Abstract
All the plants exhibit tolerance to stress due to external environmental factors, but with inter-species variation in intensity. The objective of the study was to comparatively evaluate morphological and anatomical modification in different plant cultivars under similar water stress condition and their possible impact on physiological processes affecting their growth performance. The investigation was done in terms of morphological modifications, change in leaf anatomy, water status and productivity. The experiment was done under rainfed condition in northeastern India in three selected cultivars of Gladiolus. All parameters were measured using standard procedures. Stomatal density was found to decrease with water stress with lowest value in cultivar Aarti (122.2 mm-2) while stomatal size (length=7.3µm and breadth=7.00µm) and pore size (3.66µm2) was found to be highest in cultivar Aarti that account for its better photosynthesis rate and growth. The thickness and number of epidermal cells were found to be highest in Aarti that help them to comparatively better amelioration of moisture stress effect. The cultivar Aarti also had higher numbers and size of xylem and phloem that indicate greater unloading of carbohydrate to sink region following increase of sink size. The highest water saturation deficit was found in cultivar Apollo (36.02%) that account for its decline in stomatal conductance, reduction of stomatal size, transpiration and saturation deficit. Comparatively higher leaf area duration (116 days) and net assimilation rate (1.62 g cm-2day-1x10-3) of cultivar Aarti attributed to its higher biomass production with larger spike size with good numbers of flowers. The highest marketable spikes (71111.11 per ha) was found in cultivar Aarti which might be due to its comparatively less deviation, during stress condition, from normal morphological and anatomical characteristics. The tolerant cultivars are those that can adapt to the change without much change in their normal growth. And the responses of those species are commercially acceptable that promote adaptation without compromising much with the plant growth and crop production.
Highlights
The performance of cultivars of any crop species has interregional variation under a given set of agro-climatic conditions and was estimated to be reduced by 69% on average when plants are exposed to unfavorable environment[1]
The highest staomatal density was observed in the cultivar Apollo (148.2 mm-2) and lowest in Aarti (122.2 mm-2) under similar water stress conditions
Previous studies indicate that generally high positive correlation between water stress and stomatal length and pore size20, . 21,22,23 Generally it was observed that CO2 diffusion is facilitated by greater stomatal size[24], because of the fact that the conductance was found to be proportional to the square of the effective radius of the stomatal spore, leading to an increased stomatal conductance level[25]
Summary
The performance of cultivars of any crop species has interregional variation under a given set of agro-climatic conditions and was estimated to be reduced by 69% on average when plants are exposed to unfavorable environment[1]. Out of various environmental factors effecting the crop production and productivity, available water is the most crucial. Water deficit have negative impact on plant growth and reproduction due to its influence on many cellular and whole plant functions[2]. The impact of water deficit on plant physiology, morphology and anatomy were well documented3, . 4,5,6,7 Influence of water deficit stress can be seen in various levels of plant growth- micro and macro levels[8,9], inhabiting various physiological and biochemical processes including photosynthesis, respiration, translocation, ion uptake, carbohydrates, nutrient metabolism, and hormones[10,11,12,13]. The effect of water stress is most severe during growing season and adversely impact crop production[4].
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