Publication Date
1997
Description
An increase in the photosynthetic rate of the remaining tissues or regrowth has been proposed to explain compensatory growth after defoliation. In fact, we observed this effect in guineagrass, but it was not solely related to higher stomatal conductance. Nitrogen and irradiance may influence this response in the field, interacting with clipping. The objective of this research was to determine if these factors alter photosynthesis of intensively clipped well-watered guineagrass. Plants grown in a soil mixture were placed in the shade and in full sunlight. After establishment, some plants in each irradiance were clipped monthly at 20-cm, and the others left unclipped . Half of the plants in each irradiance and clipping regime were extra fertilized monthly using urea. With the clipped-off tissue, leaf area was measured, oven dried and weighed to obtain biomass. Samples were selected to analyze soluble sugar, starch, and total non-structural carbohydrates (TNC). A factorial 22x4 in a split plot completely randomized design was used. With the residual plants, photosynthesis and stomatal conductance were measured. In the final harvest biomass data was also obtained and a completely randomized 23 factorial arrangement was applied. In the clipped-off tissues significant differences were found for the biomass increments due to the nitrogen treatments, but not to irradiance regimes. Leaf area was more responsive to irradiance. In full sunlight, residual biomass was greatest using extra fertilization, both in unclipped and clipped plants. Clipped plants had higher photosynthesis than unclipped ones in the sun, and extra urea decreased this effect. Shaded guineagrass showing lower photosynthesis were not affected by clipping. Extra nitrogen applied in the shade alter only unclipped plants. When residual biomass and the clipped off tissues were added together, it was seen that clipping decreased total yield. In full sun, nitrogen fertilization reduced photosynthesis and stomatal conductance and increased chlorophyll both in clipped and unclipped plants. Higher photosynthesis in these well-watered plants was related with higher stomatal conductance, and higher yield with extra nitrogen.
Citation
Paez, A; Gonzalez, M E.; Villavicencio, L; Salazar, A; and Tissue, D, "Interpreting Guineagrass Behaviour Under Different Clipping, Nitrogen and Irradiance RegimesA" (2024). IGC Proceedings (1997-2023). 46.
https://uknowledge.uky.edu/igc/1997/session22/46
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Interpreting Guineagrass Behaviour Under Different Clipping, Nitrogen and Irradiance RegimesA
An increase in the photosynthetic rate of the remaining tissues or regrowth has been proposed to explain compensatory growth after defoliation. In fact, we observed this effect in guineagrass, but it was not solely related to higher stomatal conductance. Nitrogen and irradiance may influence this response in the field, interacting with clipping. The objective of this research was to determine if these factors alter photosynthesis of intensively clipped well-watered guineagrass. Plants grown in a soil mixture were placed in the shade and in full sunlight. After establishment, some plants in each irradiance were clipped monthly at 20-cm, and the others left unclipped . Half of the plants in each irradiance and clipping regime were extra fertilized monthly using urea. With the clipped-off tissue, leaf area was measured, oven dried and weighed to obtain biomass. Samples were selected to analyze soluble sugar, starch, and total non-structural carbohydrates (TNC). A factorial 22x4 in a split plot completely randomized design was used. With the residual plants, photosynthesis and stomatal conductance were measured. In the final harvest biomass data was also obtained and a completely randomized 23 factorial arrangement was applied. In the clipped-off tissues significant differences were found for the biomass increments due to the nitrogen treatments, but not to irradiance regimes. Leaf area was more responsive to irradiance. In full sunlight, residual biomass was greatest using extra fertilization, both in unclipped and clipped plants. Clipped plants had higher photosynthesis than unclipped ones in the sun, and extra urea decreased this effect. Shaded guineagrass showing lower photosynthesis were not affected by clipping. Extra nitrogen applied in the shade alter only unclipped plants. When residual biomass and the clipped off tissues were added together, it was seen that clipping decreased total yield. In full sun, nitrogen fertilization reduced photosynthesis and stomatal conductance and increased chlorophyll both in clipped and unclipped plants. Higher photosynthesis in these well-watered plants was related with higher stomatal conductance, and higher yield with extra nitrogen.
