Saturday, August 18, 2012

Blackberry Receptacles

Reaching through the thorny bramble, my fingers closed on the biggest, juiciest, blackberry I had ever seen. My pail was over half full, but this berry did not join the crowd, instead I popped it straight into my mouth. Sweet juice burst into every corner of my mouth. Yum!  I love berry season!

Berry season is a time for red fingers and purple tongues.  Not just blackberries, but raspberries, serviceberries, and blueberries all contain a pigment called anthocyanin, which can be red, purple, or blue depending on the acidity of the fruit.  In nature, pigments do not just provide color; they also carry out important functions.   Anthocyanin is useful to plants as a sunscreen, and to us as an antioxidant. 

In fact, blackberries’ antioxidant capacity ranks near the top of 1000 antioxidant foods consumed in the United States. They are also notable for their high nutritional contents of dietary fiber, vitamin C, vitamin K, folic acid (a B vitamin), and the essential mineral manganese. Blackberries even retain most of these health benefits through the process of making them into jam and storing them over the winter.

As my pail filled with blackberries (the goal of the day), my mouth often filled with red raspberries, too. These close cousins share the genus Rubus in the Rose Family. Have you ever noticed that when you pluck a raspberry off the plant, there is a little white dome left behind? The matching recess in the berry itself is the perfect size for capping little fingertips, or hiding sneaky bugs. Blackberries do not have that.  Their base is flat, and they pluck cleanly off the stem. There is a botanical reason for this.

Raspberries and blackberries begin with very similar flowers. They both have five white petals that surround an outer ring of many stamens (the pollen-producing part) and an inner cluster of pistils (the female part). All these parts are joined at the base in a structure that botanists call the hypanthium. The hypanthium, in turn, is attached to a flower stalk called the receptacle.

As a pollen grain lands on one of the many stigmas (the tip of the pistil), it travels down a pollen tube to fertilize the ovule (egg) in the ovary. The fertilized ovule becomes the seed, and the ovary develops into the juicy fruit. On raspberries, the top parts of the pistils remain as tiny hairs bristling out of each bump on the fruit.

Have you ever noticed how hard blackberry seeds are when they get stuck in your teeth? Each tiny seed is enclosed in a lignified (woody) case – just like the pit of a peach. The term for this type of a fruit is a “drupe.” Cherries are another good example of drupes.

As the many pistils in raspberry or blackberry flowers receive pollen, each ovary develops into a little drupe or “drupelet.”  The drupelets then fuse together into the many-dimpled raspberry we know and love. Thus, blackberries and raspberries are not berries at all, but “aggregates of drupelets.” True berries are simple (not aggregate) fruits that develop from a single ovary. Some examples of berries include avocados, bananas, blueberries, grapes, tomatoes, watermelons, and pumpkins.

The main difference between the two fruits I encountered in the thorny bramble is that in addition to fusing all the little drupes together, blackberries incorporate the receptacle (the base of the flower) into the fruit, while raspberries leave their little white cone of a receptacle still attached to the plant.

While botany fascinates me, at the end of the day, the only receptacles that I pay attention to are the full pail and my happy belly!

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, STAR POWER: Energy from the Sun, opened in May 2012 and will remain open until April, 2013. Find us on the web at to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot,

No comments:

Post a Comment