iPhoneOgraphy – 10 Nov 2016 (Day 315/366)
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. Roots can also be aerial or aerating, that is growing up above the ground or especially above water. Furthermore, a stem normally occurring below ground is not exceptional either (see rhizome). Therefore, the root is best defined as the non-leaf, non-nodes bearing parts of the plant’s body. However, important internal structural differences between stems and roots exist.
Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids, tropical coastal swamp trees such as mangroves, the resourceful banyan trees, the warm-temperate rainforest rātā (Metrosideris robusta) and pōhutukawa (M. excelsa) trees of New Zealand and vines such as Common Ivy (Hedera helix) and poison ivy (Toxicodendron radicans).
Aerial roots may receive water and nutrient intake from the air. There are many types of aerial roots, some such as mangrove aerial roots, are used for aeration and not for water absorption. In other cases they are used mainly for structure, and in order to reach the surface. Many plants rely on the leaf system for gathering the water into pockets, or onto scales. These roots function as terrestrial roots do.
Most aerial roots directly absorb the moisture from fog or humid air.
Some surprising results in studies on aerial roots of Orchids show that the ‘Velamen’ – the white spongy envelop of the aerial roots, are actually totally water proof, preventing water loss but not allowing any water in. Once reaching and touching a surface the Velamen is not produced in the contact area, allowing the root to absorb water like terrestrial roots.
Many other Epiphytes – non-parasitic or semi-parasitic plants living on the surface of other plants, have developed cups and scales that gather rainwater or dew. The aerial roots in this case work as regular surface roots. There are also several types of roots creating a cushion where a high humidity is retained.
Some of the aerial roots, especially in the Tillandsia genus, have a physiology that collects water from humidity, and absorbs it directly.
The fossil record of roots – or rather, infilled voids where roots rotted after death – spans back to the late Silurian. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows. They can be discriminated using a range of features.
iPhoneOgraphy – 30 Sep 2016 (Day 274/366)
The vascular cambium (plural cambia) is a plant tissue located between the xylem and the phloem in the stem but not in the root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith [material at the center of plant, often dead and/or deteriorated, that is composed of parenchyma tissue]) and the secondary phloem growth (outwards [to the bark, rough or smooth, of the plant]). It is a cylinder of unspecialized meristem cells that divide to give new cells which then specialize to form secondary vascular tissues.
Vascular cambia are found in dicots and gymnosperms but not monocots, which usually lack secondary growth. A few leaf types also have a vascular cambium.Vascular cambium does not transport water, minerals, or dissolved food through the plant. It does, however, produce the phloem and xylem, which do perform these functions.
For successful grafting, the vascular cambia of the rootstock and scion must be aligned so they can grow together. In wood, the vascular cambium is the obvious line separating the bark and wood.
The cambium present between primary xylem and primary phloem is called intrafasicular cambium. At the time of secondary growth, cells of meduallary rays, in a line with intrafasicular cambium, become meristematic and form interfascicular cambium. The intrafascicular and interfascicular cambiums, therefore, represent a continuous ring which bisects the primary xylem and primary phloem and is known as cambium ring. The vascular cambium then produces secondary xylem on the inside of the ring, and secondary phloem on the outside, pushing the primary xylem and phloem apart.
Shot & Edited using iPhone 6+
A parasitic plant is one that derives some or all of its nutritional requirements from another living plant. All parasitic plants have special organs, named haustoria (singular: haustorium), which connect them to the conductive system of their host and provide them with the ability to extract water and nutrient from the hosts. About 4,100 species in approximately 19 families of flowering plants are known. Parasitic plants have a modified root, the haustorium, that penetrates the host plant and connects to the xylem, phloem, or both.
F/4, 1/8 sec, ISO – 800, Photoshop CS6