Photosynthetic Electron Transport in Single Guard Cells as Measured by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is a powerful new tool for studying chemical and biological processes. It records changes in faradaic current as a microelectrode ([less than equal]7 [mu]m in diameter) is moved across the surface of a sample. The current varies as a function of both distance from the surface and the surface's chemical and electrical properties. We used SECM to examine in vivo topography and photosynthetic electron transport of individual guard cells in Tradescantia fluminensis, to our knowledge the first such analysis for an intact plant. We measured surface topography at the micrometer level and concentration profiles of O2 evolved in photosynthetic electron transport. Comparison of topography and oxygen profiles above single stomatal complexes clearly showed photosynthetic electron transport in guard cells, as indicated by induction of O2 evolution by photosynthetically active radiation. SECM is unique in its ability to measure topography and chemical fluxes, combining some of the attributes of patch clamping with scanning tunneling microscopy. In this paper we suggest several questions in plant physiology that it might address.     

Action of growth regulators on the cotyledonary stomata ofCucumis sativus L.: Structure and ontogeny

Anomocytic stomata and stomata with single subsidiary cells are commonly observed Sometimes a stoma appears anisocytic. Double cytoplasmic connections between nearby stomata and division of guard cells with persistent or degenerating nuclei are seen in GA. One or more divisions of guard cells, displaced guard cells and single guard cells with or without pore are noticed in SUC. Formation of single guard cells is a common feature in TIBA. Paracytic stomata, one and a half stomata and persistent stomatal initials are seen in SUL. COUM seems to be not inhibitory inCucumis sativus. In COL stomata with unequal guard cells, unequal stomatal cells with thickening in between but without intervening pore, stoma with double pores, persistent stomatal initials which may be solitary or in groups with varying shapes and with one or two nuclei of different shapes are noticed. The growth regulators affect the frequency of stomata, epidermal cells; stomatal index; size of guard and epidermal cells.     

The stomata of the fern Adiantum capillus-veneris do not respond to CO2 in the dark and open by photosynthesis in guard cells

The stomata of the fern Adiantum capillus-veneris lack a blue light-specific opening response but open in response to red light. We investigated this light response of Adiantum stomata and found that the light wavelength dependence of stomatal opening matched that of photosynthesis. The simultaneous application of red (2 micromol m(-2) s(-1)) and far-red (50 micromol m(-2) s(-1)) light synergistically induced stomatal opening, but application of only one of these wavelengths was ineffective. Adiantum stomata did not respond to CO2 in the dark; the stomata neither opened under a low intercellular CO2 concentration nor closed under high intercellular CO2 concentration. Stomata in Arabidopsis (Arabidopsis thaliana), which were used as a control, showed clear sensitivity to CO2. In Adiantum, stomatal conductance showed much higher light sensitivity when the light was applied to the lower leaf surface, where stomata exist, than when it was applied to the upper surface. This suggests that guard cells likely sensed the light required for stomatal opening. In the epidermal fragments, red light induced both stomatal opening and K+ accumulation in guard cells, and both of these responses were inhibited by a photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The stomatal opening was completely inhibited by CsCl, a K+ channel blocker. In intact fern leaves, red light-induced stomatal opening was also suppressed by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. These results indicate that Adiantum stomata lack sensitivity to CO2 in the dark and that stomatal opening is driven by photosynthetic electron transport in guard cell chloroplasts, probably via K+ uptake.     

The effect of exogenous abscisic acid on stomatal development, stomatal mechanics, and leaf gas exchange in Tradescantia virginiana

Gas exchange parameters and stomatal physical properties were measured in Tradescantia virginiana plants grown under well-watered conditions and treated daily with either distilled water (control) or 3.0 mM abscisic acid (ABA). Photosynthetic capacity (CO(2) assimilation rate for any given leaf intercellular CO(2) concentration [c(i)]) and relative stomatal sensitivity to leaf-to-air vapor-pressure difference were unaffected by the ABA treatment. However, at an ambient CO(2) concentration (c(a)) of 350 micromol mol(-1), ABA-treated plants operated with significantly lower c(i). ABA-treated plants had significantly smaller stomata and higher stomatal density in their lower epidermis. Stomatal aperture versus guard cell pressure (P(g)) characteristics measured with a cell pressure probe showed that although the form of the relationship was similar in control and ABA-treated plants, stomata of ABA-treated plants exhibited more complete closure at P(g) = 0 MPa and less than half the aperture of stomata in control plants at any given P(g). Scaling from stomatal aperture versus P(g) to stomatal conductance versus P(g) showed that plants grown under ABA treatment would have had significantly lower maximum stomatal conductance and would have operated with lower stomatal conductance for any given guard cell turgor. This is consistent with the observation of lower c(i)/c(a) in ABA-treated plants with a c(a) of 350 micromol mol(-1). It is proposed that the ABA-induced changes in stomatal mechanics and stomatal conductance versus P(g) characteristics constitute an improvement in water-use efficiency that may be invoked under prolonged drought conditions.     

