al., 2022; Farooq et al., 2009; Turner et

al., 1996). They may exhibit drought tolerance

mechanisms when plants could grow, repro-

duce, and provide an economic crop yield with

a poor water supply by means of adaptive char-

acteristics such as accumulation of compatible

solutes, increased response of the antioxidant

system and maintenance of water potential (dos

Santos et al., 2022; Farooq et al., 2009; Turner

et al., 1996).

Water deficits alter different processes, and

plant susceptibility depends on variables such

as genotype, state of development, duration,

Objetivo: Evaluar las respuestas fisiológicas y anatómicas de la curuba bajo déficit hídrico con el fin de compren-

der mejor los mecanismos que mitigan este estrés y afectan la producción de sus cultivos, que están sujetos al

cambio climático y al calentamiento global.

Métodos: Plántulas de 3 meses de edad se sometieron a un déficit hídrico mediante una reducción del riego al

70 % durante 49 días en condiciones de invernadero. Se realizaron mediciones morfológicas (área foliar, altura y

número de hojas) y fisiológicas (conductancia estomática, Fv/Fm, contenido de clorofilas) a lo largo del tiempo,

y transcurridos los tratamientos de irrigación se midieron parámetros de biomasa, además de rasgos anatómicos

foliares.

Resultados: Las plantas experimentaron una disminución en la altura, área foliar, número de hojas, índice de

área foliar y contenido relativo de agua, respuestas comunes en plantas sometidas a una irrigación reducida.

Adicionalmente, las plantas exhibieron ciertos mecanismos que pueden atribuirse a la tolerancia al déficit hídrico

tales como una mayor relación raíz:vástago, cierre de estomas, un aumento en la densidad estomática, una reduc-

ción en el grosor del tejido del mesófilo y una disminución en el número de vasos del xilema y su diámetro; pues le

permiten a la curuba disminuir la pérdida de agua y reducir la probabilidad de cavitación en los vasos del xilema.

Conclusiones: Las plantas de la curuba tienen la capacidad de implementar estrategias de mitigación frente al

déficit hídrico, lo que les permite sobrevivir y soportar condiciones ambientales desafiantes.

Palabras clave: curuba; deshidratación; morfología; caracteres fisiológicos; tejidos foliares.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

and intensity of stress. The latter may vary

depending on soil, climatic and agronomic fac-

tors (Anjum et al., 2011). The effects of a water

deficit on cultivated species have been studied

by several authors, where changes in growth

and development were observed (Anjum et

al., 2017), along with anatomical (Bacelar et

al., 2003; Choat et al., 2003), and physiological

responses that mainly affected stomatal con-

ductance, CO2 fixation, photosynthetic rate,

chlorophyll concentration and water status

(Basu et al., 2016; Ben Abdallah et al., 2018;

Boughalleb et al., 2014; de Freitas et al., 2017).

Although some studies have been carried

out on Passiflora tripartita var. mollissima for

responses of plant growth under different con-

ditions, for fruit quality and for post-harvest

treatments (Fischer & Miranda, 2021; Flechas-

Bejarano et al., 2019; Mayorga et al., 2020;

Rodríguez et al., 2019a; Téllez et al., 2011), the

effects of a water deficit on anatomy and physi-

ology are not known. It has been reported that,

under a water deficit, other Passiflora species

experience a reduction in growth, dry biomass,

and root vitality (Qi et al., 2023); a decrease

in physiological parameters such as leaf area,

stomatal conductance (Lozano-Montaña et al.,

2021), and a diminution in some chlorophyll

fluorescence parameters (Gomes et al., 2012).

Additionally, changes due to water deficit at

the anatomical level have been demonstrated in

tissues of the leaf blade (Gutiérrez et al., 2009;

Souza et al., 2018) and root (Lima et al., 2019),

and at the molecular level with gene families

involve in drought stress (Rizwan et al., 2022;

Yang et al., 2022).

