Instituto de Ecologia, A.C. Xalapa, Veracruz, Mexico. C.P. 91070f Early Growth of Ramon (Brosimum alicastrum Sw.) and Relationships Between Seed Weight and Seedling Size Anibal Niembro Instituto de Ecologia, A.C. Xalapa, Veracruz, Mexico. C.P. 91070f

Brosimum alicastrum Sw. First, let me begin by introducing you to brosimum alicastrum. This tropical tree is native to the yucatan peninsula in mexico has great potential for agroforestry in that area. Because of this potential, tropical forest nursery managers want to maximize the number of healthy, vigorous seedlings they produce from any given seed lot. For many temperate tree species, one way to do this is to size the seeds and plant the heavier seeds.

Heavier Seed = Larger Seedling? Faster germination Greater vigor Greater growth potential Morphological uniformity The effect of heavier seeds on seedling morphology has been examined by many authors. Often, heavier seeds germinate faster, result in seeds with greater vigor and growth potential than smaller seeds, and have greater morphological uniformity. Currently, our knowledge of the germination characteristics of many tropical species is scarce. The goal of this research then was to evaluate the emergence rate and early seedling growth of ramon seeds, and to explore the relationship between seed weight and seedling growth.

Materials and Methods Collection of bulk sample 200 randomly chosen seeds Seeds were weighed and planted In 1997, a bulk sample of mature, open pollinated fruits was collected in the state of Campeche, Mexico. Seeds were manually removed from the fruits and cleaned. From this sample, 200 seeds were randomly chosen and weight to obtain their fresh weight. After weighting, seeds were randomly sown in polyethylene containers in a shaded greenhouse; these seeds were watered throughout the course of the experiment.

Materials and Methods Growth was measured by monitoring: Emergence rate Seedling height Main root length Stem diameter Number of leaves Stem and leaf fresh and dry weight Root fresh and dry weight Sturdiness quotient Shoot/root ratio Growth was measured by monitoring emergence rate, seedling eight, main rot length, stem diameter, number of leaves, stem and leaf fresh and dry weight, root fresh and dry weight, the sturdiness quotient of the seedlings (which is a measure of the stocky or spindly nature of the seedling) and the shoot/root ratio (which is a measure of the balance between transpirational area and water absorbing area).

Materials and Methods Descriptive statistics: Mean, standard deviation, standard error, 90% CI, minimum and maximum values, and the range of coefficient of variability. All of these variables were statistically examined in 2 ways: All variables were descriptively analyzed for their mean, SD, SE, 90% CI, minimum and maximum values, and the range of the coefficient of variability. In order to look at the relationships between seed weight and the measured variables, correlation analysis was used. Correlation analysis Relationship between seed weight and other variables.

Results & Discussion – Seed Weight and Emergence 184 seeds germinated Seed weight ranged from 0.65 – 6.02 g Emergence began 12 days after sowing and continued for 27 days; average time to germination: 17.8 days Of the 200 seeds planted, 184 germinated. Of those 184, seed weight ranged from 0.65 to just over 6 grams. Emergence began 12 days after seeds were sown and continued for 27 more days. Average time to germination of the seed lot was 17.8 days.

Results & Discussion: Seedling Growth and Development After 50 days seedlings displayed great morphological differences. As you can see from this table, for all measured variables there was a great difference between the minimum and maximum values. For example, height ranged from 8.6 to 35.5 cm and stem diameter from 1.3 to 6 mm. The sturdiness quotient, which to remind you is the measure of the “build” of our plants, ranged from 4.53 to 18.1 cm, indicating a highly variable seedling morphology. There was also a large range in the shoot/root ratio values; this large range indicates that there were seedlings without an appropriate balance between absorption and transpirational area.

Results & Discussion: Correlation Analysis Heavier seeds did tend to germinate faster (P<0.01) Earlier germination = head start = large differences in seedling size and weight. The correlation analysis found a significant negative association between fresh seed weight and emergence time, indicating the tendency of heavier seeds to have more rapid germination. This earlier germination date for some of the seeds explained why the resulting plants showed such notable differences in size and weight.

Results & Discussion: Correlation Analysis

Summary This experiment found that fresh seed size did effect emergence rate and the growth of B. alicastrum seedlings. Selection and planting of medium to medium large seeds is recommended for nursery production.