Morphogenetic effects of various growth substances on the cotyledonary stomata of brinjal and tomato

The effect of different growth substances on the development of normal and abnormal stomata are presented. Anomocytic, paracytic, anisocytic and stoma with a single subsidiary cell are observed. Abnormal developments like persistent stomatal cells, degeneration of guard cells, unusual thickening, unequal guard cells, single guard cells and size and shape of the pore are noticed in various growth substances. The growth substances also affect the stomatal frequency, stomatal index, epidermal frequency and size of guard and epidermal cells in both the plants. The highest meristematic activity is found in MOR 100 ppm in brinjal and in GA 25 ppm in tomato. The largest size of stomata is found in COL 25 ppm in brinjal and in MH 50 ppm in tomato. The same growth substance responds differently in the two plants.     

Abnormal Stomatal Behaviour and Hormonal Imbalance in flacca, a Wilty Mutant of Tomato: EFFECT OF ABSCISIC ACID AND AUXIN ON STOMATAL BEHAVIOUR AND PEROXIDASE ACTIVITY

The wilty tomato mutant flacca and the normal variety RheinlandsRuhm were compared in terms of: (1) potassium transport intoand out of the guard cells, (2) cell wall properties which includeprotein, hydroxyproline and peroxidase activity, and (3) activityof indol-3yl-acetic acid oxidase. Also studied were the effectsof auxin on stomatal behaviour and peroxidase activity whenapplied to normal plants during development, and the short-termeffect of abscisic acid on the resistance of flacca stomatato closure under plasmolysis. Potassium transport, wall protein and hydroxyproline all seemedto be equal in mutant and normal plants. Peroxidase activitywas higher in the soluble and wall fractions of the mutant,and decreased toward normal in the mutant treated with abscisicacid. More stomata were open and peroxidase activity was higherin normal plants treated with auxin during development. Thepercentage of open stomata under plasmolysis was lower and theiraperture size was smaller in the epidermal strips taken fromabscisic-acid-treated mutant plants than from control mutantplants.     

Fern and lycophyte guard cells do not respond to endogenous abscisic acid

Stomatal guard cells regulate plant photosynthesis and transpiration. Central to the control of seed plant stomatal movement is the phytohormone abscisic acid (ABA); however, differences in the sensitivity of guard cells to this ubiquitous chemical have been reported across land plant lineages. Using a phylogenetic approach to investigate guard cell control, we examined the diversity of stomatal responses to endogenous ABA and leaf water potential during water stress. We show that although all species respond similarly to leaf water deficit in terms of enhanced levels of ABA and closed stomata, the function of fern and lycophyte stomata diverged strongly from seed plant species upon rehydration. When instantaneously rehydrated from a water-stressed state, fern and lycophyte stomata rapidly reopened to predrought levels despite the high levels of endogenous ABA in the leaf. In seed plants under the same conditions, high levels of ABA in the leaf prevented rapid reopening of stomata. We conclude that endogenous ABA synthesized by ferns and lycophytes plays little role in the regulation of transpiration, with stomata passively responsive to leaf water potential. These results support a gradualistic model of stomatal control evolution, offering opportunities for molecular and guard cell biochemical studies to gain further insights into stomatal control.     

