Study of an inflorescence, or…from flower to seed
1. the plant observed :
Begonia garagarana C. de Candolle is a plant of section Gireoudia found in Panama.
Easy to grow, this shrub-like begonia with upright stems reaches a height of about 60 cm.
The development of the inflorescence was observed over almost 3 months (73 days exactly), from 2 February, when the 1st flower bud appeared, to 16 April, when the first fruits – and therefore seeds – were harvested.
2. the inflorescence : in this species, the inflorescence is a biparous cyme (or dichasial inflorescence)
- it is a cyme, i.e. an inflorescence in which every apex (tip) produces a flower.
- it is biparous which means its branches are arranged in opposite pairs.
- the bracts : modified leaves attached at the base of an inflorescence peduncle, which wrap the flower bud as it forms; in this species they are caducous (they fell very quickly, from the 3rd day after the flower bud appeared).
- the peduncle – the main one – of the inflorescence: it grew (reaching 26 cm for the longest) until the first flowers opened.
- length of the peduncle:
| date |
D (days counted from 2 February) |
length of the
peduncle in cm |
| 03/2 | +1 | 7 |
| 07/2 | +4 | 12 |
| 09/2 | +6 | 14 |
| 17/2 | +14 | 18 |
| 23/2 | +20 | 22 |
| 25/2 | +25 | 26 |
- during its development, the peduncle divided 4 times into 2, then once – the last time – into 3
- the length, diameter and angle of the two peduncles formed decrease at each division:
 |
| division | length cm | diameter mm |
| 1 | 3 | 4-5 |
| 2 | 2,5 | 2-2,5 |
| 3 | 1,5 | 1-1,5 |
| 4 | 1 | 0,5-0,6 |
| 5 | 0,5 | 0,2-0,3 |
3. number of flowers in the inflorescence:
- after 4 divisions into 2, then one into 3, the last branching point gives a “mini-inflorescence” made up of two lateral groups of 2 or 3 flowers (usually 2 female flowers and 1 male, sometimes 1 female and 1 male, and rarely 1 female for 2 males) and a single central flower, always male
- the single male flower between the two groups of 3 is the first to open
- the total number of flowers on an inflorescence is about 80: 50 female and 30 male
- the plant produced about ten flower stalks, giving around… 800 flowers!
4. pollination: a few female flowers were pollinated by hand, in 4 sessions
5. timeline:
| date | D | flowers | photo |
| 2 February | D0 | flower bud appears | |
| 03 | D + 1 |  |
|
| 07 | D + 5 |
|
|
| 17 | D+15 |
|
|
| 23 | D+21 |
|
|
| 3 March | D+29 | first (intermediate) male flowers open |
|
| 04 | D+30 | ||
| 09 | D+35 |
|
|
| 13 | D+39 | the male flowers keep opening, the female flowers swell |
|
| 14 | D+40 | the female flowers open (pollination 1) |
|
| 15 | D+41 | the plant is in full flower, with about ten inflorescences | 
|
| 17 | D+43 | the male flowers start to drop (pollination 2) |
|
| 19 | D+45 | all the flowers are open (pollination 3); the female flowers
are open from 9 am to 4 pm |
|
| 20 | D+46 | almost all the male flowers have dropped (pollination 4):
the tepals of the pollinated female flowers start to drop |
|
| 21 | D+47 |
|
|
| 26 | D+52 | the ovaries of the pollinated flowers swell |
|
| 1 April | D+58 | they are still swelling; the stigmas are still present |
|
| 10 | D+67 | same / beaks still present; unpollinated flowers drop |
|
| 16 | D+73 |
the fruits are ripe; they dry out and the seeds escape and scatter; dehiscence through the lateral slits is clearly visible; the beak (remains of the pistil) is still present. |
|
The next study will observe the development of the inflorescence of a plant of the type uniparous cyme.