Physiological determinants of performance in gerbera varieties under polyhouse conditions of Telangana

Introduction

Gerbera (Gerbera jamesonii Bolus ex Hooker f.) has emerged as a commercially important cut flower worldwide, with increasing demand for year-round production under protected cultivation systems (Kaur et al., 2021) [4] . While substantial research has focused on agronomic performance and genetic improvement of gerbera, relatively limited attention has been given to understanding the physiological basis of varietal differences in productivity and quality under controlled environments (Gupta & Bashir, 2024) [3] . Physiological traits, particularly those related to photosynthetic efficiency and resource utilization, fundamentally determine crop performance and adaptation to specific growing conditions (Vijayalaxmi et al., 2021) [12] . Leaf area and chlorophyll content are two critical physiological parameters influencing photosynthetic capacity and, consequently, biomass production and flower yield in floricultural crops (Prajapati et al., 2017) [6] . Leaf area determines light interception capacity and photosynthetic surface, while chlorophyll content reflects the photosynthetic apparatus' potential for light absorption and energy conversion (Chobe et al., 2010) [2] . In gerbera, which produces multiple flower cycles throughout the year under protected conditions, sustained photosynthetic activity is essential for continuous flower production and quality maintenance (Sil et al., 2017) [7] . Previous studies have reported significant variation in physiological traits among gerbera varieties under different growing conditions. Chobe et al. (2010) [2] observed 45-60% variation in leaf area among thirty gerbera cultivars, while Vijayalaxmi et al. (2021) [12] reported substantial differences in chlorophyll content among ten varieties under polyhouse conditions. However, comprehensive understanding of how these physiological traits influence specific growth, yield, and quality parameters in gerbera remains limited, particularly under subtropical polyhouse conditions. Protected cultivation in polyhouses presents unique physiological challenges and opportunities for crop production. The modified microclimate, characterized by controlled temperature, humidity, and light conditions, can significantly influence plant physiological processes (Ahlawat et al., 2012) [1] in leaf area among thirty gerbera cultivars, while Vijayalaxmi et al. (2021) [12] reported substantia1l. Understanding varietal responses to these conditions at the physiological level is crucial for optimizing cultivation practices and selecting appropriate varieties for specific production systems. In Telangana state, India, protected floriculture has expanded significantly, with gerbera becoming an economically important crop (Telangana State Horticulture Department, 2022) [11] . However, systematic investigation of physiological determinants of gerbera performance under local polyhouse conditions is lacking. Such information would be valuable for developing physiological selection criteria in breeding programs and for optimizing cultivation practices based on varietal physiological characteristics. This study aimed to investigate physiological determinants of performance among ten gerbera varieties under naturally ventilated polyhouse conditions. Specific objectives were to: (1) quantify variation in key physiological parameters (leaf area and chlorophyll content) among varieties, (2) analyze relationships between physiological traits and growth, yield, and quality parameters, (3) identify physiological factors contributing to superior performance, and (4) classify varieties based on physiological characteristics.

Materials and Methods

Experimental Site and Design

The study was conducted from December 2024 to May 2025 at the Floricultural Research Station, Rajendranagar, Hyderabad, Telangana, India (17.32°N, 78.40°E, altitude 542 m). The experiment employed a Randomized Block Design with ten treatments (varieties) and three replications. The varieties evaluated were: T1 (Gonzo), T2 (Fozzie), T3 (Janice), T4 (Camilla), T5 (Floyd), T6 (Bunny), T7 (Beaker), T8 (Black Pearl), T9 (Honeydew), and T10 (Tracy). All varieties were Pomponi Mini type, obtained as tissue-cultured plantlets from KF Bioplant, Pune, Maharashtra.

Polyhouse Conditions and Crop Management

The study was conducted in a naturally ventilated polyhouse covered with 200-micron UV-stabilized polyethylene film. Raised beds (45 cm × 80 cm) were prepared with a growing medium of red soil, farmyard manure, and cocopeat (2:1:1 v/v). Plantlets were transplanted on 17 December 2024 at 30 × 40 cm spacing. Standard cultivation practices were followed, including drip irrigation, balanced fertilization (19:19:19 NPK during vegetative phase; 12:16:0 and 13:0:45 during reproductive phase), and integrated pest management.

Data Collection 2.3.1 Physiological Parameters

 Leaf area (cm²): Measured at 150 days after planting using a leaf area meter (Bionics BST/YMJ-A). Five fully expanded leaves from the middle whorl were sampled per plant.  Chlorophyll content (SPAD units): Measured at 150 days after planting using a SPAD meter (Minolta SPAD-502).

Readings were taken from the middle portion of five fully expanded leaves per plant, avoiding major veins.

Growth

Statistical Analysis

Data were analyzed using analysis of variance (ANOVA) for Randomized Block Design as per Panse and Sukhatme (1954) [5] . Treatment means were compared using Critical Difference (CD) at 5% probability level. Correlation coefficients were calculated to examine relationships between physiological and performance parameters. Path analysis was performed to determine direct and indirect effects of physiological traits on flower yield. Principal Component Analysis (PCA) was conducted to identify major sources of variation, and cluster analysis using Ward's method was performed to classify varieties based on physiological characteristics. All statistical analyses were conducted using R software version 4.2.1.

