Black rust

Black rust is a disease that only occurs on wheat. It is caused by a fungus, Puccinia graminis. Puccinia is a genus of the order of the Rusts (Uredinales). The telia, in which the teliospores* are formed, are black. There are also other rust diseases, such as the yellow and brown rust, but the black variant is the most aggressive. The first sign that wheat has been contaminated with it, is a type of red, rusty blisters on the stem. Then the wheat grains shrivel, the stem bends, and eventually the plant dies and turns black.

A common pest

Rosebay willowherb or Fireweed - Chamerion angustifolium - is a very striking and widespread plant species. During flowering it is easy to recognize. The upright plants have a cluster-shaped inflorescence at the top that tapers to a point. The color of the flowers is purple or purple-red. The separate flowers in the cluster are somewhat symmetrical on both sides because the top two petals are somewhat smaller than the bottom two. The scattered leaves are narrow and lanceolate and closely resemble the leaves of Willows.

Just a beautiful preparation

Here we see the images of a beautiful preparation made by Mike Smith. The cross section trough the ovary of Buddleia globosa shows many details. Note that the ovary (and later the seed capsule) is covered in tangled hairs (stellate-tomentose) and how the base of the style is also hairy. The second fluorescence image shows this in detail.

Image stacking - for increased depth of field

A microscope is not only useful when investigating microscopic specimens. To see the fine details of insects and other larger specimens, a microscope is also extremely handy. However, the depth of field (DOF) is very shallow and only a small portion of the specimen can be in focus at each time. This is not due to bad objectives or microscope, but due to the high magnification. But this problem can easily be overcome by the use of an image processing method called focus stacking.

Illustration of the shallow depth of field.
The focus plane is at the top of the right eye and mouth

Sambucus, breathing through the cork layer

Cork is formed by a cambium layer that itself almost always arises as secondary meristem from the collenchyma or parenchyma layer directly under the epidermis. Unlike sclerenchymal cells, collenchymal cells are still alive and have retained the ability to differentiate. Cork cambium cells only divide periclinally, creating the typical rows of daughter cells. In this way mainly cork cells are produced to the outside and to a much lesser extent (sometimes not at all) cork parenchyma is produced to the inside. Cork cambium, cork cells and cork parenchyma together are also called periderm. Developed cork cells are dead and their cell walls contain suberine, a greasy substance that repels water.

A perfect sample for understanding the fine focus procedure: Pollen grains from Cobaea scandens

Cobaea Scandens (Jacob’s ladder family) is a widespread ornamental plant for garden and balcony. Domiciled in Mexico, this climbing plant is cultivated as an annual in the temperate zones.

Beside its aesthetics with bell-shaped violet flowers, there are two more aspects worth to mention:

• This plant is pollinated by bats. 
• Tthe large (~ 160 microns Ø) pollen grains of Cobaea show a complex structure which is worth to discover.

Pollen Grains in Brighfield

Breathing under water

Breathing:

Gills are the respiratory organs of many aquatic animals. With fish, the gills are in a space behind the head. Fishes exchange gasses with water through the gills.