Trinity River Audubon Center - August 9, 2013

It is going to be another very hot day here - forecast high of 103 F.  When I arrive at 8:15 it is already 86. 

The pitfall traps continue to yield little.  The extreme heat over the last week (many 104 and 105 days) is causing rapid evaporation of the alcohol.  Last week I added about 10 ml of glycerol to a liter of propanol to see if that would slow down the evaporation.  In most traps all that is left is the glycerol.  I know that I need to check the pitfalls much more often .  Once my class starts if I have students who are interested in taking over the pitfalls we can work out a schedule for checking the traps more frequently.

I refilled the pitfalls and laid the tile cover right on the ground instead of having it suspended above the trap on pegs.  The ground in this area is very uneven so there is still plenty of space for insects and spiders to enter, and this may help with the evaporation problem.

Interestingly, the traps farthest from the water (9 m) captured the most organisms - mainly small ground beetles and very small spiders.

My fascination with wildflowers continues.  Despite what many folks may think, even in the extreme heat there are wildflowers blooming at TRAC.  The Partridge Peas (Cassia fasciculata) are going strong.  The student who was with me noticed that as the pea pods dry out they twist open to disperse the seeds.  The empty pod halves look very much like DNA helices.  I didn't get a photograph but will make a note to do so next week.

Lance-leaf Loosestrife (Lythrum lanceolatum)

A very small flower but very striking.  For scale notice that the length of my thumb nail just happens to be 1 cm.

 

Here is a close up of the flowers.  Notice the long stigma sticking out of the center of the petal and the dark purple line on each petal. 

 

The stems and roots of plants get longer by adding cells to their tips.  This area of cells is called the apical meristem.  This means that the youngest tissues are nearer the tips of the stems and everything gets older as you move down the stem.  On this flower you can see unopened flower buds on top and those that have been pollinated, lost their petals, and now hold developing seeds, below.  This leaves a band of blooming flowers, not at the top of the plant, but a few inches below.

 

Grassleaf Arrowhead (Sagittaria graminea var. platyphyla)

This is a water plant.  Because of all of the foliage I used weird colored arrows to help you locate the plants.  I found this plant right at the edge of a pond at TRAC in an area that was muddy, but not wet. I believe it was at the Dragonfly Pond. (I failed to make the proper notation in my field book - bad Murry!)



Here you can see the flowers each containing 3 petals, one of the hallmarks of a monocot.

As with the loosestife, you can clearly see the unopened flower buds at the top of the stalk and the swollen ovaries and shriveled-up petals on the pollinated flowers below.  the ovaries will become the seed pods.

 

 Sawleaf Daisy (Prionopsis ciliata)

The sawleaf daisies are finally begining to open in large numbers.  They are slow growers and slow bloomers, so I expect to be seeing them for several more weeks.  This composite "flower" is actually lots and lots of individual flowers grouped together.  The flowers in the middle are called disk flowers and have no petals.  The flowers around the edge are called ray flowers and have only a single petal each.

Sawleaf daisy with an unopened bud below.

The unopened flower has its ray flowers tightly packed into a yellow dome.  You can also see the spiked leafs that give this plant its name.

 The Maximillian Sunflower (Helianthus maximilian)



If you were to ask me what my favorite color is, I would probably never tell you yellow, but I will admit that I find sunflowers absolutely beautiful.  

Identification of this flower gave me fits.  The main reason being my assumption that the very long sepals seen in the image above would be diagnostic.  There weren't.  The leaves, on the other hand, are.  Notice they are folded into a V or trough and turn downward at the end.

In this image shows the leaves of the sunflower.  Also notice the leaf at the bottom left of the image has an insect gall on it.  (The shoes belong to a student.)

In this image you can see a gall and some aphids.  I did not observe it, but I suspect that the ants in the image were probably harvesting the honeydew from the aphids.  (By this time it was about 97 F and time for me to head back to the car.)

Funnel-Web Spiders

 

At the southeast end of the Great Egret Pond - which by the way had Great Egrets on it - if found some funnel-web spiders.   (The trail along the western edge of Whistling Duck Pond also has many of these webs.)





The arrow in this image shows the spider in the neck of the funnel - its retreat.

I couldn't help aggrevating the spider until it came out of its retreat.  Notice also that this spider had molted - its old skin is indicated by the arrow on the right of the image.  I did collect this spider so there will be some additional images later.

Another very good day at the Trinity River Audubon Center. Most of the time I feel like a kid in a candy shop - so many interesting things to choose from.    Interestingly, lots of people who visit the Audubon center are there to look at birds.  In my case, I spend most of my time looking down instead of up.

 

All images are under a Creative Commons license.  You are welcome to copy, retransmit, and modify these images all you want, but need to identify their source as Eastfield College, Mesquite, TX. 

Murry Gans

Microscopy Lab Coordinator

Eastfield College

 

Cyperus retrorsus - The Cylindric Sedge

 

Trinity River Audubon Center - July 26, 2013

When I first saw this plant at TRAC what caught my eye were the burr-like structures.  Taking a closer look revealed something unexpected - a triangular shaped stem - an identifying charactersitic of sedges.  As I was told by Ron Beecham, a professor of Biology here at the college, "Sedges have edges."

