Unlike many cereal and vegetable crop plants, apple trees grown from seed of a variety will not produce fruit of that variety. Due to its heterozygous inheritance pattern, each apple variety must be propagated or increased by vegetative means. Since most fruiting varieties of apple do not root readily from cuttings, it is customary to graft them upon the root of another apple tree grown for the purpose. The latter is known horticulturally as a rootstock while the fruiting variety that is grafted on it may be termed the scion.

No description available.

No description available.

The many medicinal, nutritional, industrial, and agricultural uses of moringa are well documented, although studies remain focused on moringa as a wild, uncultivated plant and little horticultural research has been devoted to its culture. Greenhouse experiments were conducted at the State University of New York at Cobleskill, New York, USA during the summer of 2006. Soilless culture has been investigated as an alternative production system for medicinal and aromatic plants, and moringa seedlings were grown using hydroponic and aeroponic culture at a pH of 5.5-6.0 and electrical conductivity levels of 2.0-2.3 dS˙m-1 in order to maximize leaf biomass production and gain access to root biomass. Moringa leaves are valued for their human nutritional benefits and as a livestock feed, however the monopodial growth habit of moringa requires removal of the terminal growing point in order to encourage branching and maximize leaf production. Seedlings are often subjected to extreme levels of vegetative harvest when grown in high-density agroforestry production systems, often resulting in high levels of mortality. Seedling decapitation induced outgrowth of lateral buds, and no lateral buds were released by intact plants that were not decapitated. The release from apical dominance was repressible by the application of exogenous auxin (0.5% IAA) to the stumps of decapitated seedlings. Seedlings decapitated to node 6 (15 cm, counted acropetally) released buds more quickly and produced three times the dry weight per plant than seedlings decapitated to node 1 (5 cm). Seedlings decapitated to 30 cm (approximately 12 nodes) released 2 more buds per plant and twice the dry weight compared to those decapitated to 40 cm (approximately 16 nodes). Pinching seedlings to remove 5 or 10 cm of apical stem resulted in little regrowth with few buds released and low dry weights. The percentage of stem removed was more important than the actual height to which a seedling was decapitated in order to maximize regrowth. Twice-decapitated plants released more buds (6.7/plant) than once-decapitated plants (2.7/plant), demonstrating enhanced lateral bud response of previously decapitated seedlings. The effect of four different pruning strategies on leaf biomass production of young, pollarded moringa trees was also examined.

<p> Almond water use was investigated at the leaf, plant and canopy level under a range of irrigation conditions in commercial orchards in California. Understanding plant response to water stress, specifically the behavior of plant transpiration and water use during periods of water stress, has important implications for irrigation scheduling in agriculture but also for water resources management and policy making. </p><p> Leaf gas exchange measurements of stomatal conductance and photosynthetic rate were performed at midday on shaded and on sunlit leaves, with midday stem water potential used to assess plant water stress. An essentially linear decline in both photosynthetic rate (from 25 to 5 &mu;mol m^-2 s^-1) and stomatal conductance (from 400 to 50 mmol m^-2 s^-1) as stem water potential declined over the range of -0.5 to -3 MPa was observed in sunlit leaves. These data indicated a strong sensitivity of leaf-level physiological processes to water stress. However, evapotranspiration at the canopy level, measured using Eddy Covariance, did not show a reduction relative to atmospheric demand during periods of water stress. The apparent disconnect observed between leaf conductance, responsive to water stress and canopy evapotranspiration, insensitive to water stress, is the central problem investigated in this study.</p><p> When the transpiration data was analyzed in the framework of a "Big Leaf" model, decoupled conditions (i.e. a limited stomatal control of transpiration) were shown to prevail at the experimental site, contrary to previous findings reported in the literature for tall crops such as almond orchards. Low coupling implies only a moderate sensitivity of transpiration to stomatal closure. Measured coupling increased substantially with wind speed but showed a wide range of values at the low wind speeds (&lt;1m s^-1) that were observed at the site. At any wind speed however, higher canopy resistance resulted in higher coupling. The high leaf area index observed in the orchard may have been responsible for causing decoupled conditions, because when leaf area decreased as a result of harvesting operations, canopy transpiration appeared to become more sensitive to water stress. </p><p> Cumulative daily sap velocity was used as an estimate of plant transpiration. At the plant level, contrasting behaviors were observed in plant transpiration in the presence of water stress, depending on the duration and intensity of the stress. During long soil dry-down periods encompassing several weeks, plant transpiration relative to the evaporative demand of the atmosphere showed a statistically significant decline associated with a decrease in stem water potential and in stomatal closure. However, when the cycle of water stress was short (days), reductions in stem water potential seemed to be associated with an increase in cumulative sapflow velocity. The analysis of these results led to the development of a simple model that describes the theoretical interactions between three dependent variables, namely stem water potential, stomatal conductance and transpiration. The model output suggested that in wet soil, an increase in transpiration may be caused by increasing evaporative demand even if stem water potential and stomatal conductance decrease.</p>

A new, uncomplicated system for the forced ventilation of plants and cultures has been investigated in terms of both its efficiency of ventilation and its effects on the growth and physiology of various plant species, including cauliflower, tobacco, Annona (custard apple) and potato. This new system, which has no moving parts or artificial energy requirement, provides a sustained, pressurised stream of sterile, humidified air (RH = 70-94%) driven by humidity-induced diffusion. This process depends upon the maintenance of a gradient of water vapour across a microporous partition for inducing the diffusion of air into the apparatus. Flows up to 5 cm³ min¯¹ can be produced and the atmosphere in a 60 cm³ culture vessel can be renewed every 12 min Compared to the standard conventional diffusive method of ventilation, e. g. by capping the vessel with a polypropylene disc, this new system has proved to be 18X more efficient in removing accumulated ethylene and in keeping CO₂ and O₂ levels in culture vessels close to atmospheric. This forced ventilation system has also been shown to be very effective in the in vitro cultivation of seedlings or cuttings of cauliflower, tobacco, Annona and potato for improving growth and preventing symptoms of vitrification such as leaf epinasty, reduction of leaf area and production of abnormal stomata. In potato cuttings the induction and production of microtubers have been promoted and the growth of abnormal callus prevented. In Annona cuttings flower bud production, leaf and shoot growth and micropropagation have been promoted and leaf and flower bud abscission have been reduced. In cauliflower, tobacco and Annona the leaf chlorophyll contents, rates of photosynthesis and yields were improved by this forced ventilation. These beneficial effects have been variously attributed to the efficient removal of ethylene, the maintenance of near to atmospheric levels of CO₂ and O₂ by day and night and to the reduction of humidity levels in the vessels to below 100% RH. It is hoped that this new ventilation system, which is comparatively inexpensive and requires very little maintenance might have some useful applications in the field of tissue culture and perhaps particularly in developing countries.