Iron

Iron [ Plant physiology - Chemistry ]
Abbreviation: Fe

Dictionary of botanic terminology - index of names

Iron deficiency [ Horticulture - Phytopathology ]


	Absence or insufficiency of iron needed for normal growth and development.

Iron deficiency , or lime-induced chlorosis, is often caused by an alkaline soil (high pH). As the pH of the soil increases above 6.0, the availability of iron to the plant gradually decreases. A wide range of ornamentals including both Australian native plant species and introduced species is affected by iron chlorosis . Importance of iron Iron is needed by all plants. It is an essential precursor for the formation of chlorophyll, which gives plant foliage its green colour. Chlorophyll is an active element in photosynthesis, a process which allows the plant to grow, mature and produce flowers. Iron is also important for normal activity of enzymes involved in plant respiration. Symptoms of iron deficiency Plant growth and vigour are reduced when the iron supply is limited. Since iron is not easily translocated within the plant, the symptoms of reduced green colour, due to less chlorophyll production, appear on the new leaves. The visual symptom on these new leaves is interveinal chlorosis, or yellowing of the plant between the leaf veins. In severe cases the entire leaf may be white. This symptom is similar to that caused by magnesium deficiency but iron deficiency is exhibited on the younger leaves, while magnesium deficiency is exhibited on the older leaves. Symptoms of iron deficiency tend to be more pronounced during winter. Causes of iron deficiency Iron deficiency does not only occur in alkaline soils but very often develops in acid soils, frequently limiting the growth of such acid-loving species as azaleas and rhododendrons. This condition may result from an accumulation of the heavy metals, copper, manganese and zinc, relative to the amount of iron present. Other factors, which may cause iron to become unavailable for plant use, are: high levels of calcium and magnesium carbonate overwatering of plants, causing poor aeration high or low temperature root damage large amounts of bicarbonate ions in soil solution or irrigation water high nitrate nitrogen in fertilisers high phosphate levels a deficiency of iron itself.

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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994