Here is a detailed look at the Cylindric Sedge (Cyperus retrorsus)



A photo from the field.  I have memories of running barefoot as a young boy and stepping on rather large cockleburs.  When I took a closer look what I found was not the stickery fruit of the cocklebur, but the typical, incomplete flower of a grass.

A photo from the field showing the flowers of the sedge.

I took a specimen back to the lab for more photos and for examination under the dissecting scope and the scanning electron microscope.

This photo shows the flowers of the sedge.  (Anyone familiar with the 3rd floor of the C Building at Eastfield College will probably recognize the patio where I took this photo.)  Also notice the three-part symmetry, typical of monocots.

In this photo you can see the multi-part flowers and even some of the anthers hanging out of the flowers. 

If you haven't studied botany, or have forgotten what you knew when you took it, it may seem a little confusing for me to use the term flower.  Where are the petals?  Lots of plants produce flowers without petals.  This includes most trees, grasses, and, in this case, sedges. 

 

Complete flowers contain all four of the major floral parts: sepals, petals, stamen -the male parts that produce the pollen, and the pistils or carples which contain the eggs.  We are most familiar with complete flowers and love their colorful, showy petals.  But there are also incomplete flowers which are missing one or more of the floral parts.  Grasses and trees often don't have petals, but they still reproduce sexually, just like those roses you may have given or received on special occasions.

 

A flower is the reproductive structure of a plant.  Some flowers contain both male and female reproductive structures on the same plant and are called monoecious (Greek for "one house").  Other flowers contain male or female structures on different plants are are said to be dioecious ("two houses").

This sedge has monecious, incomplete flowers.

Here is a closer look using the dissecting scope in the lab.

I brought the sedge back to the lab, put the stem in water and left it in the window over the weekend.  This little bug didn't seem to mind at all that the sedge was no longer outside.  It was happily crawling around and munching pollen.

Here you can get a sense of the structure of these flowers.  They are made up of overlapping segments with anthers and stigmas sticking out.  The white arrows in this picture indicate anthers.

 


Here is one section showing the structure. Each segment is a flower  and

has an anther and stigma and will produce a single seed.

The  next images were made with the scanning electron microscope. 

 

This structure is pretty small, only about 5 mm or about 1/4 inch long.  Each overlapping segment is a separate flower.

[40x]

 

At 200x you can see lots of details.  The anther has split open and spilled out its pollen and you can see the stigma.  (Unfortunately, the electron microscope dries out structures very quickly, so the pollen grains and cells of the stigma are collapsed.)  Even though these are the reproductive structures of the plant, they are still green and photosynthetic so they need to take in carbon dioxide and and release oxygen.  That is why you see stomata here. 

 

For this image I have turned the structure on its edge to show an anther hanging off.  These are actually visible with the naked eye and you can find them on the St. Augustine and Bermuda grass in your yard. [56x]

Same anther at 150x.  Here you can see it is split open and has pollen spilling out.

Several anthers at 190x.  Turns out it is very easy to cause these to fall off of the plant.  I shook the plant over my mounting stub to collect pollen and also found these. 

Anther with pollen at 300x.



Pollen grains at 1,700 x magnification.

The software on the scanning electron microscope allows me to make very precise measurements.  As shown in the image at 1,700x the pollen grain is only 22.61 microns x 29.90 microns.



I have to admit that I am very pleased with this image.  It shows the detail on a pollen grain at 5,000x magnification. 

Of course, the purpose of all of this structure is to make seeds.  Once the pollen falls on the stigma of the flower and fertilization occurs the seed will develop.

This image from the dissecting scope shows a couple developed seeds. Notice that the flowers are larger on the bottom of the structure because they develop first and are older.

I have pulled back the covering to show the seed underneath.  You can see the stigma still attached to the top of the seed.



The seeds on under the dissecting scope.  These are very small.  Notice the scale bar showing 500 microns or 1/2 mm.

65x magnification on the scanning electron microscope.  The total length of this seed is less than a millimeter.

Another seed for comparison. 

A close up of the attachment of the stigma to the seed.  350x

What about those triangular stems?  Here they are.

This is a cross section of the triangular stem.  Notice that the green, photosynthetic cells penetrate deeply into the stem.



Same view as above on the scanning electron microscope.  14x

Dissecting scope view of edge of stem.

Electron microscope view of stem edge. 230x

Electron microscope view of stem edge. 936x

 

More than 40 years ago my biology teacher at Borger High School, Mrs. Eve Wyles, taught me that you can always tell the cross-section of a monocot plant because the bundles of vascular tissue resemble monkey faces.  "Monocots have monkey faces."

 

This sedge is definitely a monocot.

 

Bundles of xylem and phloem,  monkey faces, indicated with arrows.  70x

More monkey faces.  130x

This one is for you, Mrs. Wyles.  450x

I really love going into the field each week and never know what will grab my interest.  I seem to learn something new every time.  Sedges?  Why not.

Please do not hesitate to contact me if you have comments or questions about this posting.  All images may be used, downloaded, or modified as long as you give credit to Eastfield College, Mesquite, TX. 

Murry Gans