Slow photosynthetic induction and low photosynthesis in Paphiopedilum armeniacum are related to its lack of guard cell chloroplast and peculiar stomatal anatomy

Paphiopedilum and Cypripedium are close relatives in the subfamily Cypripedioideae. Cypripedium leaves contain guard cell chloroplasts, whereas Paphiopedilum do not. It is unclear whether the lack of guard cell chloroplasts affects photosynthetic induction, which is important for understory plants to utilize sunflecks. To understand the role of guard cell chloroplasts in photosynthetic induction of Paphiopedilum and Cypripedium, the stomatal anatomy and photosynthetic induction of Paphiopedilum armeniacum and Cypripedium flavum were investigated at different ratios of red to blue light. The highest stomatal opening and photosynthesis of intact leaves in P. armeniacum were induced by irradiance enriched with blue light. Its stomatal opening could be induced by red light 250 µmol m^?2 s^?1, but the magnitude of stomatal opening was lower than those at the other light qualities. However, the stomatal opening and photosynthesis of C. flavum were highly induced by mixed blue and red light rather than pure blue or red light. The two orchid species did not differ in stomatal density, but P. armeniacum had smaller stomatal size than C. flavum. The stomata of P. armeniacum were slightly sunken into the leaf epidermis, while C. flavum protruded above the leaf surface. The slower photosynthetic induction and lower photosynthetic rate of P. armeniacum than C. flavum were linked to the lack of guard cell chloroplasts and specific stomatal structure, which reflected an adaptation of Paphiopedilum to periodic water deficiency in limestone habitats. These results provide evidence for the morphological and physiological evolution of stomata relation for water conservation under natural selection.     

安徽黄精属(Polygonatum)植物叶表皮研究

利用光学显微镜及扫描电子显微镜观察了安徽省黄精属９种植物的叶表皮;统计并测量了气孔类型、气孔大小、气孔密度及气孔指数等;描述了表皮角质膜、蜡质纹饰、气孔的形状及气孔外拱盖等有关特征。结果表明：黄精属植物叶表皮气孔器类型属只有２个保卫细胞而无任何副卫细胞的单子叶植物气孔器类型。气孔的某些特征,如气孔器类型、气孔器分布特征、表皮细胞形状及垂周壁式样、角质层及蜡质纹饰等在种间差异不大,可作种间区别的次级特征用。     

Stomatal opening by fusicoccin is accompanied by depolymerization of actin filaments in guard cells

Actin in guard cells is assembled in a radial pattern when stomata are induced to open under light, but the filaments are disassembled when stomata are closed under darkness or by abscisic acid (S.-O. Eun and Y. Lee, 1997, Plant Physiol. 115: 1491–1498). To test if signals that open stomata commonly generate the polymerized form of actin in guard cells, leaves of Commelina communis L. were treated with a potent stomatal opening agent, fusicoccin, and the actin organization examined by immunolocalization techniques. When stomata were induced to open by fusicoccin, hardly any of the filamentous form of actin was detected; instead, the actin resembled that present in guard cells that had been treated with an antagonist to actin filaments, cytochalasin D, and showed a sharp contrast to the long filaments developed in illuminated guard cells. Furthermore, treatment of illuminated leaves with fusicoccin disintegrated actin filaments that had already been formed in the guard cells. Preincubation of leaves with phalloidin, which interferes with fusicoccin-induced actin depolymerization, delayed fusicoccin-induced opening during the early phase. These observations suggest that the prevention of actin filament formation and/or depolymerization of actin filaments may accelerate the stomatal opening process in response to fusicoccin. Received: 1 October 1999 / Accepted: 29 November 1999     

Stomatal oscillations at small apertures: indications for a fundamental insufficiency of stomatal feedback-control inherent in the stomatal turgor mechanism.

Continuous measurements of stomatal aperture simultaneously with gas exchange during periods of stomatal oscillations are reported for the first time. Measurements were performed in the field on attached leaves of undisturbed Sambucus nigra L. plants which were subjected to step-wise increases of PPFD. Oscillations only occurred when stomatal apertures were small under high water vapour mole fraction difference between leaf and atmosphere (DeltaW). They consisted of periodically repeated opening movements transiently leading to very small apertures. Measurements of the area of the stomatal complex in parallel to the determination of aperture were used to record volume changes of guard cells even if stomata were closed. Stomatal opening upon a light stimulus required an antecedent guard cell swelling before a slit occurred. After opening of the slit the guard cells again began to shrink which, with some delay, led to complete closure. Opening and closing were rhythmically repeated. The time-lag until initial opening was different for each individual stoma. This led to counteracting movements of closely adjacent stomata. The tendency to oscillate at small apertures is interpreted as being a failure of smoothly damped feedback regulation at the point of stomatal opening: Volume changes are ineffective for transpiration if stomata are still closed; however, at the point of initial opening transpiration rate rises steeply. This discontinuity together with the rather long time constants inherent in the stomatal turgor mechanism makes oscillatory overshooting responses likely if at high DeltaW the 'nominal value' of gas exchange demands a small aperture.     

