Plants & Human Affairs - Introduction

Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Gink: and Go: at Lunch

Setting: Gink: and Go: are enjoying a meal in the Refectory. Go: has a fruit salad containing watermelon balls, blueberries, pineapple chunks, some grapes, and slices of orange, strawberry and apples. Go: also has a green bean salad sprinkled with sunflower seeds, peanuts, and walnuts. Gink: has a hot dog on a wheat bun lathered with mustard, a pile of French fries with catsup, fig cookies and a banana split.

Gink:		Hey Go, how’s your lunch?
Go:		Great – especially now that I know what I’m eating. I really enjoyed learning all about fruit types in Saupe’s biology class.
Gink:		I thought it was boring. It just made me hungry so quiet down so I can finish my tube steak.
Go:		I have an idea, let’s see if we can identify the types of fruits in our lunch.
Gink:		Oh please – let me just enjoy my meal in peace without having to think about that stupid class.
Go:		Come on – it’ll be fun. Check out my fruit salad – I’m eating a pepo, berries, hesperidium, pome and even an aggregate of achenes
Gink:		Which are the berries – are they the fruits with the dehiscent pericarp?
Go:		Don’t you remember, berries are simple, indehiscent fruits with a fleshy pericarp.
Gink:		They’re indecent?
Go:		Not indecent, indehiscent! It means that they don’t open up to release the seeds.
Gink:		I knew that – just joking. So the blueberries and grapes are berries, right?
Go:		Of course – even you are eating some berries.
Gink:		No way – I avoid healthy stuff like that
Go:		The catsup is made from tomatoes which are berries. And beneath that wad of ice cream is another berry.
Gink:		Not the banana?
Go:		You bet.
Gink:		But where are the seeds?
Go:		Commercial bananas don’t produce seeds. The fruits are parthenocarpic – that is, they develop without fertilization. The little black spots inside are the ovules that never developed.
Gink:		Cool – but how do they reproduce?
Go:		The plants are propagated asexually by cuttings. And, by rhizomes.
Gink:		Enough about bananas. I sure hope I’m not eating any other fruits
Go:		Of course you are! Silicle, synconium, and caryopsis or grain are some other fruits you have there.
Gink:		Is the fig a silicle? It seems silly to me.
Go:		Nope. Figs are a synconium, a type of fruit that has a hollow receptacle lined with imperfect flowers. The hollowed receptacle has an opening in the top called the ostiole.
Gink:		If the flowers are locked away inside of a chamber, how do they get pollinated?
Go:		Fig wasps.
Gink:		Huh?
Go:		Yeah, wasps enter the opening and forage around inside the fig. They have a very interesting co-evolutionary relationship.
Gink:		So if the flowers are imperfect, then are the plants monoecious or dioecious?
Go:		Good question. Some figs are monoecious and have pistillate flowers with both long styles and short styles interspersed with staminate flowers. Other figs are dioecious. In these, one plant has figs with pistillate flowers that have long styles and on other plants are figs that have pistillate flowers with short styles and staminate flowers. The staminate flowers are usually near the ostiole.
Gink:		Why styles of two different lengths?
Go:		To protect the ovules. The ovipositor of the female can’t reach the ovary of the long-styled flower to deposit her eggs
Gink:		Cool. Does that mean I’m eating dead bugs in my figs?
Go:		In some. Mission figs produce fruits without the need for pollination but other types, like Smyrna figs need male and female plants. Caprifigs are the male plants.
Gink:		Holy Fig Newton. So what’s this silique I’m supposed to be eating?
Go:		Actually you’re not eating the silique but the seeds from a silique – mustard.
Gink:		Really?
Go:		Yup. Mustard is prepared from the seeds that develop in a silique. These fruits are simple, dry and dehiscent. When the halves of the fruits dehisce they expose the seeds and a translucent partition.
Gink:		Like a money-plant pod. I know the difference between a silique and silicle. A silique is long and slender but a silicle is "silly" – just like Santa Claus who is short and round.
Go:		Right. And the caryopsis produces the bun. Wheat, corn, rye, oats, and other grasses produce a fruit called a caryopsis or grain. This type of fruit is single-seeded and the seed coat is fused to the pericarp.
Gink:		Seeds must get cold if they need a coat.
Go:		No, the seed coat is produced from the integument of the ovule to protect the embryo.
Gink:		Lighten up. It was another joke. I knew that and I even know that a caryopsis is similar to an achene that is also a simple, dry, indehiscent fruit. The main difference is that the seed of an achene is only attached to the pericarp in a single area called the funiculus.
Go:		You always amaze me. The sunflower seeds in my salad come from an achene. And look at the samaras on the maple tree in the courtyard, they are essentially winged achenes.
Gink:		Yup. And your strawberry is a collection of a bunch of achenes.
Go:		Right again. It’s an aggregate fruit that came from a single flower with numerous carpels.
Gink:		The flower had an apocarpous gynoecium.
Go:		That’s right smarty pants, but how does it differ from a multiple fruit like this pineapple?
Gink:		Pineapples are juicy fruits. You know, like they use to make gum.
Go:		Funny. Multiple fruits are derived from ovaries in many flowers. As they develop the ovaries fuse together. It’s easy to see on a pineapple. Each of the different sections represents a flower. You can even see the bracts.
Gink:		But where are the seeds?
Go:		This is another parthenocarpic fruit.
Gink:		Who cares? Let’s finishing eating so I don’t fall asleep in class as usual.

Last updated: 10/24/2005 / � Copyright by SG Saupe / URL:http://www.employees.csbsju.edu/ssaupe/index.html