Drought is a significant factor limiting crop production in arid regions while hawthorns (Crataegus sp.) are an important component of such region’s forests. Therefore, treatments that increase hawthorn drought resistance may also increase transplanting success. Thus, the physiological and biochemical responses of hawthorn seedlings to a factorial combination of different concentrations of silica nanoparticles (SNPs at 0, 10, 50 and 100 mg L−1) and three soil moisture treatments (without stress, moderate stress and severe stress) were investigated. Seedlings were irrigated with one of the four concentrations of SNPs for 45 days before exposing them to drought stress. Photosynthesis parameters, malondialdehyde (MDA), relative water content (RWC), membrane electrolyte leakage (ELI) as well as chlorophyll, carotenoid, carbohydrate and proline content were determined. At the end of the experiment, positive effects by SNP pre-treatment on physiological indexes were observed during drought stress. Under drought conditions, the effect of SNPs on photosynthetic rate and stomatal conductance was evident. Although the SNPs increased plant biomass, xylem water potential and MDA content, especially under drought conditions, RWC and ELI were not affected by the SNP pre-treatments. Seedlings pre-treated with SNPs had a decreased carbohydrate and proline content under all water regimes, but especially so under drought. Total chlorophyll content and carotenoid content did not change among the treatments. Generally, the findings imply that SNPs play a positive role in maintaining critical physiological and biochemical functions in hawthorn seedlings under drought stress conditions. However, more studies are needed before the physiological and biochemical basis of induced drought resistance can be determined.

Container production has many advantages over traditional in-ground (field) production, including less damage occurring to the root system when transplanted, better establishment after transplanting, decreased labor and land acquisition costs for production, and increased product availability and longevity in the retail market. Growing plants in containers, however, alters root growth and function and can change root morphology. Numerous factors influence root growth in containers. Roots of container-grown plants are subjected to temperature and moisture extremes not normally found in field production. The effects of substrate aeration (Ea) as well as water holding capacity (Pv) interact with different pot characteristics, resulting in changes to root morphology. Successful plant establishment after transplanting is often linked to root health. This review focuses on the roles of substrate physical and chemical properties, container characteristics, and temperature in altering root growth in container-grown woody nursery crops. Root circling, planting too deeply or “too-deep syndrome” (TDS), and the use of composts as container substrates will also be examined.

One-year-old red oak seedlings (Quercusrubra L.) from three open-pollinated families were produced in 1 m tall containers during 1989. In spring 1990, the seedlings were either transplanted (which included pruning the main root to a 15-cm length) or not. Transplanted seedlings either received a 5-s basal dip in 20 mM indole-3-butyric acid or did not. The seedlings were placed in a greenhouse and harvested at the beginning of the first lag phase, at the beginning of elongation of the second growth flush, and 70 days after the beginning of the experiment. Root-pruning removed 42 to 50% of whole-plant dry weight. Transplanted seedlings had significantly reduced leaf surface area and began a second growth flush later than untransplanted seedlings. There were no treatment differences in CO2 assimilation rate on a per unit leaf surface area. Predawn xylem water potential in transplanted seedlings was lower than in untransplanted seedlings. Transplanted seedlings used less root and more shoot reserves to develop the first flush than untransplanted seedlings. Treating root-pruned seedlings with 20 mM indole-3-butyric acid did not significantly increase growth potential compared with untreated transplanted seedlings. For transplanted red oak, transplant shock seems to be mediated through reduced leaf surface area, which reduces whole-plant water use.

Seedlings of nine coarse-rooted species–sawtooth oak (Quercus acutissima Carruth), white oak (Q. alba L.), cherrybark oak (Q. falcata var. pagodifolia Elliott), post oak (Q. stellata Wangenh.), black walnut (Juglans nigra L.), pignut hickory [Carya glabra (Mill.) Sweet], pecan [C. illinoinensis (Wangenh.) C. Koch], Chinese chestnut (Castanea mollissima Blume), and common baldcypress [Taxodium distichum (L.) L. Rich]—were grown for one growing season in nontreated containers or in containers treated on their interior surfaces with white interior latex paint containing 100 g Cu(OH)2/liter. Seedlings of each species and container treatment were harvested twice: once after being transplanted from 3.2- to 15.0-liter containers and at the end of the growing season. Cupric hydroxide-treated containers decreased the amount of circled, kinked, and matted roots formed at the container wall-medium interface in all species tested. Plants grown in Cu(OH)2-treated containers also had altered root dry-weight partitioning. The partitioning patterns were species specific and included 6% to 20% increases in the percentage of root dry weight in interior vs. exterior portions of the rootball (white oak, black walnut, Chinese chestnut, and baldcypress), 10% to 21% increases in the percentage of root dry weight in upper vs. lower halves of the rootball (sawtooth oak, cherrybark oak, black walnut, and baldcypress), and an increase in the percentage of primary lateral roots (lateral roots originating from taproots or roots functioning as taproots) on the upper (proximal) half of taproots (cherrybark oak, pecan, and baldcypress). Nutrients in leaves, stems, and roots of sawtooth oak seedlings were analyzed at both harvests. Seedlings grown in Cu(OH)2-treated containers had more Cu in most plant tissues than nontreated seedlings. Also, seedlings grown in Cu(OH)2-treated containers had higher total Ca and Mg concentrations at transplanting and higher total N and Zn concentrations at the end of the growing season than nontreated seedlings.

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