No description available.

In 1984 and 1985 visual differences in frost damage were observed among 40 jojoba clones growing in a field in Tucson, Arizona. More detailed data were collected on the clone with the least damage (Clone-1) and the one with the most damage (Clone-2). On 10-ten terminal branch samples, Clone-1 showed an average of 12% leaf damage compared to 35% for Clone-2. Leaf freezing under controlled conditions on a monthly schedule showed that leaves of Clone-1 consistently froze at a lower temperature than Clone-2. Also, a second exotherm occurred in 50% of the samples for Clone-1 whereas a second exotherm occurred in only 15% of the samples of Clone-2. Soil moisture content and plant water potential were measured biweekly. Neither seemed to relate to the differences in freezing tolerance of the two clones. Total nonstructural carbohydrates (TNC), total soluble sugars, sucrose and proline were determined monthly. Accumulation patterns of TNC were similar for the two clones, however, Clone-1 generally accumulated more soluble sugars, sucrose and proline which might have contributed to its freezing tolerance. Growth measurements were recorded monthly to determine whether differences occurred between the two clones. Growth of both clones peaked in the spring, showed minor peaks in summer and ceased in winter. Under greenhouse conditions, pot grown cuttings from Clone-1 and Clone-2 were given zero, six or 12 gm of Osmocote fertilizer and watered at 35 or 70% field capacity to determine the effect of irrigation and fertilization on leaf freezing point. Fertilization significantly increased leaf concentrations of N and P and produced more growth. In the greenhouse study, no differences were found in leaf freezing point due to clones, irrigation or fertilization treatment. Leaves of Clone-1 froze at a higher temperature compared to field grown plants.

The objective of this study was to formulate a management system for improving early Quebec tomato yields through the use of polyethylene row tunnels and the screening of three tomato genotypes for their performance under a tunnel system of growing. / Three tomato (Lycopersicon esculentum Mill.) cultivars, Springset (early, cold-tolerant), Celebrity (standard), and Hope No. 1 (early, heat-tolerant), were grown under clear or white perforated polyethylene row tunnels that were either vented ten days prior to anthesis to maintain temperatures below 30$ sp circ$C or nonvented. Controls had no tunnel treatment. / Springset had the highest harvest index and subsequent highest early yield. Celebrity had the highest total yield. Hope was not suited to producing early yield under the frequent low temperature conditions occurring during the spring in Quebec. Tunnels did not improve early or total yield. / Further research is required before tunnels can be recommended for producing early tomatoes in Quebec.

Field experiments were established during the 1988 and 1989 growing seasons, to determine the effect of mini-tunnel management systems on floral development and fruit set of tomato (Lycopersicon esculentum Mill.). Two types of floral abnormalities reported to be caused by temperatures above 30$ sp circ$C were observed, namely: style exsertion and splitting of the antheridial cone. Clear vented and white non-vented mini-tunnels reduced the incidence of both these abnormalities compared to the controls in 1988. As a consequence these two types of mini-tunnels also had the greatest percentage fruit set and total marketable yield of the first three clusters. In 1989, none of the mini-tunnels tested significantly increased percentage fruit set or marketable yield. The cultivar Springset produced ripe fruits an average of 4 days before Hope#1 and 7 days before Celebrity in both 1988 and 1989.

The greatest weather enemy in all fruit destruction is the late spring frost which moves across the country under the high pressure areas that are occasionally seen on the weather maps, and kills the fruit buds.

No description available.

No description available.

With the high cost of maintaining and operating wind machines, growers are increasingly interested in alternative methods of freeze protection. Several possible frost protectant materials were applied to Valencia oranges at the Yuma Mesa Agricultural Center. Although temperatures reached the mid-to-upper 20s at the test site during the winters of 1984-1985 and 1985-1986, no frost damage occurred. As a result, it was impossible to evaluate the effectiveness of the materials.

No description available.

No description available.