Suman Singha

Changes in nutrient composition and pH of the culture medium during in vitro shoot proliferation of crabapple and pear

Shoot tips of Seckel pear and Almey crabapple were cultured on liquid MS medium containing 8.8 μM BA. Changes in shoot proliferation and growth and in nutrient and carbohydrate composition of the medium were determined during a 9 week culture period. Whereas shoot proliferation in crabapple increased linearly during the culture period, it levelled off after week 4 in pear. Explant dry weight in both genera showed a linear increase over time. Culture medium pH decreased in the initial weeks and increased thereafter. There was a rapid decline in medium P and Fe concentration with both genera and of Zn in the medium of crabapple. In no instance did the rate of depletion of any nutrient from the medium of pear cultures exceed that measured in the crabapple medium. The decline in sucrose concentration in the medium was similar for both genera and was accompanied by an increase in the level of glucose and fructose. At the end of the culture period slightly over half of the initial carbohydrate level remained in the medium.

Relationship between calcium and agar on vitrification and shoot-tip necrosis of quince (Cydonia oblonga Mill.) shoots in vitro

Shoot-tip cultures of Quince C (Cydonia oblonga Mill.) initiated on Murashige & Skoog (MS) medium containing 5 μM BA and 0.6% Phytagar showed both shoot-tip necrosis and severe vitrification. Culturing explants on medium containing 1.2% Phytagar and Ca levels of 3 mM (MS medium), 18 mM and 30 mM showed a decrease in growth with increasing medium Ca levels, being especially severe at 30 mM. The Ca content of the explants increased linearly with increasing medium Ca. Culturing explants on medium containing 3 mM, 9 mM, and 18 mM Ca at 0.6, 0.9, and 1.2% agar resulted in reduction in growth, shoot-tip necrosis, and vitrification when either factor was increased. The reduction in shoot-tip necrosis could be accounted for primarily by an increase in medium Ca levels but may also be affected by a change in explant growth. Increasing Ca concentration in the medium resulted in a linear increase in explant K, Ca, Mg, and B levels and a decrease in Mn and Na. Although increasing medium Ca or agar levels reduced vitrification, it is unclear whether they were the direct cause of the reduction in vitrification or whether this response was an effect of the reduction in culture fresh weight.

Tissue culture propagation of running buffalo clover (Trifolium stoloniferum Muhl. ex A. Eaton)

Rapid propagation of running buffalo clover (Trifolium stoloniferum) was achieved on Murashige & Skoog (MS) medium. Excellent shoot proliferation and shoot growth were obtained on medium containing 0.5 or 1 mg l-1 BA. In vitro proliferated shoots were rooted on MS or half-strength MS medium containing 0 to 0.4 mg l-1 IAA. Both the number of roots initiated and the length of the longest root were significantly higher on MS medium than on half-strength MS medium. Rooted plantlets were successfully transferred to soil.

Agar Induced Variations on the Nutritional Composition of Pear and Crabapple Shoots in vitro

The objective of this investigation was to determine whether nutritional differences in explants on media solidified with 3 agar brands would explain agar-induced variations in proliferation and growth responses. Shoot-tips of ‘Almey’ crabapple and’ seckel’ pear were cultured on Murashige and Skoog (MS) salt mixture supplemented with 10 mg/1 myo-inositol, 0.4 mg/1 thiamine, 30 g/1 sucrose, and 2 mg/1 N -benzyladenine (BA). Media were solidified with either Bacto-agar, Phytagar, or T.C. agar at concentrations ranging from 0.3 to 1.2%. A liquid medium treatment was used to obtain a comparative benchmark for expiant nutrient levels. Expiant nutrient levels determined after 8 weeks were influenced both by agar brand and concentration. Although large differences in a number of elements occur both in agar brands and in expiants cultured on media containing similar concentrations of these brands, variations in proliferation and growth cannot be explained based on differences in individual elements. From a nutritional standpoint, modification of the elemental composition of the basal medium may be one cause of the growth variations induced by different agar brands.