Since a water deficit is one of the greater

constraints limiting agriculture productiv-

ity and profitability worldwide (Farooq et al.,

2009), information on the strategies used by

plants in response to water availability is essen-

tial to develop crops that are more tolerant to

droughts and have good agricultural produc-

tion. The objective of this study was to analyze

some physiological and anatomical responses

of banana passionfruit plants to water deficit.

MATERIALS AND METHODS

Growing conditions and biological mate-

rial: This experiment was conducted under

greenhouse conditions (4°38’08’’ N & 74°04’58’’

W, at 2 640 m.a.s.l.) at the Departamento

de Biología of the Universidad Nacional de

Colombia, Bogotá. Data on environmental con-

ditions during the experiment were collected

with a weather station (EM50 Data Logger

Decagon Devices Inc., Washington, USA). An

average ambient relative humidity of 74.04 %,

air temperature of 16.67 ºC, photosynthetically

active radiation of 169.04 μmol photons m-²

and photoperiod of 12 light h:12 h of darkness

were recorded.

Three-month-old Passiflora tripartita

var. mollissima plants, from Sabaneta village,

municipality of La Vega, in the department of

Cundinamarca, with 11 leaves and 6 tendrils,

were transplanted into pots (20x15 cm), with

a soil substrate (loamy texture: 30 % sand, 52

% silt, 18 % clay; pH 5.6) and rice husks at a

3:1 ratio. The seedlings were acclimatized for 1

month, keeping them under optimal conditions

for health, water and nutrients, after which

two irrigation treatments were carried out: (1)

Irrigated treatment at field capacity (Control

treatment) and (2) treatment for water deficit at

70 % water reduction (Water deficit treatment).

The requirements to reach field capacity for

the substrate were gravimetrically calculated to

determine the percentage of water used, along

with the amount of water to be added to the

70 % reduction treatment (water deficit). The

respective irrigation to maintain the water con-

ditions of each treatment was carried out every

third day. The experiment was monitored for

50 days.

Growth: The height of the stem was mea-

sured weekly from the base to the last node,

and the number of leaves and leaf area were

determined. The measurements were taken on

days 0, 7, 14, 21, 28, 35, 42 and 49 after the start

of treatment-dat. The leaf area index (LAI) was

estimated as proposed by Gardner et al. (2013).

At the end of the experiment, the dry weight

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of the shoot (stem plus leaves) and roots was

determined after drying the plants at 60 °C for

72 h (49 dat). Subsequently, the root: shoot ratio

(R/S) was determined.

Water status: The relative water content

(RWC) was determined with the methodology

described by Smart and Bingham (1974) with

foliar discs. This parameter was determined

at 49 dat with leaves from the middle-third of

three plants per treatment.

Stomatal conductance: This parameter

was determined with a porometer (Decagon

Devices, Inc., Washington, USA). Three leaves

from the middle-third of each plant were mea-

sured in seven plants for each treatment. This

measurement was taken from 08:30-10:00 AM,

selected with daily curves, on 0, 7, 14, 21, 28, 35,

42 and 49 dat. The data are shown as the aver-

age of seven plants per treatment along with the

standard error.

Photochemical efficiency of PSII (Fv/

Fm): The Fv/Fm was measured with a non-

modulated fluorometer (Pocket Pea-Hansatech,

UK). This measurement was taken at 5:00 AM

in 7 plants per treatment using one leaf per

plant, which were previously adapted to dark-

ness for 20 minutes on days 0, 7, 14, 21, 28, 35,

42 and 49 dat. The data are shown as the aver-

age of seven plants per treatment along with the

standard error.

Chlorophyll content: Leaves with differ-

ent green color intensities were selected, and

this parameter was estimated in SPAD units

with a Minolta SPAD 502 (Konica Minolta

Sensig, Inc., Sakai, Osaka, Japan). Leaf discs

were extracted from the exact same location

as the SPAD measurement. The leaf discs were

immediately ground, and the chlorophyll was

extracted with acetone (Lichtenthaler 1987;

Melgarejo et al., 2010; Rodríguez et al., 2019b;).

