Faster Plant Growth Research Articles

Crescimento inicial do cafeeiro Rubi em resposta a doses de nitrogênio, fósforo e potássio e a regimes hídricos

O objetivo deste trabalho foi avaliar o crescimento da parte aérea do cafeeiro (Coffea arabica L.) cultivar Rubi MG 1192 submetido a três doses de N, P e K e dois regimes hídricos durante o primeiro ano após o transplante, em 20 de novembro de 2000. O crescimento da planta foi avaliado aos 134, 196, 236, 284, 334 e 383 dias após o transplante (dat). Houve resposta ao N e ao K no crescimento em número de ramos plagiotrópicos por planta, ao passo que no número de nós com gemas por planta, observou-se resposta apenas ao nitrogênio. Não houve resposta ao N, P e K no aumento da massa seca da parte aérea e no índice de área foliar. Além de mostrar efeito significativo no crescimento do cafeeiro, a irrigação antecipou o rápido crescimento para julho (236 dat) proporcionando plantas mais vigorosas. Nas plantas não-irrigadas, o rápido crescimento ocorreu em meados de outubro (334 dat). Entretanto, a irrigação não impediu a queda na taxa de crescimento durante o inverno. O desenvolvimento das gemas em frutos ou ramos secundários nas plantas não-irrigadas alterou a distribuição de matéria seca e reduziu o crescimento do caule, ramos e folhas.

Tree regeneration patterns on Mount Usu, northern Japan, since the 1977?78 eruptions

Although the summit of Mount Usu was deforested by the 1977–78 eruptions, vegetative regeneration on the caldera rim was rapid due to the erosion of thick volcanic deposits by snow and rain. To obtain the mechanisms underlying regeneration patterns after the eruptions, we monitored the growth of permanently-marked stems from 1983 to 1990. Regeneration was from resprouting-branches buried in the volcanic deposits on the caldera rim, while on the crater basin, where thick volcanic deposits accumulated, regeneration was from seedlings. The seedling regeneration lagged approximately 3 years behind vegetative regeneration. Stem densities averaged 14,000 ha-1 in the vegetatively-regenerated community on the caldera rim, and 28,000 ha-1 in the seedling regeneration on the crater basin. Populus maximowiczii accounted for ca. 75% of total stems on the caldera rim, while P. maximowiczii accounted for ca. 30% on the crater basin where Salix integra and Betula platyphylla var. japonica were also common. In both stands, immigration and mortality rates were very low. The growth of vegetatively regenerated stems expressed as stem height and diameter was significantly faster than that of stems grown from seedlings. Herbivory damage on the terminal shoots of tall stems was restricted on the caldera rim and was restricted for B. platyphylla var. japonica on the crater basin, perhaps due to fast growth supporting herbivore avoidance or low palatability. Height growth was restricted when neighbors established in close proximity, especially in the seedling-regenerated forest. The results suggest that vegetative regeneration is rapid due to three mechanisms: 1) faster plant growth; 2) herbivore avoidance; and 3) decreased interference by neighboring.

Effects of an organic sediment on performance of young Phragmites australis clones at different water depth treatments

Performance of young Phragmites australis plants was examined after 7 weeks on an artificial nutrient-enriched inorganic substrate and on the same substrate to which an organic sediment from a eutrophic lake was added, at three different water depth treatments. Growth decreased, and proportional allocation of biomass to roots increased, with the addition of sediment. These differences were significant in shallow and deep water, but not at a medium depth. Concentrations of phosphorus and nitrogen in plant biomass decreased, and concentration of iron increased, with addition of sediment. The effects of sediment addition may have resulted from a decreased availability of nutrients in the substrate or from an impaired root functioning. Nutrient exhaustion in the substrate, due to a fast plant growth, can explain the relatively strong effects in shallow water. Deep water, on the other hand, probably restricted oxygen transport to the roots, resulting in an impaired root functioning in the low-redox sediment environment. The results show that, especially in relatively deep water, growth of undisturbed plants of P. australis may be inhibited by eutrophication of sediments, probably because of an impaired root functioning in sediments containing reduced toxic compounds (e.g. ferrous iron).

EFFECT OF LIME RATES ON NUTRIENT AVAILABILTY, MOBILITY, AND UPTAKE DURING THE SOYBEAN-GROWING SEASON

Soil acidity, associated with elemental deficiencies and toxicities, is a limiting factor in southern agriculture. It is related to the predominance of highly weathered and leached clayey and coarse-textured soils. Liming is an essential practice, and research has been done to elucidate the relationships among liming, soil acidity, and plant growth. However, there is a need to continue to quantify the impact of liming on reducing toxic levels of Al and Mn, on increasing nutrient availability and mobility, and on nutrient uptake during the growing season by determinate soybean varieties. The main objective of this study was to determine the effect of lime levels and time on nutrient availability, mobility, and uptake during the entire soybean growing season, under field conditions. Liming with the recommended rate of 3000 kg/ha was sufficient for optimum soybean yields and seed composition. It also increased soil pH from 5.1 to 5.9 within 4 wk, decreased the exchangeable Al from 29 to 3 ppm within 6 wk, reduced the extractable Mn from 23 to 15 ppm within 6 wk, and increased the extractable P from 3 to 51 ppm within 4 wk. Shoot Al concentrations decreased after week 4 with the onset of exponential growth, despite increasing accumulation rates. Total shoot Al increased after week 4 with plant growth and in spite of decreasing Al concentrations. The daily Al accumulation rate in the shoots increased from week 4 to week 12 in association with fast plant growth and available B horizon Al, despite decreasing Al in the A horizon. The Al accumulation rate decreased to-ward the end of the growing season in association with slow plant growth and loss of roots and root activity. Similar results were observed for Mn and P.