Stomatal development and patterning in Arabidopsis leaves

The functional unit for gas exchange between plants and the atmosphere is the stomatal complex, an epidermal structure composed of two guard cells, which delimit a stomatal pore, and their subsidiary cells. In the present work, we define the basic structural unit formed in Arabidopsis thaliana during leaf development, the anisocytic stomatal complex. We perform a cell lineage analysis by transposon excision founding that at least a small percentage of stomatal complexes are unequivocally non-clonal. We also describe the three-dimensional pattern of stomata in the Arabidopsis leaf. In the epidermal plane, subsidiary cells of most stomatal complexes contact the subsidiary cells of immediately adjacent complexes. This minimal distance between stomatal complexes allows each stoma to be circled by a full complement of subsidiary cells, with which guard cells can exchange water and ions in order to open or to close the pore. In the radial plane, stomata (and their precursors, the meristemoids) are located at the junctions of several mesophyll cells. This meristemoid patterning may be a consequence of signals that operate along the radial axis of the leaf, which establish meristemoid differentiation precisely at these places. Since stomatal development is basipetal, these radially propagated signals may be transmitted in the axial direction, thus guiding stomatal development through the basal end of the leaf.     

Array and distribution of actin filaments in guard cells contribute to the determination of stomatal aperture

Actin filaments in guard cells and their dynamics function in regulating stomatal movement. In this study, the array and distribution of actin filaments in guard cells during stomatal movement were studied with two vital labeling, microinjection of alexa-phalloidin in Vicia faba and expression of GFP-mTn in tobacco. We found that the random array of actin filaments in the most of the closed stomata changed to a ring-like array after stomatal open. And actin filaments, which were throughout the cytoplasm of guard cells of closed stomata (even distribution), were mainly found in the cortical cytoplasm in the case of open stomata (cortical distribution). These results revealed that the random array and even distribution of actin filaments in guard cells may be required for keeping the closed stomata; similarly, the ring-like array and cortical distribution of actin filaments function in sustaining open stomata. Furthermore, we found that actin depolymerization, the trait of moving stomata, facilitates the transformation of actin array and distribution with stomatal movement. So, the depolymerization of actin filaments was favorable for the changes of actin array and distribution in guard cells and thus facilitated stomatal movement.     

Variation in the structure and development of foliar stomata in the Euphorbiaceae

The structure and ontogeny of foliar stomata were studied in 50 species of 28 genera belonging to 17 tribes of the family Euphorbiaceae. The epidermal cells are either polygonal, trapezoidal, or variously elongated in different directions and diffusely arranged. The epidermal anticlinal walls are either straight, arched or sinuous. The architecture of cuticular striations varies with species. The mature stomata are paracytic (most common), anisocytic, anomocytic and diacytic. Occasionally a stoma may be tetracytic, cyclocytic or with a single subsidiary cell. The ontogeny of paracytic stomata is mesogenous dolabrate or trilabrate, mesoperigenous dolabrate; that of diacytic stomata is mesogenous dolabrate, whereas that of anisocytic stomata is mesogenous trilabrate; rarely an anisocytic stoma may be mesoperigenous. Hemiparacytic stomata are mesoperigenous unilabrate; tetracytic stomata are mesoperigenous dolabrate and anomocytic stomata perigenous. Abnormalities encountered include four types of contiguous stomata, stomata with a single or both guard cells aborted and persistent stomatal initials. Cytoplasmic connections between the guard cells of two adjacent stomata or the guard cell of a stoma and an adjacent epidermal/subsidiary cell, or both types occurring in a species, were noticed. The stomatal development, distribution, diversity and basic stomatal type with reference to systematics are discussed.     