A calibration curve was constructed to relate

the chlorophyll content of different coloring

shades leaves to cover the entire color spectrum

and SPAD units (Lozano-Montaña et al., 2021;

Parry et al., 2014). During the experiment,

the chlorophyll content was estimated with

the SPAD using leaves from the middle-third

in three leaves from 7 plants per treatment

each week (0, 7, 14, 21, 28, 35, 42 and 49 dat).

This measurement was taken on the same leaf

where stomatal conductance and Fv/Fm were

measured, and it was calculated as the average

of three readings. The SPAD data were inter-

polated in the calibration curve to calculate the

chlorophyll content.

Anatomical morphometrics: At the end

of the experiment (49 dat), three leaves were

collected from the middle-third of plants in

each treatment. The leaves were fixed in FAA

(formaldehyde: acetic acid: 70 % ethanol,

10:5:85), stored in 70 % ethanol, and treated

following the protocol of Toro-Tobón et al.

(2022). This involved standard methods of

dehydration using a clearing agent (Histoclear),

paraffin infiltration, sectioning with a rotary

microtome (820 Spencer, American Optical

Company, New York, USA), and attachment to

microscope slides. The slides were stained with

astra-blue and basic fuchsin and deposited.

They were analyzed and photographed using

a microscope Olympus BX50 with a Moti-

cam Pro 282B camera (Olympus Optical Co.,

Ltd, Tokyo, Japan), in the optical equipment

laboratory of the Departamento de Biología,

Universidad Nacional de Colombia. Digital

images were processed and edited with ImageJ

(Schneider et al., 2012).

The images were used to take measure-

ments in leaf cross-sections for the thickness

of the upper and lower epidermis, spongy and

palisade parenchyma, cuticle, outer diameter of

the central rib and xylem. In addition, the inter-

nal diameter of xylem vessels and the number

of vessels were measured. The measurements

were taken ImageJ (Schneider et al., 2012). 3

leaves per treatment were taken, and 10 cuts

were taken from each leaf for the variables

(N = 30).

Stomatal density: An epidermal impres-

sion was made by coating the leaf surface with

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nail varnish using 4 leaves for each treatment

(Melgarejo et al., 2010). The surface morphol-

ogy/anatomical characteristics were studied

using a light microscope, Olympus BX50 with

a Moticam Pro 282B camera (Olympus Opti-

cal Co., Ltd, Tokyo, Japan), and the stomatal

density was calculated with 5 optic fields at a

400 magnification.

Experiment design and data analysis:

Each treatment had a total of 20 plants, of

which 7 were used to measure physiologi-

cal variables (non-destructive methods) during

the experiment, and another 7 were used for

biomass measurements (destructive methods)

carried out 49 dat. Water status assessed in leaf

discs (3 plants per treatment), and anatomical

parameters were determined using leaves (3

plants per treatment), both at the experiment’s

end. The experiment was replicated once under

identical conditions and with the same number

of plants, yielding similar results.

For the statistical analysis, the measured

variables of both treatments were compared

over time using the Kruskal-Wallis test. When

there were significant differences in this test,

peer comparisons (‘t’ tests) were used. For the

variables of the destructive methods, a single

comparison was made with a student’s ‘t’ test.

Finally, a Pearson correlation matrix was per-

formed with all variables at the 49 dat. The sig-

nificance level for all tests was α = 0.05. Figures

were performed with Prism (GraphPad, 2023)

and statistical tests were performed with R (R

Core Team., 2021).

RESULTS

Foliar physiology and biochemistry: A

lower plant height was observed with the water

deficit than in the control plants starting at day

35 after treatments began (dat). The plants with

the water deficit presented a height of less than

38.5 % at day 49 with respect to the control

plants (Fig. 1A). Lower values for the number

of leaves and leaf area were also evidenced from

day 35 for the water deficit treatment (Fig. 1B,

Fig. 1C).

