Potato response to interacting conditions of nitrogen and water stresses and insect damage

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" Potato response to interacting conditions of nitrogen and water stresses and insect damage "
M. Ismail D. P. Kneivel

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112467
Doc. No	:	TLpq303717052
Main Entry	:	D. P. Kneivel
	:	M. Ismail
Title & Author	:	Potato response to interacting conditions of nitrogen and water stresses and insect damage\ M. IsmailD. P. Kneivel
College	:	The Pennsylvania State University
Date	:	1988
student score	:	1988
Degree	:	Ph.D.
Page No	:	154
Abstract	:	Greenhouse and field experiments were conducted to quantify and characterize potato (Solanum tuberosum L.) response to the interactive influences of nitrogen (N), water and Colorado Potato Beetle (CPB) defoliation stresses. Plants were subjected to N stress by applying N at 25% of the rate of a high N treatment (160 kg N and 140 kg N ha in greenhouse and field experiments, respectively) at the time of transplanting. Water stress and CPB defoliation stresses were imposed at tuber initiation. In the greenhouse biomass and leaf area data were analyzed by functional growth analysis techniques based on a thermal time unit. Maximum crop growth rate (CGR) was reduced 26% to 54% by N stress, 23% to 35% by water stress, and 6% to 8% by CPB defoliation. While the effect of N stress and CPB defoliation was mainly through reduction in light interception capacity of plants, water stress appeared to change CGR by net assimilation rate (NAR). Nitrogen and water stress increased C partitioning to tubers during the early growth stages. At the later growth stages the difference in C partitioning between the N treatments narrowed to 5% and 8% in the greenhouse in 1985 and 1986, respectively and 10% in the field in 1987. Nitrogen partitioning to tubers increased 17% and 5% due to N and water stresses, respectively. Defoliation stress did not alter partitioning of C or N. During the early growth stages stems and leaves function as sinks for total nonstructural carbohydrate (TNC) and N, respectively. Nitrogen stress did not affect stomatal resistance (rs) or apparent photosynthetic rate (P) per unit leaf area. The reduction in P due to water stress appeared to result from an increase in stomatal resistance as shown by a 78% increase in rs between stress and no stress treatments at the last sampling period. The presence of high N reduced the impact of water stress and CPB defoliation on all measured and derived growth parameters. These results indicate that high N fertility management should be practiced under low to moderate water stress conditions or high insect defoliation levels.
Subject	:	Agronomy
	:	Biological sciences