Various abiotic stresses affect growth and development of plants and two important cues that cause to sever decrease the horticultural and crops yield are the heat and chilling stresses worldwide. Plants have various mechanisms to tolerate or avoid the stresses; one of these mechanisms is the biosynthesis of organic solutes. In this paper, effects of chilling (0-15 °C) stress on the horticultural (ornamental and vegetable) plants and crops are discussed. You will see that plants how to tolerate the stress by organic solutes. The most important organic molecules to regulate water relations in plants are introduced. The organic solutes that also are called osmo-protectants include soluble carbohydrates, amino acids and nitrogen compounds.

Various abiotic stresses affect growth and development of plants and one of them that causes severely decreasing the horticultural and crop yields is the heat stress worldwide. In this paper, the effects of heat (more than 30-35 °C in different species) stress on the horticultural plants and crops, and its effects on inducing other stresses, including osmotic and oxidative stresses are discussed. Plants show the molecular and biochemical responses after receiving environmental signals such as high temperatures and tolerate undesirable conditions.

In bulb production period, the promotion of photosynthesis and, consequently, increased synthesis of carbohydrates have the particular importance to enhance the size and quality of the bulbs. The aim of this study was to investigate the effects of chitosan and magnetism on the synthesis of photosynthetic compounds. Magnetic nano-composite (MN) and carboxymethyl chitosan (CM) during the production period of yearling bulblet were used as experimental materials. The results showed that MN (15 mg L^-1) had the highest effects on the amounts of photosynthetic pigments. Compared to other treatments, this treatment had the highest effect on starch, while the soluble carbohydrates and amylase activities showed the highest amount with CM (5 to 15 mg L^-1). However, due to the importance of starch in bulb size and quality, MN with a concentration of 15 mg L^-1 is recommended.