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

Mondragon, Ariadna 1 ; Powers, Jennifer S.1

Research facility: University of Minnesota

Published Mar 04, 2025 on Dryad. https://doi.org/10.5061/dryad.xwdbrv1q8

Data files

Mar 04, 2025 version files 113.46 KB

README.md

18.69 KB
Tamarind_germination.xlsx

12.42 KB
Tamarind_saplings_growthv2.xlsx

33.23 KB
Tamarind_seedling_growth.xlsx

49.12 KB

Abstract

Premise: The tamarind tree (Tamarindus indica L.), 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 or 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 a higher biomass and a larger diameter, but this effect 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 inform conservation strategies to support the regeneration and long-term survival of Tamarindus indica in its native habitats.

https://doi.org/10.5061/dryad.xwdbrv1q8

Description of the data and file structure

Tamarindus indica seed germination and early growth

This dataset contains three files with the results of three greenhouse experiments designed to assess the impact of two critical resources, light and water, on the germination, survival, growth, and physiological responses of tamarind seedlings and saplings.

The file "Tamarind germination" contains the data of the first experiment designed to evaluate the germination responses of tamarind seeds under varying light and water conditions. We sowed 300 seeds in germination trays filled with Sungro Professional Growing Mix, positioning them approximately 5 mm below the surface. The seeds, with an average mass of 1.05 g, were distributed across three light treatments—low, medium, and high light—created using shade houses of PVC pipes and shade cloths to simulate forest-like conditions. The light intensities were measured in terms of photosynthetic photon flux (PPF) and varied as follows: full light at 970 μmol m^{−2 s}−1 (open forest areas), medium light at 120 μmol m^{−2 s}−1 (small forest gaps), and low light at 9 μmol m^{−2 s}−1 (closed canopy). Seed germination was monitored for 30 days post-sowing to determine the effects of light, water, and scarification treatments on germination rates.
The file "Tamarind seedling growth" presents the data of our second experiment that was designed to assess how different levels of light and water influence the growth and survival of tamarind seedlings. This experiment involved 300 tamarind seedlings grown in a full factorial design, combining three light levels (as established in Experiment 1) with four different watering regimes. The seedlings were sourced similarly to those in the first experiment, with an average seed mass of 1.06 g. Each light treatment had 100 seedlings. These seedlings were classified as plants younger than three months that had not yet dropped their cotyledons. Within each light category, seedlings were subjected to one of four watering treatments—no water, low, medium, and high—distributed evenly across 25 seedlings per light and water combination. Seedlings were planted in 1-gallon pots using a soil mix of 40% black soil, 30% sand, and 30% composted pine bark, and fertilized with 23 grams of slow-release Osmocote Plus (15N:9P:11K). Over four months, measurements were taken weekly to track seedling survival, stem diameter, and height. At the experiment's conclusion, seedlings were harvested and their fresh and dry biomass was measured. This biomass data is contained in the file.
The file "Tamarind sapling growth" has the data which explored the influence of water availability and watering frequency on the early growth of tamarind saplings. In this experiment, a total of 150 tamarind saplings, cultivated from an independent batch of seeds, participated in this experiment. These saplings were defined as such due to their age of six months, woody stems, and absence of cotyledons. Initially, all saplings were grown under uniform conditions in one-gallon pots containing a mixture of 40% black soil, 30% sand, and 30% composted pine bark, fertilized with 23 grams of Osmocote Plus. They received a consistent initial watering regime of three times per week for the first three months. After three months of uniform growth conditions, the saplings were distributed into four different watering treatments, each comprising 25 plants. These treatments mirrored those used in Experiment 2 (no water, low, medium, and high watering). Alongside the standard treatments, two groups of saplings within the medium watering category were subjected to varied watering frequencies:
- Group 1: Received the total weekly water allotment in a single weekly session.
- Group 2: Water was distributed bi-weekly, ensuring the same total weekly volume as Group 1 but administered less frequently.
These treatments lasted for three months. At the end of this period, all saplings were harvested, and detailed assessments were conducted to evaluate their growth and physiological traits, focusing on how water stress and frequency of watering influenced sapling development.