For the accumulation of biomass, the con-

trol plants obtained a greater dry weight of

shoot and roots than those subjected to the

water deficit (Table 1). Significant differences

were found between the treatments for the root:

shoot ratio (R/S) and leaf area index (LAI).

The plants with the water deficit conditions

had a higher R/S ratio and a lower LAI than

Fig. 1. Growth variables of Passiflora tripartita var.

mollissima plants under water deficit for 49 days. A. Plant

height, B. leaf area and C. number of leaves. Vertical bars

represent the standard error of the mean, N = 7. Asterisks

indicate significant differences between treatments (control

and water deficit), on each of the days (P ≤ 0.05).

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the control plants, with a difference of 42.2 %

and 82.9 %, respectively (Table 1). The relative

water content (RWC) in the water deficit plants

decreased, with a significant difference at 49 dat

(Table 1), with a reduction of 32.5 % as com-

pared to the control plants.

The maximum photochemical efficiency

of PSII (Fv/Fm) had significant differences

between the treatments only until 42 dat, with

values close to (0.81), suggesting that the plants

that were subjected to the water deficit did

not exhibit photoinhibition of photosynthesis

(Fig. 2A). The stomatal conductance was also

lower in the plants subject to water deficit. This

variable had a progressive decrease until day 49

dat, with a significant difference from the con-

trol from day 21 dat (Fig. 2B). No significant

differences between treatments were found for

the chlorophyll content although a decreasing

trend was observed in the plants subject to the

water deficit from 21 dat to 49 dat (Fig. 2C).

Foliar anatomy: A dorsiventral mesophyll

was evidenced in the cross section of the leaf

blade in both treatments (Fig. 3A, Fig. 3B), with

Table 1

Relative water content (RWC), leaf area index (LAI), shoot dry weight (SDW), root dry weight (RDW) and root: shoot ratio

(R/S), of Passiflora tripartita var. mollissima plants under two treatments (control and water deficit).

Variable Control Water Deficit Test P-value

RWC 96.684 65.295 Kruskal−Wallis 0.0495*

LAI 1.325 0.282 Kruskal−Wallis 0.001*

SDW(g) 6.130 3.090 Kruskal−Wallis 0.017*

RDW (g) 3.496 3.226 t−Test 0.723

R/S 0.598 1.035 t−Test 0.015*

* Asterisks indicate significant differences between treatments (P ≤ 0.05).

Fig. 2. Physiological and biochemical variables of Passiflora

tripartita var. mollissima plants under water deficit for 49

days. A. Maximum photochemical efficiency of PSII Fv/

Fm, B. stomatal conductance and C. total chlorophyll

content. Vertical bars represent the standard error of the

mean, N = 7. Asterisks indicate significant differences

between treatments (control and water deficit), on each of

the days (P ≤ 0.05).

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

a uniseriate epidermis and a single layer of pali-

sade parenchyma. The plants subjected to the

water deficit had spongy parenchyma cells that

were closer together (Fig. 3B) than in the plants

without water deficit (Fig. 3A). The evaluation

of the stomatal imprint on both sides of the

leaves showed that banana passionfruit plants

have hypostomatic leaves with anisocytic (three

cells with a similar size enclosing the guard

cells) and anomocytic stomata (five or more

cells enclosing the guard cells) (Fig. 3E, Fig. 3F).

The epidermal cells had sinuous anticlinal walls

in both the control plants and plants subject to

the water deficit (Fig. 3A, Fig. 3B).

In the anatomical variables of the lamina

and the leaf midrib (Fig. 3B, Fig. 3C, Table 2),

Fig. 3. A. C. and E. Anatomy of the Passiflora tripartita var. mollissima leaves under control, and B. D. and F. water deficit. A.

