Field Guide of Discovery-based Exercises for - Aseanipm ...

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Field Guide of Discovery-based Exercises for Organic Vegetable Production
a) Studying Crops’ Biological Processes and Hybridization Exercises for String Bean
Biological Processes of String Bean:
5 Study plant morphology and growth stages (e.g., duration of and changes in morphological
structures at different growth stages).
5 Study flower morphology (e.g., type and parts of flower, duration of stigmatic receptivity
and anther dehiscence, pollination and emasculation procedures, etc.).
5 Study flower and fruit setting (e.g., number of flowers for pollination and fruits that set
after pollination).
5 Take note of all relevant observations and experiences during this activity.
Emasculation of String Bean Flowers (Female Parent):
5 Select varieties to emasculate in learning field. Choose flower buds that have reached their
maximum unopened size, started to pale slightly, and are to open the following morning.
Select the first developing bud on raceme for crossing, which tends to set, pods more easily
than later developing buds. Remove other buds to divert all nutrients in peduncle into one
pod increasing success rate and to avoid confusion in labeling;
5 Hold selected bud for emasculation firmly but gently to avoid any stress at fragile attachment
of bud and raceme. Using small scissors, or even long thumbnails, make a cut at center of
bud starting from its straight edge. Cut about two-third the width of unopened bud, taking
care not to damage enclosed style and stamen.
5 Grasp upper portion of folded petals by thumb and index finger and gently tear-off cut
segment, leaving upper portion of style, stigma, and stamens free and exposed. Remove
10 anther sacs with small scissors, taking care not to touch receptive green-tipped stigmatic
surface.
5 Repeat emasculation process using other flowers.
5 After completing emasculation, record number of emasculated plants in a crossing table,
as shown in example below:
Parent Materials
Mother
Plants
(Female
Parent)
Father Plants (Male Parent) No. of
Variety 1 Variety 2 Variety 3 Variety 4 Crosses
Variety 1 3 4 7
Variety 2 3 3
Variety 3 3 3 6
Variety 4 4 4