Gary A. Couvillon
Several studies with annual crops have shown that large seeds improve percent germination, seedling growth, and uniformity, yield, seedling vigor, and stress tolerance. Little information is available on the influence of seed size on the resulting seedlings of woody plant species. Cercis canadensis L. seeds were divided into large and small seed size fractions and the seeds scarified, stratified, and planted. A larger percentage of large seeds germinated than did small seeds. Seedlings from large seeds had a greater peak and germination value than small seeds, indicating greater vigor and a more rapid germination rate thus more uniform seedlings. Seedlings from large seeds, as indicated by fresh and dry weights, were larger and contained a greater leaf area than those produced by small seed.
Gary A. Couvillon
Leaves from several own-rooted peach cultivars [Prunus persica (L.) Batsch] were found to contain higher Ca and Mg concentrations than leaves of the same cultivars budded to several peach seedling rootstocks. Own-rooted ‘Loring’ cuttings had a higher leaf N content than ‘Loring’ on ‘Nemaguard’; and in 1 year out of 2, own-rooted ‘Redhaven’ trees had higher leaf N concentrations than ‘Redhaven’ on ‘Bailey’ rootstocks.
Gary A. Couvillon and A. Erez
Rooted ‘Redhaven’ peach [Prunus persica (L.) Batsch] cuttings were exposed to diurnal temperature cycles. A severe reduction in lateral vegetative bud break was found in plants refrigerated at 4°C and given 8 hr daily exposure to 19° (±0.1°). Nearly complete chilling negation occurred in plants exposed to diurnal cycles including 8 hr of 20° or 21°. Also, effect decreased with increased time (0 to 8 hr per day) of exposure to 24°. Buds on plants exposed to cycles including 20° for 2 and 4 hr showed no chilling negation, but gradual increases in chilling negation occurred with longer exposures to 20°. ‘Harvester’ peach plants were exposed to 2, 7, or 12 days of 23° following the accumulation of one-fourth, one-half, or three-fourths of the chilling requirement. Chilling negation occurred only with the 12-day exposure to 23° when high temperatures were applied following the accumulation of one-fourth and one-half of the chilling requirement. No chilling negation was found after 12 days’ exposure to 23° if three-fourths of the chilling requirement had accumulated before exposure.
Gary A. Couvillon and A. Erez
Shoots of apple (Malus domestica Borkh.), cherry (Prunus avium L.), peach [Prunus persica (L.) Batsch] and pear [Pyrus communis × Pyrus pyrifolia (Burm.) Nakai] were collected and used in these studies. In all instances, chilling beyond that required for 50% bud break within a 2-week period (prolonged chilling) resulted in a decrease in the growing degree hours required for bud break. In many cases, over 90% of the variation in each study could be attributed to the added chilling.
Hening Hu and Gary A. Couvillon
The activities of catalase and of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), the two key enzymes in the pentose phosphate pathway (ppp), were measured in the seeds of Prunus persica (L.) Batsch var. nectarina Maxim `Nectarine 7'. The seeds were subjected to three imbibition treatments: 1) continuous 24C; 2) continuous 4C; and 3) application of thiourea (TU)/gibberellic acid (GA) at various concentrations to seed held at 24C then subsequently chilled at 4C. Treatments of continuous 24 or 4C indicated that catalase, G6PDH, and 6PGDH exhibited significant activity increases only when the seeds obtained germination potential, which occurred in the seeds chilled for 7 weeks at 4C. Seeds held at 24C did not germinate and showed little change with time in G6PDH and 6PGDH activity. There was only a slight increase in catalase activity beginning 3 weeks following treatment initiation and a decrease in activity following 13 weeks of treatment. Thiourea treatment resulted in an inhibition of catalase activity and a stimulation of G6PDH, but had no effect on 6PGDH activity. However, no correlation between enzymic activity and seed germination was found. The results strongly questioned the role of the ppp and catalase activity in dormancy control as previously hypothesized.
Edmond Ganjeh and Gary A. Couvillon
Plants of tomato (Lycopersicon esculentum Mill. cv. Manalucie) grown in wire mesh cylindrical enclosures (cages) produced fruit with greater soluble solids content when cage diameter increased from 31 to 62 cm. Cage diameter or height did not influence juice pH, color, yield, or harvest labor input.
Donald A. Lloyd II and Gary A. Couvillon
Three-year-old peach trees were manually defoliated on 6 successive biweekly dates starting in mid July of 1972. Approximately 30 days after treatment, flowers were forced. Flowers produced on 7/8 and 8/1 treatment trees were atypical, whereas flowers forced on 9/12 and 9/26 treatment trees were apparently normal. Defoliation on 8/15 and 8/29 produced flowers both atypical and normal types. The number of forced flowers, adjusted with trunk diameter, increased with each successive defoliation date although the number of flowers forced on any date was small. Floral abnormalities consisted of large leaf-like sepals without petioles, flowers with poorly colored petals, and exerted stigmas. Some abnormal flowers set fruit.
Vegetative bud break decreased with each successive defoliation date. Neither vegetative nor flower buds were forced when individual shoots were defoliated rather than whole trees.
Gary A. Couvillon and Donald A. Lloyd II
Peach (Prunus persica (L.) Batsch) trees defoliated from mid-July to late September of 1972 were observed in March of 1973. There was a relationship between foliation following defoliation and bloom delay the following spring. Trees defoliated on or before August 15, 1972 bloomed later than those not defoliated or trees defoliated after that date. Trees defoliated on August 29 were intermediate in bloom delay and trees defoliated later bloomed with the control. Vegetative shoot length on trees defoliated on July 18 was less than that from trees defoliated on August 1 which was less than trees defoliated on August 15. Other treatments did not differ in vegetative shoot length from the control.
Gary A. Couvillon and T. O. M. Nakayama
‘Concord’ grape vines trained to the Modified Munson and 4-arm Kniffin systems were sampled, at weekly intervals, beginning approximately one month before harvest and continuing to harvest. The fruit were categorized for evenness of ripening and analyzed for total pigment content and per cent soluble solids. Total yield, and components of yield were compared under the 2 training systems.
Fruit harvested from the Modified Munson trained vines ripened more evenly, contained more anthocyanin pigments, soluble solids, and produced greater yields than did vines trained to the 4-arm Kniffin system. The yield increase was due to increases in the percentage of fruiting shoots, clusters per shoot, and cluster weights on vines trained to the Modified Munson system. The increase in cluster weight was due to increases in berry weight and berries per cluster.