Nutrient uptake in cotton in relation to plant architecture
SummaryThe studies on uptake of nitrogen, phosphorus and potassium by two morphologically contrasting varieties of cotton MCU-1 and PRS-72 (bothGossypium hirsutum L.) at weekly intervals, showed that till the bursting of early formed bolls, the former type accumulated these nutrients in larger quantities in leaves and stem than in the fruiting parts unlike the latter type where differences in nutrient contents of these organs were very narrow till the active bolling phase. From flowering onwards, the fruiting parts of PRS-72 contained more phosphorus. Because of its bushy habit more dry matter accumulated and more nutrients remained unutilised in leaves and stem of MCU-1 at harvest compared with the short-branch variety PRS-72. Though both the varieties gave the same yield of seed cotton per unit area, PRS-72 removed considerably less quantities of nitrogen, phosphorus and pottassium. The short fruiting branch character in cotton therefore appears to contribute substantially towards balanced and economic utilization of nutrients.
Plant architecture influences growth and yield response of upland cotton to population density
Abstract Plant architectural characteristics directly affect inter-plant interactions and cotton crop management. Field studies were conducted in the 2010 and 2011 growing seasons at the University of Arizona Maricopa Agricultural Center to investigate the influence of plant architecture on the crop growth, biomass partitioning, and lint yield response of upland cotton to population density under irrigated desert conditions. Two cotton varieties of contrasting architecture, a tall stature columnar type, Delta and Pine 164B2RF (DP164), and a short stature bush type, Stoneville 4498B2F (ST4498), were evaluated under three plant population densities: low density (LD, 57,300–66,500 plants ha−1), medium density (MD, 77,300–109,800 plants ha−1), and high density (HD, 126,700–146,000 plants ha−1). While high population densities significantly increased plant height of both varieties at early growth stages, plant height at late growth stages were not significantly different. High plant population reduced main stem node number of both varieties. However, the effect was more pronounced with ST4498 where the HD treatment had 2.9 and 2.5 nodes less than the LD treatments in 2010 and 2011, respectively. Plant population affected the height to node ratio of DP164 more than ST4498. The taller, columnar type DP164 partitioned more biomass into stems than the bush type ST4498 at all three plant populations. The LD treatment significantly reduced cotton growth and yield of DP164 in 2010. This study suggests the existence of differences in responses to plant population density among upland cotton varieties, attributable to canopy architecture. Additionally, results indicate that shorter bush type varieties might have higher growth plasticity and thus accommodate a broader range of plant densities than taller stature columnar type varieties.
SUGAR MOVEMENT TO ROOTS, MINERAL UPTAKE, AND THE GROWTH CYCLE OF THE COTTON PLANT.
Comparative data .are reported in this paper oni the sugar concentrationls in the fibrous roots (and other parts) of defruited and control cotton plants and the uptake by these plants of bromine, nitrogen, and potassium. The measurements were made 22 days after defruiting (21 days after the addition of bromine to the nutrient solution). The data are discussed in terms of the relation of sugar concentrations in fibrous roots to mineral uptake and the relation of mineral uptake to the growth eyele of the cotton plant. The uptake of soil nutrients by the cotton plant, as shown by WHITE (27), CROWTHER (8, 9), DASTUR (10), OLsoN and BLEDSOE (23), and others, proceeds at an inereasing rate through the period of early growth and flowering but subsequently, as the niumber of bolls carried by the plants inereases, the rate of uptake deelilies anid actual losses of mineral elements from the above-ground portions of the plants mayoccur. It was suggested a niumber of vears ag,o (8) that the observed reduction in nitrogen uptake during the fruiting period of cotton might be due to depressed root growth. The dominance of fruiting activity over vegetative development and root growth has been well established in cotton (12, 13, 19, 20) and it seems certain that the extension of roots into new soil zones and the development of new root surfaces would be important factors in solute uptake. The foregoing explanation, however, insufficielntly accounts for all of the known facts. If, on the other hand, fruiting substantially reduces the concentration of sugars in the fibrous roots, the observed reduction in mineral uptake with fruiting can be more fully comprehended. The necessity for an expeniditure of energy for the accumulation of solutes against concentration differenitials has been outlined by HOAGLAND (17) and more recent work with barley seedlings (5) adds assurance that sugars situated in the roots provide the primary respiratory fuel for mineral uptake. It has been shown (18, 20) that the developing cotton boll tends to have first call on labile carbohydrates. Irrespective of probabilities, however, it has not been established that the sugar concentrations in fibrous roots vary enough with fruiting to constitute a critical intermediate link between fruiting and the rate of mineral uptake. The responses of soybeans (3) and of tomatoes (2) to defloration indicate that fruiting may alter the carbohydrate relations in the above-ground portions of plants without affecting imaterially the rate of mineral uptake. Two additional papers (24, 25) also pertain to the foregoing considerations. In soybeaiis, AUSTIN (3) founid the accumulation of some elements was depressed by defloration; his data show, however, that defloration had little