Evaluating the combined effects of light and water availability on the early growth and physiology of Tamarindus indica: Implications for restoration

Abstract

Premise: The tamarind tree (Tamarindus indica) is a species of significant cultural, economic, and ecological value, with a pantropical distribution. However, the tamarind is experiencing a decline in wild populations in its native range, but the reasons for its decline remain unknown.

Methods: We examined the critical early life-history stages for tamarind establishment to understand how varying levels of light and water availability and watering frequency affect its regeneration. Through three greenhouse experiments, we assessed the impact of these resources on the germination, survival, growth, and physiological responses of tamarind seedlings and saplings.

Results: Water availability was critical for seed germination, but not light levels or pre-germination treatments. Light was the primary limiting factor for seedling growth. Tamarinds in high light availability grew taller, had more biomass and larger diameter, but the effect of light was modulated by water availability, indicating that there was an interaction between both resources. Water and light affected specific leaf area and leaf dry matter content but not biomass allocation, root-to-shoot ratio, or stomatal conductance. Water availability influenced sapling growth, but watering frequency did not, indicating a resilience of tamarind saplings to changes in rainfall periodicity but a sensitivity to total rainfall amounts.

Conclusions: Our study underscores the importance of considering both light and water availability in tamarind restoration efforts and contribute to understanding plant responses and trade-offs under different levels of critical resources. Our findings will inform conservation strategies to support the regeneration and long-term survival of Tamarindus indica in its native habitats.

Keywords: Fabaceae; Tamarindus indica; light; resource availability; restoration; seed germination; seedling growth; trade‐off hypothesis; watering frequency.

Figure 1

Tamarind seed germination percentages at 30 days post treatment among the different light and watering levels for scarified or intact tamarind seeds. Bars represent the total germination percentage for each treatment combination. Different colors in the bars represent the seeds that were or were not scarified before sowing. The statistical tests were conducted on the binomial responses of germination (germinated or not germinated) plots show germination percentages for clarity.

Figure 2

Tamarind seedling dry biomass in three light and four watering levels. Low light: 9 μmol m⁻² s⁻¹, medium: 120 μmol m⁻² s⁻¹; high: 970 μmol m⁻² s⁻¹ (all at midday). Low water: 210 mL, medium: 845 mL, high: 1690 mL. Different letters above the bars denote differences with strong statistical support (post hoc Games–Howell test, P < 0.05).

Figure 3

Tamarind seedling stomatal conductance (A) and stomatal density (B) under three light conditions and three watering levels. Low light: 9 μmol m⁻² s⁻¹, medium: 120 μmol m⁻² s⁻¹; high: 970 μmol m⁻² s⁻¹ (all at midday). Low water: 210 mL, medium: 845 mL, high: 1690 mL. Different letters above the bars denote differences with strong statistical support (post hoc Games–Howell test, P < 0.05).

Figure 4

Tamarind sapling height within (A) each watering treatment (total weekly volume: low, 210 mL, medium: 845 mL; high, 1690 mL) and (B) for the different watering frequencies (845 mL every 3 days). Different letters above the bars denote differences with strong statistical support (post hoc Games–Howell test, P < 0.05).

Figure 5

Tamarind sapling root‐to‐shoot ratio within (A) each watering treatment,(total weekly volume: low, 210 mL, medium: 845 mL; high, 1690 mL) and (B) for different watering frequencies. Different letters above the bars denote differences with strong statistical support (post hoc Games–Howell test, P < 0.05).