Elevated carbon dioxide affects the patterning of subsidiary cells in Tradescantia stomatal complexes

The influence of elevated CO₂ concentration (670 ppm) on thestructure, distribution, and patterning of stomata in Tradescantialeaves was studied by making comparisons with plants grown atambient CO₂. Extra subsidiary cells, beyond the normal complementof four per stoma, were associated with nearly half the stomatalcomplexes on leaves grown in elevated CO₂. The extra cells sharedcharacteristics, such as pigmentation and expansion, with thetypical subsidiary cells. The position and shape of the extrasubsidiary cells in face view differed in the green and purplevarieties of Tradescantia. Substomatal cavities of complexeswith extra subsidiary cells appeared larger than those foundin control leaves. Stomatal frequency expressed on the basisof leaf area did not differ from the control. Stomatal frequencybased on cell counts (stomatal index) was greater in leavesgrown in CO₂-enriched air when all subsidiary cells were countedas part of the stomatal complex. This difference was eliminatedwhen subsidiary cells were included in the count of epidermalcells, thereby evaluating the frequency of guard cell pairs.The extra subsidiary cells were, therefore, recruited from theepidermal cell population during development. Stomatal frequencyin plants grown at elevated temperature (29 C) was not significantlydifferent from that of the control (24 C). The linear aggregationsof stomata were similar in plants grown in ambient and elevatedCO₂. Since enriched CO₂ had no effect on the structure or patterningof guard cells, but resulted in the formation of additionalsubsidiary cells, it is likely that separate and independentevents pattern the two cell types. Plants grown at enrichedCO₂ levels had significantly greater internode lengths, butleaf area and the time interval between the appearance of successiveleaves were similar to that of control plants. Porometric measurementsrevealed that stomatal conductance of plants grown under elevatedCO₂ was lower than that of control leaves and those grown atelevated temperature. Tradescantia was capable of regulatingstomatal conductance in response to elevated CO₂ without changingthe relative number of stomata present on the leaf. Key words: Elevated CO₂, stomata, subsidiary cells, patterning     

Reductions in mesophyll and guard cell photosynthesis impact on the control of stomatal responses to light and CO2

Transgenic antisense tobacco plants with a range of reductions in sedoheptulose-1,7-bisphosphatase (SBPase) activity were used to investigate the role of photosynthesis in stomatal opening responses. High resolution chlorophyll a fluorescence imaging showed that the quantum efficiency of photosystem II electron transport (F(q)(')/F(m)(')) was decreased similarly in both guard and mesophyll cells of the SBPase antisense plants compared to the wild-type plants. This demonstrated for the first time that photosynthetic operating efficiency in the guard cells responds to changes in the regeneration capacity of the Calvin cycle. The rate of stomatal opening in response to a 30 min, 10-fold step increase in red photon flux density in the leaves from the SBPase antisense plants was significantly greater than wild-type plants. Final stomatal conductance under red and mixed blue/red irradiance was greater in the antisense plants than in the wild-type control plants despite lower CO(2) assimilation rates and higher internal CO(2) concentrations. Increasing CO(2) concentration resulted in a similar stomatal closing response in wild-type and antisense plants when measured in red light. However, in the antisense plants with small reductions in SBPase activity greater stomatal conductances were observed at all C(i) levels. Together, these data suggest that the primary light-induced opening or CO(2)-dependent closing response of stomata is not dependent upon guard or mesophyll cell photosynthetic capacity, but that photosynthetic electron transport, or its end-products, regulate the control of stomatal responses to light and CO(2).     

Form,development and function of grass stomata

Stomata are cellular breathing pores on leaves that open and close to absorb photosynthetic carbon dioxide and to restrict water loss through transpiration, respectively. Grasses (Poaceae) form morphologically innovative stomata, which consist of two dumbbell‐shaped guard cells flanked by two lateral subsidiary cells (SCs). This ‘graminoid’ morphology is associated with faster stomatal movements leading to more water‐efficient gas exchange in changing environments. Here, we offer a genetic and mechanistic perspective on the unique graminoid form of grass stomata and the developmental innovations during stomatal cell lineage initiation, recruitment of SCs and stomatal morphogenesis. Furthermore, the functional consequences of the four‐celled, graminoid stomatal morphology are summarized. We compile the identified players relevant for stomatal opening and closing in grasses, and discuss possible mechanisms leading to cell‐type‐specific regulation of osmotic potential and turgor. In conclusion, we propose that the investigation of functionally superior grass stomata might reveal routes to improve water‐stress resilience of agriculturally relevant plants in a changing climate.     

