The development of the tuber in seedlings of five species of Dioscorea from Nigeria

Abstract

Tubers in all five species develop from the hypocotyl region of the seedlingS. A perivascular cambium arises cutting off mainly starch‐storing parenchyma and collateral vascular bundles to the inside. A phellogen gives rise to cork on the outside. Between the two cambial layers there may or may not be layers of parenchyma, not storing starch but containing raphides. The vascular bundles consist of xylem with vessels, scalariform tracheids and parenchyma; and phloem, with sieve tubes and parenchyma.

Dynamics of Amyloplast Sedimentation in Growing Yam Tubers and Its Possible Role in Graviperception

“…However, it has not been reported that independent tissue like root caps is formed at the tips of the tubers in Dioscorea. In fi ve species of Dioscorea, the fi rst indication of tuberization was the formation of perivascular cambium in the hypocotyl region, and the shape of the tuber depended on the local persistence of meristematic zone (Lawton and Lawton, 1969). In Dioscorea cayenensisDioscorea rotundata complex, the subapical meristematic zone is formed at the apex of tuber (Trouslot et al, 1993).…”

“…is a kind of yams and the tuber growing underground is used mainly as food. Organographically, the tuber of Dioscorea is generally regarded as a stem tuber (Burkill, 1960;Lawton and Lawton, 1969) but has some characteristics different from the potato (Solanum tuberosum) and other conventional stem tubers. In yam tubers, the surface is devoid of scale leaves and identifi able nodes.…”

“…Previous investigations have supported that amyloplasts in columella cells within the root cap at the apical parts of the root plays an important role in gravitropism (Juniper, 1976;Kiss et al, 1989Kiss et al, , 1996Sack, 1997;Morita and Abe, 1999;Kiss et al, 2002). The origin and development of tubers in several Dioscorea have been investigated by anatomical and morphological methods (Lawton and Lawton, 1969;Sharma, 1974;Trouslot et al, 1993). However, to our knowledge, the formation of the independent tissue like root cap at the tips of the tubers has not been described and the mechanism of gravitropism of tubers in Dioscorea has not been discussed.…”

Improving the application of gibberellic acid to prolong dormancy of yam tubers (Dioscorea spp)

“…9 -12 In view of the influence of sprouting on postharvest losses, efforts have been made to prolong dormancy by applying sprout regulators (reviewed by Barker et al 9 ). The most promising, affordable and reliable active compound is gibberellic acid (GA 3 ). 15,16 The established method of application is that used by Martin,14 in which tubers are de-cormed and soaked for varying lengths of time in a solution of 150 to 500 mg kg −1 of GA 3 .…”

“…The most promising, affordable and reliable active compound is gibberellic acid (GA 3 ). 15,16 The established method of application is that used by Martin,14 in which tubers are de-cormed and soaked for varying lengths of time in a solution of 150 to 500 mg kg −1 of GA 3 . The immersion period was reduced drastically from 22 h to between 2 and 6 h. 17 -19 Instead of treating the whole tuber, dipping the apex proved to be sufficient.…”