Research work on the improvement and breeding of indigenous hardwood species in Nigeria started about four decades ago. Such studies prove to be fruitful in planning various conservative programme specific to different habitats. The present preliminary study focuses on the flowering and fruiting pattern of a 5 year old Afzelia africana artificial forest at Eastern Research Station, Umuahia, Abia State, Nigeria. The parameters observed were phenology, flowering intensity, floral biology, fruit set and floral visitors. Flowering was first observed in 2012 (three years after planting) and subsequently in 2014 (five years after planting), although no fruit was set until 2014. All the processes of flowering to fruiting took place between January to August, with flowering peak occurring in March. The flowering intensity was very low, ranging among 286, 138, and 54, with a very low flower to fruit ratio. It is presumed that the relative young age of the trees and reduced population size amongst other probable factors may have accounted for this observation. This study is the first record of flowering and fruiting pattern of this species at plantation level in Nigeria. By late July/August, matured fruits were ready for harvest.
Afzelia Smith is a small tropical genus belonging to the family Caesalpinaceae. It is represented in Nigeria by four tree species: Afzelia pachyloba, Afzelia bipindensis, Afzelia bella and Afzelia africana. The species, Afzelia africana Sm (Counter wood tree) understudy is commonly found in the Savanna fringing forests and drier parts of the forest region in Nigeria [
A relative number of studies on reproductive biology of tropical species from natural forest ecosystem has been reported by some authors [
The Forestry Research Institute of Nigeria, Eastern Research Station, Umuahia, Abia State, Nigeria, lies on latitude 5˚32'N and longitude 7˚29' along Umuahia/Ikot-ekpene road, Umuahia, at an altitude of over 122 m above sea level (
The mini-plantation of A. africana was established in 2009 at an espacement of 5 m by 5 m (0.5 hectare) from seedlings raised from seeds in the nursery unit. Phenological observations on stages of flower development from flower bud initiation to anthesis were carried out in the five year old plantation. Though initial observation of flowering occurred in 2012 (three years after planting) with complete abortion of all flowers recorded.
Observations were made weekly on selected three tagged flowering trees of A. africana in the site. The parameters observed were as follows:
a) Timing and duration of flowering
The commencement and termination of flowering among the sample trees of A. africana were noted.
b) Estimation of flowering intensity
This refers to the quantity of flowers produced by a tree per unit time, and was estimated for each of the three flowering trees selected. For each of the trees, the following parameters were recorded:
i) Total number of branches per tree
ii) Total number of branches carrying flowers/tree
iii) Total number of twigs/branch
iv) Number of twigs having flowers/branch
v) Number of twigs without flowers/branch
vi) Total number of spikes/10 twigs
vii) Total number of florets/10 spikes
c) Floral biology
The length and width of the flower buds were noted. Number of filaments, length of filaments and length of anther were measured. Length of sepals, petals, style and pedicel were also registered.
d) Identification of floral visitors
During the flowering period, the sample trees were observed for floral visitors, purpose of visiting and interaction with flowers were properly recorded, captured and identified.
e) Observation on fruit set
Commencement of fruiting as well as the developmental changes of the fruits till dehiscence was monitored. Fruit length, width and breadth; pedicel length and changes in fruit colour with maturity were all registered. Number of seeds per fruit as well as seed length and width were also noted.
The average height of the trees studied was 2.0 m with an average diameter (DBH) of 0.7 m. The average crown diameter was 3.2 m, not too dense, but had large irregular branches (
three fruits were set on one tree out of the three trees studied, indicating very low flower to fruit ratio. By late July to August, the matured fruits were dehisced, ready for seed dispersal. This was the first record of fruiting by the tree species since establishment of the mini-plantation.
The total number of florets (flowers) per tree varied among the three tagged trees examined within the study site. Tree II had the maximum of 286 while tree III had the least value of 54 as shown in
The floral traits of A. africana as observed in this study are presented in
Details of fruit set are presented in
Sample Trees | |||
---|---|---|---|
Parameters | Tree I | Tree II | Tree III |
Bn | 2 | 6 | 3 |
BFn | 1 | 4 | 1 |
T/B | 18.5 | 2.5 | 3.6 |
TF/B | 4.5 | 1.2 | 2.3 |
T-F/B | 14.0 | 1.3 | 1.3 |
S/T | 6.6 | 95.2 | 11.7 |
F/S | 23.3 | 3.1 | 3.6 |
Fn/T | 138 | 286 | 54 |
Keys: Bn = Total number of branches per tree; BFn = Number of branches carrying flowers per tree; T/B = Total number of twigs per branch; TF/B = Number of twigs having flowers per branch; T-F/B = Number of twigs without flowers per branch; S/T = Total number of spikes per 10 twigs; F/S = Total number of florets per 10 spikes; Fn/T = Total number of flowers per tree.
Parameters | Observations (cm) |
---|---|
Average number of filaments | 7.0 |
Average length of filaments | 3.0 |
Average length of anther | 0.2 |
Average length of sepals | 1.8 |
Average width of sepals | 1.2 |
Average length of petals | 3.6 |
Average width of petals | 2.3 |
Average length of style | 3.8 |
Fruit/Seed Attributes | Range (cm) | Mean (cm) ± S.E. |
---|---|---|
Fruit length | 12.5 - 14.5 | 13.47 ± 0.54 |
Fruit width | 7.0 - 8.5 | 7.83 ± 0.50 |
Fruit thickness | 2.5 - 4.5 | 3.5 ± 0.60 |
Pedicel length | 6 - 15 | 9.7 ± 1.25 |
Number of seed | 5 - 8 | 6.3 ± 0.72 |
Seed length | 2.5 - 3.3 | 3.1 ± 0.24 |
Seed width | 1.2 - 1.7 | 1.5 ± 0.22 |
S.E. = Standard Error.
appearing black, thick-walled with woody pod (
The flowers were visited by bees, butterflies, grasshoppers and cored bugs. Bees and butterflies more frequently visited the flowers in the morning. Bright colour and odour of flowers attracted the pollinators towards the flower after anthesis. Occasionally, it was observed that ants, houseflies, and grasshoppers also visited the flowers towards the afternoon. Leaf defoliation was observed on the trees and could be linked to the activities of the grasshoppers. However, on the basis of visitation rates, it could be affirmed that honey bees and butterflies were the effective pollinators of the plants. Pictures of some of the floral visitors are presented in
The most crucial stages in the life cycle of any plant include reproduction, dispersal of seeds, germination followed by seedling establishment [
verse pollinators.
Pollen production in a plant depends upon several factors including season, anther length, pollen grain size and mode of anther dehiscence [
The earlier maturity period of A. africana in this study as compared to a similar study conducted in Ibadan, Oyo State, Nigeria by [
This preliminary investigation reveales that A. africana flowers biennially in Umuahia, with flowers obtained between March and April. The flower anthesis was observed between 9.00 GMT and 12.00 GMT. The flowering intensity was low with a very low flower to fruit ratio. Fruit set began by March and matured fruits were ready for harvest from late July to August, thus the appropriate time for seed collection for storage. Our study revealed the presence of some floral visitors like bees, butterflies, cored bugs and grasshoppers. The low fruit set in this species strongly suggest the requirement of some external agents necessary for effective pollination. Since this report is preliminary, subsequent investigation on the reproductive biology of this species in this area over time is suggested. This is important because the evolutionary success and survival of this tree are largely determined by the efficacy of its reproductive performance.