The need for reforestation in cork oak （Quercus suber L.） areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings. We evaluated the early development of cork oak seedlings treated using tree shelters and mulching in northwestern Tunisia. We tested three tree shelter treatments （non-vented, vented, and control） to shield seedlings from animal damage and five mulch types to control competing vegetation （Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk （organic mulches）, gravel （inorganic mulch） and no mulch）. At the end of the two-year experiment, sheltered seedlings were 89-99% taller than unshelteredseedlings and had higher numbers and lengths of shoot growth flushes. In contrast, both stem diameter growth and dry weight biomass （from samples extracted after two years） were significantly reduced inside tree shelters. Root-to-shoot ratio was not significantly different in sheltered vs. unsheltered seedlings, suggesting that tree shelters do not adversely affect this parameter. Mulching alone did not favour growth, but could be beneficial when combined with tree shelters. The combination of vented tree shelters and gravel mulch was the most effective treatment for promoting diameter, height and stem volume growth.
We investigated the combined effects of soil moisture and light intensity on the growth, development and ecophysiological characteristics of one-year old Amorpha fruticosa seedlings. Soil moisture and light intensity influenced the ecophysiological characteristics of Amorpha fruticosa seedlings. Soil moisture resulted in the decreases of growth rate, individual size, net photosynthetic rate, transpiration rate, leaf water loss rate （WLR）, and biomass accumulation of plant parts, and led to increased leaf water saturation deficit （WSD）. Under water stress, more photosynthetic products were allocated to root growth. With decreasing light intensity, net photosynthetic rate, transpiration rate, chla/b, water saturation deficit, water use efficiency, water loss rate and biomass accumulation declined, while Chla, Chlb, Chla＋b and carotenoids （Car） increased and more photosynthetic products were allocated to stem and leaf growth. Maximum growth vigor, net photosynthetic rate and total biomass accumulation in Amorpha fruticosa seedlings was recorded at 75 80% soil water-holding capacity and 100% light density in greenhouse environments.
In this article,we investigated effects of lead and cadmium on the biomass of ginkgo seedlings, and roles of the seedlings in accumulation characteristics of the heavy metals and remediation of the soil contaminated by Cd2+ or Pb2+ as well as their combination.The results showed that both Cd2+ and Pb2+ significantly or very significantly reduced biomass increment of ginkgo seedlings,with Pb2+ more adverse than Cd2+.The Cd2+-Pb2+ compound pollution further reduced biomass increment of ginkgo seedlings.The mass fractions and enrichment coefficient of Pb2+ and Cd2+ in ginkgo seedlings were in an order of root>stem>leaf,which was in favor of transportation Pb2+ and Cd2+ from root to stem and leave.The Cd2+-Pb2+ compound pollution promoted ginkgo seedling absorption to Cd2+ and Pb2+.The capacity of the upward transport of Pb2+ was greater than that of Cd2+,which suggested an obvious dose-effect and synergistic effect.Cd2+ and Pb2+ accumulations in ginkgo seedlings were relatively large.The accumulation in roots was higher than that in stems and leaves.The ability of the absorption,transportation and accumulation of ginkgo seedlings to Pb2+ was relatively greater under Cd2+-Pb2+ compound pollution.The phytoremediation efficiency of Cd2+ and Pb2+ was relatively high.
The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly lower than in the bulk soil.However,the addition of NH4- -N significantly decreased the pH value in the root-soil interface and the addition of No3 -N slightly increased the pH value in the root-soil interface.The magnitude of pH changes in the root-soil interface depended upon the concentrations of the nitrogen sources added.The contents of Ca2-P,Fe-P and Al-P in the root-soil interface were much lower after treated with NH4 -N and slightly higher after treated with No3 -N compared with control treatment.After treated with 100,200 and 400 mg·kg-1NH4+ -N,the deficiency rates of Ca2-P in the area 0-1 mm from the root plane were 37.1%,45.9%and 57.7%,respectively,the deficiency rates of Fe-P were 23.4%,29.1%and 38.2%,respectively,and the deficiency rates of Al-P were 25.1%,28.0%and 33.2%,respectively. Compared with the control the deficiency rates of Ca8-P in NH4+ -N and No3-N treatments decreased and increased,respectively,but the differences were not obvious.The contents of Ca10 -P and O-P in the root-soil interface did not significantly change after treated with NH4+ -N or No3 -N,suggesting that Ca10- P and O-P were remarkably difficult to be mobilized even at the presence of high concentration of NH4+ -N.The lowered pH in the root-soil interface induced by the addition of the NH4 -N promoted the transformation of phosphates in the root-soil interface,enhanced the mobilization and bioavailability of phosphates,and thereby remarkably increased the absorption of phosphorus by roots.
Determining the influences of environmental factors on seedling growth and leaf color may improve our understanding of the chromogenic mechanisms in leaves and the biosynthesis of anthocyanin. To determine the optimum conditions for Betula 'Royal Frost' seedling cultivation,we assessed seedling growth and anthocyanin content under natural conditions. The temperature had a significant influence on height but not on radial growth.Between June and September, the anthocyanin content was significantly positively correlated with light intensity and air moisture and significantly negatively correlated with temperature. In single-factor experiments to determine the variation in anthocyanin content in the greenhouse, anthocyanin content increased with increasing soil water content and at first increased, then decreased with increasing pH of the irrigation water and temperature, but decreased with increasing light intensity. K2SO4 can increase the anthocyanin content. So to maintain leaf color, seedlings should be cultivated with\200 lmol m-2 s-1 light intensity at 20 _C and soil moisture content between 60 and 90%, and the irrigation water should be neutral or alkaline. Additionally,spraying with K2SO4 can be beneficial.