Role of malate synthesis mediated by phosphoenolpyruvate carboxylase in guard cells in the regulation of stomatal movement

To clarify the pathway and role of malate synthesis in guard cells, epidermal strips isolated from Vicia faba L. leaflets were treated with 3,3-dichloro-2-dihydroxyphosphinoylmethyl-2-propenoate (DCDP), a specific inhibitor of phosphoenolpyruvate carboxylase (PEPC). When dark-closed stomata were illuminated, malate accumulated in guard cells and stomata opened; these were inhibited by 60% and 30%, respectively, by 5 mM DCDP treatment. When light-opened stomata were treated with DCDP, both malate level in guard cells and stomatal aperture decreased. Treatment with 5 mM DCDP partially inhibited CO2 incorporation into malate in guard cells. Treatment with mannitol at 0.4 M (osmotic stress) in the light increased malate level in guard cells and closed stomata. DCDP treatment decreased both malate level and stomatal aperture under stressed condition. These results show that malate synthesis in the light under both non-stressed and stressed conditions is dependent on PEPC activity. The extent of the decrease in malate level by DCDP treatment was larger under stressed condition than under nonstressed condition, suggesting that osmotic stress may enhance the activity of this pathway of malate synthesis which is induced by light. Role of malate synthesis in guard cells is discussed.     

Abaxial and adaxial stomata from Pima cotton (Gossypium barbadense L.) differ in their pigment content and sensitivity to light quality

Sensitivity to light quality and pigment composition were analysed and compared in abaxial and adaxial stomata of Gossypium barbadense L. (Pima cotton). In most plants, abaxial (lower) stomatal conductances are higher than adaxial (upper) ones, and stomatal opening is more sensitive to blue light than to red. In greenhouse-grown Pima cotton, abaxial stomatal conductances were two to three times higher than adaxial ones. In contrast, adaxial stomatal conductances were 1·5 to two times higher than abaxial ones in leaves from growth chamber-grown plants. To establish whether light quality was a factor in the regulation of the relationship between abaxial and adaxial stomatal conductances, growth-chamber-grown plants were exposed to solar radiation outdoors and to increased red light in the growth chamber. In both cases, the ratios of adaxial to abaxial stomatal conductance reverted to those typical of greenhouse plants. We investigated the hypothesis that adaxial stomata are more sensitive to blue light and abaxial stomata are more sensitive to red light. Measurements of stomatal apertures in mechanically isolated epidermal peels from growth chamber and greenhouse plants showed that adaxial stomata opened more under blue light than under red light, while abaxial stomata had the opposite response. Using HPLC, we quantified the chlorophylls and carotenoids extracted from isolated adaxial and abaxial guard cells. All pigments analysed were more abundant in the adaxial than in the abaxial guard cells. Antheraxanthin and β-carotene contents were 2·3 times higher in adaxial than in abaxial guard cells, comparing with ad/ab ratios of 1·5–1·9 for the other pigments. We conclude that adaxial and abaxial stomata from Pima cotton have a differential sensitivity to light quality and their distinct responses are correlated with different pigment content.     

Effect of Cadmium Stress on the Growth,Physiology, Stress Markers,Antioxidants and Stomatal Behaviour of Two Genotypes of Chickpea ( <i>Cicer arietinum </i>L.)

The current work was performed to know the impact of cadmium (Cd) toxicity on two different genotypes of chickpea (Cicer arietinum L.) namely Pusa-BG1053 and Pusa-BG372. Cadmium was applied in the form of cadmium chloride (CdCl₂), in varying levels, 0, 25, 50, 75, and 100 mg Cd kg^-1 soil. Plant growth as well as physiological attributes were decreased with increasing concentration of Cd. Both genotypes showed the maximum and significant reduction at the maximum dose of Cd (100 mg Cd kg^-1 soil). Results of this study proved that the genotype Pusa-BG1053 was more tolerant and showed a lower decline in growth, photosynthetic and biochemical attributes than Pusa-BG372. This later genotype showed the maximum reduction and was sensitive to Cd stress. A better activity of antioxidants protected Pusa-BG1053 from Cd toxicity; on the other hand, the activity of antioxidants was much lower in Pusa-BG372. Scanning electron microscopic studies showed differences in both genotypes. In Pusa-BG1053, stomatal quantity was higher and stomata were slightly close to the characteristic guard cells. In Pusa-BG372 stomata were lower, slightly open and with highly affected guard cells. Root cell mortality due to the harsh effects of Cd appeared to be more evident in Pusa-BG372 than Pusa-BG1053, which was visible under a confocal microscope. As a result of this study, Pusa-BG1053 was a more tolerant genotype, and exhibited a minimum reduction in terms of all studied parameters than Pusa-BG372, which was a sensitive genotype to Cd toxicity.