Results and Discussion

Variation in Physiological Parameters

Significant differences (p<0.05) were observed among the ten gerbera varieties for both leaf area and chlorophyll content at 150 days after planting (Table 1). Fozzie (T2) recorded the maximum leaf area (109.06 cm²) and chlorophyll content (47.41 SPAD units), while Honeydew (T9) showed the minimum leaf area (56.78 cm²) and Camilla (T4) recorded the minimum chlorophyll content (22.68 SPAD units). The range of variation was substantial, with leaf area varying by 92% between maximum and minimum values, and chlorophyll content varying by 109%. This extensive genotypic variation provides opportunities for selection and breeding focused on physiological traits. The superior leaf area in Fozzie indicates greater photosynthetic surface area, potentially enabling higher carbon assimilation rates. This finding aligns with Chobe et al. (2010) [2] , who reported significant variation in leaf area among gerbera cultivars and its importance for flower production. The high chlorophyll content in Fozzie suggests efficient light harvesting capacity, which is particularly important under polyhouse conditions where light intensity may be suboptimal compared to open field conditions. Vijayalaxmi et al. (2021) [12] similarly observed substantial variation in chlorophyll content among gerbera varieties under protected cultivation.

Correlation Between Physiological and Performance Parameters

Correlation analysis revealed significant relationships between physiological parameters and various growth, yield, and quality attributes ( The strong correlation between leaf area and flower yield (r=0.82) underscores the importance of photosynthetic surface area in determining reproductive output. This relationship is physiologically logical, as larger leaf area enables greater light interception and carbon fixation, providing more assimilates for flower development. Similarly, the correlation between chlorophyll content and fresh weight (r=0.65) suggests that photosynthetic efficiency influences biomass accumulation and flower substance. These findings support the concept that physiological traits directly influence agronomic performance in gerbera, as previously suggested by Soni and Godara (2017) [8] in their evaluation of gerbera varieties under greenhouse conditions.

Path Analysis of Physiological Determinants

Path analysis was conducted to quantify direct and indirect effects of physiological parameters on flower yield (Figure 1, Table 3). Leaf area exhibited the highest direct effect on flower yield (0.62), followed by chlorophyll content (0.38). The indirect effect of leaf area through chlorophyll content was 0.24, while the indirect effect of chlorophyll content through leaf area was 0.31. The total determination coefficient (R²) for the path model was 0.74, indicating that 74% of variation in flower yield could be explained by these two physiological parameters. The high direct effect of leaf area on flower yield confirms its role as a primary physiological determinant of productivity in gerbera. This finding has practical implications for selection in breeding programs and for cultivation practices aimed at optimizing leaf area development. The substantial indirect effects between leaf area and chlorophyll content suggest synergistic interactions between these physiological traits, where improvements in one parameter may enhance the other's effectiveness. This physiological synergy likely contributes to the superior performance of varieties like Fozzie, which exhibits high values for both parameters.

Principal Component Analysis of Physiological and Performance Traits

Principal Component Analysis (PCA) was performed to identify major sources of variation among the ten gerbera varieties based on physiological and performance parameters (Figure 2, Table 4). Two principal components with eigenvalues greater than 1.0 were extracted, together explaining 78.4% of total variation. 2) clearly separated varieties into distinct groups based on their physiological and performance characteristics. Fozzie and Gonzo were positioned in the high PC1 region, indicating superior photosynthetic capacity. Camilla, Beaker, and Honeydew clustered in the low PC1 region, reflecting limited physiological development. This multivariate analysis confirms the central role of physiological traits in determining overall performance patterns among gerbera varieties.

Cluster Analysis and Physiological Classification

Cluster analysis using Ward's method classified the ten gerbera varieties into three distinct physiological groups (Figure 3 This physiological classification provides a systematic framework for varietal selection based on underlying physiological characteristics. The high-performance cluster (Fozzie and Gonzo) represents varieties with optimal physiological traits for polyhouse cultivation, while the lowperformance cluster identifies varieties that may require specific management interventions or may be less suitable for intensive production systems.

Physiological Basis of Superior Performance in Fozzie

The comprehensive physiological analysis provides insights into the basis of Fozzie's superior performance observed in our companion studies (Srujana et al., 2025a, 2025b) [9,10] . Fozzie's combination of high leaf area (109.06 cm²) and chlorophyll content (47.41 SPAD units) creates optimal conditions for photosynthetic efficiency and assimilate production. The strong correlations between these physiological traits and key performance parameters explain Fozzie's excellence across multiple dimensions: The physiological superiority of Fozzie is further evidenced by its position in the high-performance cluster and its high scores on PC1 (photosynthetic capacity) in PCA. These physiological advantages translate directly to commercial benefits, making Fozzie particularly suitable for intensive polyhouse cultivation where maximizing productivity and quality is paramount.

Implications for Breeding and Cultivation

The strong relationships between physiological traits and performance parameters identified in this study have important implications for gerbera improvement and cultivation:

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