B. C. and D. optical microscopy, sections stained with basic fuchsin and astra blue. A. and B. foliar blade, C. and D. midrib,

and E. and F. abaxial side. (co: collenchyma; ep: epidermis; ph: phloem; pp: palisade parenchyma; sp: spongy parenchyma;

st: stomata; xy: xylem). Scale bars (A. B. E. and F.) = 100 µm; (C. and D.) = 300 µm.

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significant differences were found (P ≤ 0.05)

between the control plants and those subjected

to the water deficit. A decrease in the thickness

of the mesophyll and its tissues was observed

in the plants subject to water the deficit, except

for the lower epidermis. Similar results were

seen for the variables outer diameter of the

median rib, outer diameter of the xylem, pro-

portion of both outer diameters, and the num-

ber and internal diameter of the vessels, which

were lower in the plants with the water deficit

(Table 2). However, the stomatal density in

the plants with the water deficit was higher

(Table 2).

As depicted in the correlation matrix

(Fig. 4), positive correlations were observed

between growth variables and certain anatomi-

cal parameters associated with vascular tissue.

A negative correlation was identified between

the root: shoot ratio and leaf area, number of

leaves, stomatal conductance (gs), Fv/Fm, and

certain tissue measurements (mesophyll, pali-

sade parenchyma, outer xylem diameter, outer

xylem diameter: outer midrib diameter ratio,

number of vessels, and inner diameter of ves-

sels). Additionally, a robust positive correlation

was evident among xylem parameters (outer

xylem diameter, outer xylem diameter: outer

midrib diameter ratio, number of vessels, and

inner diameter of vessels).

DISCUSSION

Water deficit in banana passionfruit plants

(Passiflora tripartita var. mollissima) results in

a negative effect on growth, leaf number, leaf

area, biomass and leaf area index. These same

positive relationships between growth variables

and stomatal conductance were evident in the

correlation matrix. This decrease is attributed

to the reduction of cell expansion and elonga-

tion because of a loss of turgor in the leaves,

along with a low water potential and decrease in

stomatal conductance (Jaleel et al., 2009), which

are tolerance mechanisms to restrict water loss,

decrease the area exposed to radiation, and,

in turn, decrease the transpiration surface. In

other species such as Passiflora edulis Sims f.

edulis (Lozano-Montaña et al., 2021), P. alata,

P. edulis, P. gibertii, P. setacea, and P. ccincinnata

(Souza et al., 2018), similar results with changes

in growth rate, gas exchange and foliar mor-

phological characteristics under water deficit

conditions have been reported.

The leaf area index (LAI) is a good indica-

tor of plant growth since it is directly related

to the capture of solar radiation and the pro-

duction of dry biomass (Dalirie et al., 2010).

As seen here, a water deficit decreases LAI

and the accumulation of dry biomass (Table

1) since, when the leaf area is reduced, the

Table 2

Anatomical variables measured in Passiflora tripartita var. mollissima plants under two irrigation treatments: control and

water deficit.

Anatomical Characteristics Control Water Deficit Test P-value

Mesophyll (μm) 143.20 ± 7.04 122.6 ± 6.36 t-test < 0.01 *

Upper Epidermis (μm) 19.90 ± 3.27 17.6 ± 2,97 t-test 0.01 *

Lower Epidermis (μm) 8.71 ± 8.71 8.9 ± 8.90 t-test 0.66

Palisade Parenchyma (μm) 65.42 ± 5.52 52.5 ± 3.83 t-test < 0.01 *

Spongy Parenchyma (μm) 48.36 ± 6.40 43.7 ± 4,34 t-test < 0.01 *

Average Outer Midrib Diameter (μm) 475.7 ± 38.4 399.3 ± 9.1 Mann-Withney < 0.01 *

Outer Xylem Diameter (μm) 93.8 ± 7.28 54.2 ± 3.37 t-test < 0.01 *

Xylem Outer Diameter: Midrib outer diameter Ratio 20.0 ± 0.769 13.6 ± 0.772 t-test < 0.01 *

Number of vessels 44 ± 3 31 ± 1 Mann-Withney < 0.01 *

Inner Diameter of vessels (μm) 17.3 ± 1.3 11.8 ± 0.7 t-test < 0.01 *

Stomatal Density (mm-2 stomata) 674.0 ± 229.2 1003.0 ± 26.9 t-test < 0.01 *

* Asterisks indicate significant differences between treatments (P ≤ 0.05).

