EFFECTS OF AN ANTI-GIBBERELLIN GROWTH RETARDANT ON GROWTH RESPONSES OF POTATO NODAL STEM SEGMENTS CULTURED IN VITRO

Foliage of non-induced `Katahdin' potato plants was treated with BAS-111. Other plants were sprayed with GA3 solution and placed in an inducing chamber. All treatments were repeated the following week. After final treatment, apical, sub-apical, medial, and basal nodal stem segments were taken from each plant, surface-sterilized, and placed on MS culture media. After 3 weeks in a darkened incubator, cultures were examined. Induced plants produced 5.5 times more tubers than did non-induced segments. BAS-111 applied to non-induced plants was associated with 63% reduction in rhizome length and 3.2-fold increase in tuber number. GA treatment to induce plants resulted in improved rhizome elongation, delayed and reduced tuberization when compared with control explants. Lower nodes produced more and larger tubers than did younger tissues. Results will be discussed in light of current literature.

EFFECT OF ANTI-GIBBERELLIN GROWTH RETARDANTS ON TUBERIZATION OF `KATAHDIN' POTATO LEAF BUD CUTTINGS.

Non-induced Katahdin potato plants were treated with three anti-gibberellins: CCC, BAS-106 and BAS-111. Other plants were sprayed with GA3 and placed in an inducing chamber. All treatments were repeated the following week. After final treatment, apical, sub-apical, medial and basal leaf bud-cuttings were taken from each plant and placed 1n a mist chamber. After two weeks, cuttings were examined for tuberization. BAS-111 and CCC were associated with 3.5 and 2 fold increase, respectively, in tuberization of cuttings over the non-induced control. Although induced control cuttings exhibited 100% tuberization, application of GA to plants grown under identical conditions, reduced tuberization 20 fold. In non-induced control cuttings and those treated with CCC, basal cuttings tuberized significantly better than those taken from higher on the stem. This pattern was reversed for plants treated with BAS-111. These results will be discussed in light of current understanding of the tuberization phenomenon.

An assessment of the modifying effect of kinetin on in vitro tuberization of induced and non-induced tissues of Solatium tuberosum

‘Katahdin’ potato plants (Solatium tuberosum L.) were grown under inducing (26 °C day −12 °C night with an 8-h photoperiod) and non-inducing (28 °C day −25 °C night with a 16-h photoperiod) conditions. Apical, medial, and basal nodal stem segments from each plant harvested were surface sterilized and aseptically transferred to culture flasks containing Murashige and Skoog's medium with and without kinetin. After culturing in dark for 4 weeks at 24 °C, percentage tuberization of segments from induced plants was significantly greater than for non-induced segments. Addition of kinetin to the culture medium eliminated this effect of induction. Apical segments from induced plants tuberized more frequently than those from non-induced plants and those from lower on stem. Addition of kinetin eliminated this stem position effect. Percentage elongation was significantly greater in segments from non-induced than induced plants. Addition of kinetin reduced percentage elongation in non-induced segments to that for induced segments. Percentage elongation was greatest in apical segments from non-induced plants and this position effect could be eliminated by addition of kinetin.

INFLUENCE OF MANGANESE CONCENTRATION IN NUTRIENT SOLUTION ON THE GROWTH AND ELEMENTAL CONTENT OF THE "KATAHDIN" POTATO PLANT

Hoagland’s solutions containing nine levels of manganese ranging from 0 to 100 ppm were applied as a drench tri-weekly to potato plants (Solanum tuberosum L. cv. Katahdin) growing in perlite. Although no deficiency symptoms were observed during the 48-day growing period, varying degrees of toxicity were associated with concentrations of 25.0 ppm Mn and higher in nutrient solution. The tissue concentration necessary to induce toxicity symptoms in foliage appeared to fall between 134 and 426 ppm Mn. Solution concentrations in excess of 25 ppm Mn caused a significant reduction in dry weight of top, root and rhizome portions, and in rhizome number. Increasing Mn treatments generally influenced elemental tissue content as follows: K and Mn increased, Mg decreased, Al and Ca decreased at and above 50 ppm and 75 ppm Mn, respectively, whereas P increased at 50 ppm Mn and above; B, Cu and Mo were unaffected and although N, Fe and Zn contents were somewhat erratic, they were not significantly different at 100 ppm Mn from the control (0.50 ppm Mn).

OCCURRENCE OF AMINO ACIDS IN THE HONEYDEW OF THE CRESCENT-MARKED LILY APHID, MYZUS CIRCUMFLEXUS (BUCK.)

The honeydew of Myzus circumflexus feeding on Katahdin potato contains 22 free amino acids and amides, which are given in their respective amounts. Carbohydrates constitute also an important portion of this product of digestion in aphids. Analyses of amino compounds in honeydew may be of prime importance in the study of the causes of plant resistance to aphids.