Evaluation of Drought Stress on Growth Analysis
in Autumnal Rape Seed (Brassica Napus L.) Cultivars

A. Malek Sabet¹*, A. Mehrabi ², A. H. Shiranirad ³

¹Research and Science Unit, Islamic Azad University, Karaj, Iran
e-mail: ali_malek14@yahoo.com

² Department of Agronomy, Islamic Azad University, Varamin, Iran
³ Seed and Plant Improvement Institute, Karaj, Iran

Abstract

The great part of rapeseed production is done under dry farming conditions; therefore, the plant reaction to water stress is considered an important matter. In order to study the drought stress effects on yield and yield component of in autumnal Rapeseed cultivars (Brassica napus L.) a field experiment was conducted as factorial arranged in a randomized complete block design with four replications in 2002/3 of Karaj. There were two factors, irrigation at two levels (80 percent of evaporation as control and drought stress from stem elongation stage) as first factor and cultivars in 11 levels: Sw.0756, Modena, Geronimo, Elite, Opera, ARC-5, ARC-91004, ARC-4, ARC-2, Digger and SLM046 as control. The results of growth analysis indicated that drought stress caused reduction of dry matter, leaf area index (LAI), crop growth rate (CGR), and net assimilation rate (NAR). Growth index that contains LAI, CGR, NAR and RGR was conducted. In this experiment for formulated test and variance analyze used MSTATC software. The result of this research showed that the maximum of LAI in water stress condition so obtain the maximum CGR was achieved in 3_4/5 that occurred in  1908 until 2100 GDD. Enhance of LAI on dry stress condition is unfavorable because that cause lose available water for root consume. The maximum of LAI was obtained in 189_218 day after planting on dry stress conditions for cultivars. Elite and Modena cultivars on dry stress condition with maintenance of LAI could confirm by that conditions and produced proper yields. Maximum of CGR had exactly obtained whit LAI increase and in 1710-1908 GDD (189-203 day after planting) and after that CGR was decreased because of leaves canopies and decrease photosynthesis activities of down leaves. Maximum NAR on dry stress conditions in 1075 GDD (94 day after planting) was related Digger cultivars by 3/93 g.m2.10 gdd and minimum NAR on this time was related SLM046 cultivars by g/m2.10 gdd. In majority of cultivars on dry stress conditions after stemming stage and with decrease of CGR or LAI, NAR was reduced that this condition in sensitive cultivars was obvious. The maximum of RGR was related to Digger cultivars with 0/02 g/g.10gdd but the minimum was related to ARC-5 cultivars with 0/012 g/g.10 gdd (with this GDD).

Keywords: Autumnal rapeseed, Growth analysis, Drought stress, Iran