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photosynthetic efficiency is decreased, which

causes a lower translocation of assimilates to

the sink (Anjum et al., 2017). The increase in

the R/S ratio in the plants with water deficit

resulted from an increase in the root develop-

ment, which is related to the translocation of

photoassimilates to this organ as an avoidance

strategy for water deficit to increase the intake

of water by the plant (Jaleel et al., 2009). The

correlation matrix indicated that as the R/S

ratio increased, the growth variables and size

of certain vascular tissues decreased (negative

correlation). Similar results reported by Loza-

no-Montaña et al. (2021) for Passiflora edulis

Sims f. edulis.

The results showed a decrease in the RWC

of the plants subjected to the water deficit, a

possible response to an osmotic adjustment

to maintain a low turgor in the cells. Similar

results were seen in Passiflora edulis Sims f.

edulis (Lozano-Montaña et al., 2021), and in

various crops of agricultural interest (Anjum

et al., 2017). The gs values at day 42 (150 mmol

H2O m-2 s-1) indicated that there was stomatal

closure resulting from the effect of the water

deficit, which meant a decrease in gas exchange

(Liu et al., 2022). Stomatal closure is mediated

by abscisic acid (ABA), and, with a water defi-

cit, this growth regulator is produced quickly,

which causes an increase in cytosolic calcium

in the guard cells, causing the release of anions

that leads to the depolarization of the mem-

brane, so cells lose turgor, producing stomatal

closure in the leaves (Liu et al., 2022).

No significant changes were observed in

the variable Fv/Fm during the experiment. The

values ranged between 0.81 and 0.83, which

is typical in plants that do not present stress

or damage at the level of the PSII, suggesting

that banana passionfruit plants could have

some protection mechanisms for photosystem

II from water deficit (Maxwell & Johnson 2000;

Fig. 4. Correlation matrix for physiological and anatomical parameters measure in banana passionfruit plants 49 after

irrigation treatments began. NoL: number of leaves; gs: stomatal conductance; Fv/Fm: maximum quantum yield of PSII II;

Chl: total chlorophyll content; RWC: relative water content; R/S: root: shoot ratio; SDW: shoot dry weight; RDW: root dry

weight; Meso: mesophyll; UE: upper epidermis; LE: lower epidermis; PP: palisade parenchyma; SP: spongy parenchyma; SD:

stomatal density; MD: outer midrib diameter; XD: outer xylem diameter; X:M: outer xylem diameter: outer midrib diameter

ratio; NoV: number of vessels; IDV: inner diameter of vessels.

10 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

Murchie & Lawson 2013). The stability in the

Fv/Fm values, from the day on which the water

deficit treatment started until day 35, is con-

sistent with the report by Gomes et al. (2012)

for Passiflora edulis Sims, which suggests that

the maximum photochemical efficiency of PSII

will only decrease in banana passionfruit plants

in the face of possible severe stress. Addition-

ally, when evaluating the total chlorophyll con-

tent, no significant differences were observed

between the treatments although there was a

tendency to decrease from 21 dat, which sug-

gests a possible relationship with the lower per-

formance of the maximum potential quantum

efficiency of photosystem II in the subsequent

days (Fig. 2C, Fig. 2A, respectively). Similar

results have been reported in P. edulis f. edulis

(Lozano-Montaña et al., 2021). A slight reduc-

tion in total chlorophylls (Fig. 2C) could suggest

that there was a low capacity for light harvest-

ing and probably degradation or unmasking of

the accessory pigments of the light harvesting

antenna (Mafakheri et al., 2010).

