Friday , November 16 2018

Storage Organs

Many plants will reproduce themselves by their storage organs. The storage organs very and have diverse structures: bulbs, corms, rhizomes, root and stem tubers and turions. Most of the plants with storage organs will increase naturally by producing offsets. These should be lifted and divided to prevent overcrowding. The advantage of this type of propagation is that offsets will flower more quickly than seed-raised plants and the new plants will be identical with the parent plant, while seed-raised plants may vary in character from the mother plant.

Another way of propagation apart from division is to cut the storage organs into sections and to stimulate them to produce offsets by wounding. These sections or offsets will soon form complete plants if they are placed in right environment: a warm and dark place. Make sure you always dust the cut surfaces with a fungicide as they easily succumb to fungal attack.

Bulbs may be propagated by chipping, division of offsets, bulbils or bulblets, scaling or twin-scaling and scooping or scoring. You will decide in time, while you gain experience, which method works best for which bulb. Some plants will respond best to a specific method than any other.

Chipping – non-scaly or tunicate bulbs that do not increase quickly naturally may be multiplied rapidly by chipping. The method involves cutting each bulb into up to 20 pieces, depending on the size of the bulb. Each piece, which comprises three or more scale leaves and a section of basal plate, is then soaked in or dusted with a fungicide. The chips are then incubated or placed in vermiculite in a container in a frost-free greenhouse and left undisturbed. The new bulbs will form usually within 12 weeks but there are few that may take almost two years to develop. Separate the bulblets and repot or replant. This method is mostly used for snowdrops.

Division of offsets – bulbs have wide, fleshy scale leaves, which act as food storage organs. At their base are axillary buds, which may enlarge naturally to form offsets. When the bulbs are lifted at the end of their growing season, the offsets may be separated and planted out individually.

Bulbils or bulblets – bulbils are produced on flowerheads or stems and bulblets develop on the bulb itself or on stem roots. Both may be detached and planted up to develop into new bulbs.

Scaling – involves the removal of bulb scales. They are then induced to form bulblets. This method is used for bulbs that are made up of fairy loose scales. Individual scale leaves are pulled away from the basal plate of a mature bulb and then left in a plastic bag containing moist vermiculite or a peat-grit mix, in a warm, dark place. Bulblets appear at the scale bases usually after two months. Grow on the scales in a container until bulblets are large enough to be separated.

Twin-scaling – non-scaly or tunicate bulbs may be twin-scaled. By this, the bulb is cut vertically into 8-10 sections and each of these sections is then divided into pairs of bud scales with a small section of basal plate. These are then incubated and grown on in the same way as in scaling method.

Scooping and scoring – some bulbs can be propagate by scooping or scoring the bulb. This causes callus tissue to develop, which encourages bulblets to form. For scooping a bulb, the basal plate of a mature bulb is scooped out at the center, living just the outer edge of the basal plate intact. For scoring a bulb you made two shallow cuts at right angles into the basal plate. In both cases, the bulb is then stored basal plate uppermost, in a warm and dark place until bulblets have formed. Then detach them and grow them on separately.

These are reduced, compact, underground stems with a solid internal structure. Most corms produce several buds near the apex then each bud naturally form a new corm. Miniature corms or cormels are produced as offsets between the old and new corms in the growing season. You can increase artificially larger corms just before the growing season. Cut corms into pieces making sure each piece have a growing bud then dust the pieces with fungicide. Place them in a pot or open ground and lightly cover them with soil, while new corms develop. The method is mostly used for gladioli.

These consist of a horizontally growing shoot, usually beneath but sometimes on the soil surface. These can be propagated by cutting the rhizome into young and healthy sections, each with one or more growth buds, which are then planted up individually. Irises are one of the plants propagated by this method.

Root tubers
A root tuber is a portion of root at the stem base that swells during summer and is modified into a storage organ or tuber. They may be propagated in spring by dividing a cluster of tubers into smaller, healthy pieces, each of it having a developing shoot. The plants with root tubers can also be propagated by basal cuttings of the young, emerging shoots, in spring. This methods are mostly used for dahlias.

Stem tubers
Stems of some plants are modified to produce tubers, which act as storage organs. In spring you can cut these tubers into pieces making sure each has a growth bud, then dust them with fungicide. Each piece will produce basal shoots which can be used as basal cuttings or grow on to form a new tuber.

Other types of storage organs
Some plants, like Saxifraga granulate and some Kalanchoe and Asparagus species develop round, bulb-like buds in their shoot axils. These buds can be separated and grown on separately just like bulblets or cormels. In some water plants, like Hydrocharis and Myriophyllum, these relatively large bud structures are known as turions. When mature, they drop off the parent plant naturally, sink to the bottom of the water and develop into new plants.

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Many new propagation techniques have been introduced commercially since the mid 20th century. Some of these techniques are generally confined to laboratory nurseries because they are using advanced technologies, but the following developments affect several branches of horticulture and have direct or indirect relevance to gardening.

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