appear insensitive to dynamic changes in rates of growth. The seasonal dynamics of leaf area were discussed previously ( Blom and Tarara, 2007 ), in which a logistic function provided a better estimate of leaf area as a function of thermal time than did a
Gypsophila paniculata . Therefore, we examined the seasonal variations in the growth and development of four different cultivars of Gypsophila paniculata . Our results showed that Gypsophila paniculata is season-sensitive, and that some cultivars cannot
flower yield was less than one flower per year ( Higaki et al., 1992 ) or two flowers per year ( Dufour and Guérin, 2005 ). Development and growth of Anthurium were significantly affected by seasonal fluctuations ( Klapwijk and van der Spek, 1988 ; van
Asparagus officinalis L. cv. Centennial established with seedling transplants in 1983 was maintained with a conventional tillage (CT) or a no-till) (NT) system with either metribuzin or metribuzin + napropamide being applied for weed control. Marketable yield was assessed from 1985-1989. In 1989, in addition to yield data, destructive harvests were made every three weeks from March to November to evaluate the effects of tillage on fern, crown and bud growth and root carbohydrate levels. Yields were reduced in CT when compared to NT during all years. Asparagus growth (crown and fern weight, bud cluster, bud and fern numbers) was greater in NT than CT throughout the year although seasonal patterns of growth were similar for both tillage systems. Root carbohydrate levels were higher in NT than CT before the harvest season began. Carbohydrates for both tillage systems reached their lowest level in late July before recovering to pre-harvest levels in late September. Use of metribuzin + napropamide did not reduce fern number or yield but significantly reduced the number of bud clusters, buds and fern when compared to metribuzin alone.
growth were calculated as the difference between the final and initial measurements. The height growth was normalized to relative height growth (RHG) by dividing each seasonal change in height by the initial height as follows: where ΔH/Δt is the change in
been reported to provide 50% to 70% of diffused solar insolation to the tea cultivation area ( Lehlohonolo et al., 2013 ). Shade netting has been used in normal tea plantation in major tea producing areas to enhance optimum growth and productivity
Flowers and stems (cladodes) of cactus pear [Opuntia ficus-indica (L.) Mill.] appear simultaneously in spring, and a second vegetative and reproductive flush can be obtained in early summer by completely removing flowers and cladodes of the spring flush at bloom time. The seasonal growth patterns of cactus pear fruits and cladodes were examined in terms of dry-weight accumulation and cladode extension (surface area) to determine if cladodes are competitive sinks during fruit development. Thermal time was calculated in terms of growing degree hours (GDH) accumulated from bud burst until fruit harvest. Fruits of the spring flush had a 25% lower dry weight and a shorter development period than the summer flush fruits, and, particularly, a shorter duration and a lower growth rate at the stage when most of the core development occurred. The duration of the fruit development period was better explained in terms of thermal rather than chronological time. The number of days required to reach commercial harvest maturity changed with the time of bud burst, but the thermal time (40 × 103 GDH) did not. Newly developing cladodes may become competitive sinks for resource allocation during most of fruit growth, as indicated by the cladode's higher absolute growth rate, and the fruit had the highest growth rate during the final swell of the core, corresponding to a consistent reduction in cladode growth rate. Cladode surface area extension in the first flush ceased at the time of summer fruit harvest (20 Aug.), while cladodes continued to increase in dry weight and thickness until the end of the growing season (November), and, eventually, during winter. The growth of fruit and cladodes of the summer flush occurred simultaneously over the course of the season; the cladodes had a similar surface area and a lower (25%) dry-weight accumulation and thickness than did first flush cladodes. The proportion of annual aboveground dry matter allocated to the fruits was 35% for the spring flush and 46% for the summer flush, being similar to harvest increment values reported for other fruit crops, such as peach [Prunus persica (L.) Batsch.]. Summer cladode pruning and fruit thinning should be accomplished early in the season to avoid resource-limited growth conditions that could reduce fruit and cladode growth potential.
Abstract
Changes in susceptibility to chilling injury of grapefruit (Citrus paradisi MacF.) were found to vary directly with the growth activity of the trees. Exogenous growth regulators were applied to test the hypothesis that they may be involved in seasonal variations in susceptibility to chilling injury. Benzyladenine, gibberellic acid and 2,4-dichlorophenoxyacetic acid applied postharvest and benzyladenine and 2,4-D applied preharvest significantly altered susceptibility to chilling injury although the direction and extent of the changes were neither consistent nor predictable.
73 ORAL SESSION (Abstr. 457-464) FRUIT CROPS: GROWTH AND DEVELOPMENT II
Abstract
Root growth of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] and bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Davy] (C-4 plants), show distinct seasonal patterns different from those of the cool-season perennial grasses (C-3 plants). Root growth continued after winter shoot dormancy occurred, and at soil temperatures below 10°C. Severe browning of the entire root system was observed just after spring shoot greenup followed by a delay of about 3 weeks in new root initiation and replacement, even though significant shoot development was occurring prior to this period of root initiation.