Among the physiological variables, the

most sensitive to water deficit was the gs,

which controls stomatal opening, an immedi-

ate response to irrigation reductions. Similar

results were reported by Lozano-Montaña et

al. (2021) for P. edulis Sims f. edulis, by (Souza

et al., 2018) for P. alata, P. edulis, P. gibertii, P.

setacea, and P. cincinnata, and by Gomes et al.

(2018) for P. edulis Sims f. flavicarpa. Banana

passionfruit plants, when faced with a water

deficit, close stomata to minimize water loss

and, therefore, decrease the accumulation of

aerial biomass.

The anatomical analysis showed a decrease

in the leaf tissues in the banana passionfruit

plants subjected to water deficit, resulting in

a denser arrangement of cells (Fig. 3B, Fig

3D). The reduction in the thickness of the

tissue (Table 2) implied a decrease in the dif-

fusion of CO2 inside the leaves, a reduction of

stomatal conductance, and a reduced rate of

water transpiration to ensure an efficient use of

water by the plants (Chartzoulakis et al., 2002).

These changes in the leaf lamina tissue thick-

ness can also affect CO2 conductance in the

mesophyll (Cousins et al. 2020). Similar results

were reported by Souza et al. (2018) for Passi-

flora spp. and by Chartzoulakis et al. (2002) for

two avocado cultivars under water deficit stress.

In addition, increased stomatal density

was observed in the banana passionfruit plants

subjected to water deficit, which is a strategy to

improve stomatal opening in less time, result-

ing in balanced gas exchange, better response

under water scarcity conditions (Souza et

al., 2018), and better transpiration control to

minimize water loss (Ennajeh et al., 2010).

Similar results for stomatal density changes

resulting from water deficit have been reported

in other species, such as olive trees (Enna-

jeh et al., 2010) and Astragalus gombiformis

(Boughalleb et al., 2014).

Another strategy in the banana passion-

fruit plants for the water deficit was a decrease

in the diameter of the xylem vessels (Table 2).

This mechanism is positively correlated with

the volume of water transported in plants and is

inversely related to the vascular system (Inoue

et al., 2019). Narrower vessels probably increase

resistance to water flow, decrease the prob-

ability of cavitation in xylem vessels, and keep

water columns under greater tension because

they have a greater surface area in relation to

the volume and a greater proportion of water

molecules adhered to the wall (Boughalleb et

al., 2014; Vasellati et al., 2001).

Our data showed that Passiflora tripartita

var. mollissima plants had different tolerance

mechanisms for the water deficit when com-

pared to the control plants. They decrease the

shoot dry biomass and invest in root growth,

with high R/S values. These plants also carried

out water adjustments with stomatal closure, as

evidenced in the low stomatal conductance val-

ues, decreased RWC, and thinner tissues, along

with a decreased xylem vessel diameter, prob-

ably to avoid cavitation, tolerate water deficits

and perform better.

Ethical statement: the authors declare

that they all agree with this publication and

made significant contributions; that there is

no conflict of interest of any kind; and that we

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e56532, enero-diciembre 2024 (Publicado Jul. 11, 2024)

followed all pertinent ethical and legal proce-

dures and requirements. All financial sources

are fully and clearly stated in the acknowledg-

ments section. A signed document has been

filed in the journal archives.

ACKNOWLEDGMENTS

This work was supported by the Red

Nacional para la Bioprospección de Frutas

Tropicales-RIFRUTBIO Código Hermes 20174,

and Ministerio de Ciencia, Tecnología e Inno-

vación, Contract No. 459-2013, Universidad

Nacional de Colombia, Universidad de Cun-

dinamarca, Universidad de Cartagena, Univer-

sidad de Nariño, Frutipaz. Thanks to optical

equipment laboratory of Departamento de

Biología, Universidad Nacional de Colombia,

Bogotá and to Jessica Vaca for participate in

sampling events.

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